Since the original identification of Schimmelpenning syndrome, the number of findings has expanded to the point that the syndrome is associated with a considerable constellation of abnormalities. The abnormalities may occur in a variety of combinations, and need not include all three aspects of the classic triad of sebaceous nevus, seizures and mental retardation. In 1998, a literature review by van de Warrenburg et al. found:

- seizures in 67% of cases

- mental retardation in 61% of cases

- ophthalmological abnormalities in 59% of cases

- involvement of other organ systems in 61% of cases

- structural abnormality of cerebrum or cranium in 72% of cases

The major neurological abnormalities include mental retardation to varying extent, seizures, and hemiparesis. Seizures, when present, typically begin during the first year of life. The most common structural central nervous system abnormalities in Schimmelpenning syndrome are hemimegalencephaly and ipselateral gyral malformations.

The major ocular abnormalities are colobomas and choristomas.

Skeletal abnormalities may include dental irregularities, scoliosis, vitamin D-resistant rickets and hypophosphatemia. Cardiovascular abnormalities include ventricular septal defect and co-arctation of the aorta; urinary system issues include horseshoe kidney and duplicated urinary collection system.

Schimmelpenning syndrome is a neurocutaneous condition characterized by one or more sebaceous nevi, usually appearing on the face or scalp, associated with anomalies of the central nervous system, ocular system, skeletal system, cardiovascular system, and genitourinary system.

Synonyms include: "Linear nevus sebaceous syndrome (LNSS)", "Schimmelpenning-Feuerstein-Mims syndrome", "Feuerstein-Mims syndrome", "sebaceous nevus syndrome", "Solomon syndrome", and "Jadassohn's nevus phakomatosis". "Nevus" is sometimes spelled "naevus" and "sebaceous" may also be spelled "sebaceus". "Epidermal nevus syndrome" is sometimes used as a synonym, but more often as a broader term referring to Schimmelpenning syndrome in addition to nevus comedonicus syndrome, CHILD syndrome, Becker's nevus syndrome, and phakomatosis pigmentokeratotica.

The classic Schimmelpenning syndrome diagnosis comprises a triad of sebaceous nevi, seizures, and mental retardation. The condition was first reported by Gustav Schimmelpenning in 1957 and independently reported by Feuerstein and Mims in 1962.

Phakomatosis pigmentovascularis is subdivided into five types:

- Type 1 PWS + epidermal nevus

- Type 2 (most common): PWS + dermal melanocytosis +/- nevus anemicus

- Type 3: PWS + nevus spilus +/- nevus anemicus

- Type 4: PWS + nevus spilus + dermal melanocytosis +/- nevus anemicus

- Type 5: CMTC (Cutis marmorata telangiectatica congenita) + dermal melanocytosis

They all can contain capillary malformation. Type 2 is the most common and can be associated with granular cell tumor. Some further subdivide each type into categories A & B; with A representing oculocutaneous involvement and subtype B representing extra oculocutaneous involvement. Others have proposed fewer subtypes but currently this rare entity is mostly taught as having five subtypes currently.

Phakomatosis pigmentovascularis is a rare neurocutanous condition where there is coexistence of a capillary malformation (port-wine stain) with various melanocytic lesions, including dermal melanocytosis (Mongolian spots), nevus spilus, and nevus of Ota.

Phakomatosis pigmentokeratotica is a rare neurocutanous condition characterized by the combination of an organoid sebaceous nevus and speckled lentiginous nevus. It is an unusual variant of epidermal naevus syndrome. It was first described by Happle "et al". It is often associated with neurological or skeletal anomalies such as hemiatrophy, dysaesthesia and hyperhidrosis in a segmental pattern, mild mental retardation, seizures, deafness, ptosis and strabismus.

VHL disease can be subdivided according to the clinical manifestations, although these groups often correlate with certain types of mutations present in the VHL gene.

Signs and symptoms associated with VHL disease include headaches, problems with balance and walking, dizziness, weakness of the limbs, vision problems, and high blood pressure. Conditions associated with VHL disease include angiomatosis, hemangioblastomas, pheochromocytoma, renal cell carcinoma, pancreatic cysts (pancreatic serous cystadenoma), endolymphatic sac tumor, and bilateral papillary cystadenomas of the epididymis (men) or broad ligament of the uterus (women). Angiomatosis occurs in 37.2% of patients presenting with VHL disease and usually occurs in the retina. As a result, loss of vision is very common. However, other organs can be affected: strokes, heart attacks, and cardiovascular disease are common additional symptoms. Approximately 40% of VHL disease presents with CNS hemangioblastomas and they are present in around 60-80%. Spinal hemangioblastomas are found in 13-59% of VHL disease and are specific because 80% are found in VHL disease. Although all of these tumours are common in VHL disease, around half of cases present with only one tumour type.

Abdallat–Davis–Farrage syndrome is a form of phakomatosis, a disease of the central nervous system accompanied by skin abnormalities. It is characterized by the out of the ordinary pigment of skin that is abnormal to one's genetics or the color perceived on a basis..

The condition is named after the team of medical professionals who first wrote it up, describing the appearance of the syndrome in a family from Jordan. It was characterized in 1980 by Adnan Abdallat, a Jordanian doctor.

The syndrome is thought to be inherited as an autosomal recessive genetic trait, meaning that in order to manifest symptoms, a person must inherit a gene for Abdallat–Davis–Farrage syndrome from both parents. As it is also autosomal (not linked to either of the genes that determine gender), it can manifest in both men and women. Those with only one gene are carriers, and they typically manifest no symptoms; in the event that a person inherits both genes, symptoms usually appear before one year of age.

Many conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment. The skin weighs an average of four kilograms, covers an area of two square meters, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin. Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands form from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.

The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. Nourishment is provided to these layers by diffusion from the dermis, since the epidermis is without direct blood supply. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95 percent of the epidermis. This stratified squamous epithelium is maintained by cell division within the stratum basale, in which differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where cells are continually shed from the surface. In normal skin, the rate of production equals the rate of loss; about two weeks are needed for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. The superficial papillary dermis with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. Structural components of the dermis are collagen, elastic fibers, and ground substance. Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands. The dermis contains two vascular networks that run parallel to the skin surface—one superficial and one deep plexus—which are connected by vertical communicating vessels. The function of blood vessels within the dermis is fourfold: to supply nutrition, to regulate temperature, to modulate inflammation, and to participate in wound healing.

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia. This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.

Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on. Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow). Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.

A DNA repair-deficiency disorder is a medical condition due to reduced functionality of DNA repair.

DNA repair defects can cause an accelerated aging disease or an increased risk of cancer, or sometimes both.

Megalencephaly-capillary (MCAP) is one of the two major syndromes of megalencephaly. Typically, MCAP and MPPH can be distinguished by somatic features. MCAP includes many characteristics that are observed at birth including: cutaneous vascular malformations, especially capillary malformations of the face and cutis marmorata, polydactyly, connective tissue dysplasia, and focal or segmental body overgrowth. Furthermore, MCAP can occasionally be linked with asymmetric brain overgrowth (hemimegalencephaly) as well as segmental overgrowth of the body (hemihypertrophy).

"Life-threatening disease redirects here".

A systemic disease is one that affects a number of organs and tissues, or affects the body as a whole.

Hemimegalencephaly is an extremely rare form of macrocephaly and is characterized by uneven development of brain hemispheres (one-half of brain is larger than other). The syndrome can be presented by itself or in association with phakomatosis or hemigigantism. Additionally, hemimegalencephaly will frequently cause severe epilepsy, focal neuro-logical deficits, macrocrania, and mild to severe mental retardation.

A wide variety of symptoms are potential clinical features of ciliopathy.

- Chemosensation abnormalities, typically via ciliated epithelial cellular dysfunction.

- Defective thermosensation or mechanosensation, often via ciliated epithelial cellular dysfunction.

- Cellular motility dysfunction

- Issues with displacement of extracellular fluid

- Paracrine signal transduction abnormalities

In organisms of normal health, cilia are critical for:

- development

- homeostasis

- reproduction

DNA repair defects are seen in nearly all of the diseases described as accelerated aging disease, in which various tissues, organs or systems of the human body age prematurely. Because the accelerated aging diseases display different aspects of aging, but never every aspect, they are often called segmental progerias by biogerontologists.

A histiocytoma in the dog is a benign tumor. It is an abnormal growth in the skin of histiocytes (histiocytosis), a cell that is part of the immune system. A similar disease in humans, Hashimoto-Pritzker disease, is also a Langerhans cell histiocytosis. Dog breeds that may be more at risk for this tumor include Bulldogs, American Pit Bull Terriers, American Staffordshire Terriers, Scottish Terriers, Greyhounds, Boxers, and Boston Terriers. They also rarely occur in goats and cattle.

A ciliopathy is a genetic disorder of the cellular cilia or the cilia anchoring structures, the basal bodies, or of ciliary function.

Although ciliopathies are usually considered to involve proteins that localize to motile and/or immotile (primary) cilia or centrosomes, it is possible for ciliopathies to be associated with proteins such as XPNPEP3, which localizes to mitochondria but is believed to affect ciliary function through proteolytic cleavage of ciliary proteins.

Significant advances in understanding the importance of cilia were made beginning in the mid-1990s. However, the physiological role that this organelle plays in most tissues remains elusive. Additional studies of how ciliary dysfunction can lead to such severe disease and developmental pathologies is a subject of current research.

Hair diseases are disorders primarily associated with the follicles of the hair.

A few examples are

- Alopecia

- Bubble hair deformity

- Hair casts

- Hair loss

- hypertrichosis

- Ingrown hair

- Monilethrix

- Premature greying of hair

- Pattern hair loss

- Trichorrhexis invaginata

Many hair diseases can be associated with distinct underlying disorders.

Piedra are fungal diseases.

Hair disease may refer to excessive shedding or baldness (or both). Balding can be localised or diffuse, scarring or non-scarring. Increased hair can be due to hormonal factors (hirsutism) or non-hormonal (hypertrichosis). Scalp disorders may or may not be associated with hair loss.

Getting a regular eye exam may play a role in identifying the signs of some systemic diseases. "The eye is composed of many different types of tissue. This unique feature makes the eye susceptible to a wide variety of diseases as well as provides insights into many body systems. Almost any part of the eye can give important clues to the diagnosis of systemic diseases. Signs of a systemic disease may be evident on the outer surface of the eye (eyelids, conjunctiva and cornea), middle of the eye and at the back of the eye (retina)."

Since 500 B.C., some researchers have believed that the physical condition of the fingernails and toenails can indicate various systemic diseases. Careful examination of the fingernails and toenails may provide clues to underlying systemic diseases , since some diseases have been found to cause disruptions in the nail growth process. The nail plate is the hard keratin cover of the nail. The nail plate is generated by the nail matrix located just under the cuticle. As the nail grows, the area closest to becoming exposed to the outside world (distal) produces the deeper layers of the nail plate, while the part of the nail matrix deeper inside the finger (proximal) makes the superficial layers. Any disruption in this growth process can lead to an alteration in the shape and texture.

For example, pitting looks like depressions in the hard part of the nail. Pitting is to be associated with psoriasis, affecting 10% - 50% of patients with that disorder. Pitting also may be caused by a variety of systemic diseases, including reactive arthritis and other connective tissue disorders, sarcoidosis, pemphigus, alopecia areata, and incontinentia pigmenti. Because pitting is caused by defective layering of the superficial nail plate by the proximal nail matrix, any localized dermatitis (e.g., atopic dermatitis or chemical dermatitis) that disrupts orderly growth in that area also can cause pitting.

White dot syndromes are inflammatory diseases characterized by the presence of white dots on the fundus, the interior surface of the eye. The majority of individuals affected with white dot syndromes are younger than fifty years of age. Some symptoms include blurred vision and visual field loss. There are many theories for the etiology of white dot syndromes including infectious, viral, genetics and autoimmune.

Classically recognized white dot syndromes include:

- Acute posterior multifocal placoid pigment epitheliopathy (APMPPE)

- Birdshot chorioretinopathy

- Multiple evanescent white dot syndrome (MEWDS)

- Acute zonal occult outer retinopathy (AZOOR)

- Multifocal choroiditis and panuveitis (MCP)

- Punctate inner choroiditis (PIC)

- Serpiginous choroiditis

Most commonly histiocytomas are found in young dogs and appear as a small, solitary, hairless lump, although Shar Peis may be predisposed to multiple histiocytomas. They are most commonly found on the head, neck, ears, and limbs, and are usually less than 2.5 cm in diameter. Ulceration of the mass is common. Diagnosis is made through cytology of the mass. Cytology reveals cells with clear to lightly basophilic cytoplasm and round or indented nuclei with fine chromatin and indistinct nucleoli.

Genodermatoses are inherited genetic skin conditions often grouped into three categories: chromosomal, single gene, and polygenetic.

- 18q deletion syndrome

- Acrodermatitis enteropathica

- Acrogeria (Gottron syndrome)

- Acrokeratosis verruciformis (acrokeratosis verruciformis of Hopf)

- Adams–Oliver syndrome

- Adducted thumbs syndrome

- Albright's hereditary osteodystrophy

- Angelman syndrome

- Apert syndrome (acrocephalosyndactyly)

- Arthrogryposis–renal dysfunction–cholestasis syndrome

- Ataxia telangiectasia (Louis–Bar syndrome)

- Atrichia with papular lesions (papular atrichia)

- Atrophodermia vermiculata (acne vermoulante, acne vermoulanti, atrophoderma reticulata symmetrica faciei, atrophoderma reticulatum, atrophoderma vermiculata, atrophoderma vermiculatum, atrophodermia reticulata symmetrica faciei, atrophodermia ulerythematosa, "atrophodermie vermiculée des joues avec kératoses folliculaires", folliculitis ulerythema reticulata, folliculitis ulerythematous reticulata, folliculitis ulerythemosa, honeycomb atrophy, ulerythema acneforme, ulerythema acneiforme)

- Autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy syndrome

- Bart syndrome

- Bazex–Dupré–Christol syndrome (Bazex syndrome, follicular atrophoderma and basal cell cacinomas)

- Beare–Stevenson cutis gyrata syndrome

- Bloom syndrome (Bloom–Torre–Machacek syndrome)

- Blue rubber bleb nevus syndrome

- Brittle hair–intellectual impairment–decreased fertility–short stature syndrome

- Cantú syndrome

- Cardio-facio-cutaneous syndrome (cardiofaciocutaneous syndrome)

- Cartilage–hair hypoplasia (McKusick type metaphyseal chondrodysplasia)

- Cerebral dysgenesis–neuropathy–ichthyosis–keratoderma syndrome

- Childhood tumor syndrome

- Chondrodysplasia punctata

- Cicatricial junctional epidermolysis bullosa

- Craniosynostosis–anal anomalies–porokeratosis syndrome

- Cockayne syndrome

- Colobomas of the eye–heart defects–ichthyosiform dermatosis–mental retardation–ear defects syndrome (CHIME syndrome, Zunich neuroectodermal syndrome, Zunich–Kaye syndrome)

- Congenital hemidysplasia with ichthyosiform erythroderma and limb defects syndrome (CHILD syndrome)

- Conradi–Hünermann syndrome (Conradi–Hünermann–Happle syndrome, Happle syndrome, X-linked dominant chondrodysplasia punctata)

- Costello syndrome

- Cronkhite–Canada syndrome

- Crouzon syndrome

- Cutis verticis gyrata

- Darier's disease (Darier–White disease, dyskeratosis follicularis, keratosis follicularis)

- DeSanctis–Cacchione syndrome

- Disseminated superficial actinic porokeratosis

- Disseminated superficial porokeratosis

- Dolichol kinase deficiency

- Dominant dystrophic epidermolysis bullosa

- Dyskeratosis congenita (Zinsser–Cole–Engman syndrome)

- Dystrophic epidermolysis bullosa

- Ectodermal dysplasia

- Ectodermal dysplasia with corkscrew hairs

- Ectrodactyly–ectodermal dysplasia–cleft syndrome (EEC syndrome, split hand–split foot–ectodermal dysplasia–cleft syndrome)

- Epidermolysis bullosa herpetiformis (Dowling–Meara epidermolysis bullosa simplex)

- Epidermolysis bullosa simplex

- Epidermolysis bullosa simplex of Ogna

- Epidermolysis bullosa simplex with mottled pigmentation

- Epidermolysis bullosa simplex with muscular dystrophy

- Epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma, bullous ichthyosiform erythroderma)

- Erythrokeratodermia with ataxia (Giroux–Barbeau syndrome)

- Familial benign chronic pemphigus (familial benign pemphigus, Hailey–Hailey disease)

- Fanconi syndrome (familial pancytopenia, familial panmyelophthisis)

- Fibrodysplasia ossificans progressiva

- Focal dermal hypoplasia (Goltz syndrome)

- Follicular atrophoderma

- Franceschetti–Klein syndrome (mandibulofacial dysostosis)

- Gardner's syndrome (familial colorectal polyposis)

- Gastrocutaneous syndrome

- Generalized atrophic benign epidermolysis bullosa

- Generalized epidermolysis bullosa simplex (Koebner variant of generalized epidermolysis bullosa simplex)

- Generalized trichoepithelioma

- Giant axonal neuropathy with curly hair

- Gingival fibromatosis with hypertrichosis

- Haber syndrome

- Hallerman–Streiff syndrome

- Harlequin-type ichthyosis (harlequin baby, harlequin fetus, harlequin ichthyosis, ichthyosis congenita, ichthyosis congenita gravior)

- Hay–Wells syndrome (AEC syndrome, ankyloblepharon filiforme adnatum–ectodermal dysplasia–cleft palate syndrome, ankyloblepharon–ectodermal defects–cleft lip and palate syndrome, ankyloblepharon–ectodermal dysplasia–clefting syndrome)

- Hereditary sclerosing poikiloderma

- Heterochromia iridum

- Holocarboxylase synthetase deficiency

- Hypohidrotic ectodermal dysplasia (anhidrotic ectodermal dysplasia, Christ–Siemens–Touraine syndrome)

- Hypotrichosis–acro-osteolysis–onychogryphosis–palmoplantar keratoderma–periodontitis syndrome

- Hypotrichosis–lymphedema–telangiectasia syndrome

- Ichthyosis–brittle hair–impaired intelligence–decreased fertility–short stature syndrome (IBIDS syndrome, sulfur-deficient brittle hair syndrome, Tay's syndrome, trichothiodystrophy, trichothiodystrophy with ichthyosis)

- Ichthyosis bullosa of Siemens (ichthyosis exfoliativa)

- Ichthyosis follicularis (ichthyosis follicularis with alopecia and photophobia syndrome)

- Ichthyosis linearis circumflexa

- Ichthyosis prematurity syndrome

- Ichthyosis vulgaris (autosomal dominant ichthyosis, ichthyosis simplex)

- Ichthyosis with confetti

- Neonatal ichthyosis–sclerosing cholangitis syndrome (ichthyosis–sclerosing cholangitis syndrome, NISCH syndrome)

- Incontinentia pigmenti achromians (hypomelanosis of Ito)

- Immune dysfunction–polyendocrinopathy–enteropathy–X-linked syndrome

- Jaffe–Campanacci syndrome

- Johanson–Blizzard syndrome

- Johnson–McMillin syndrome

- Joubert syndrome

- Junctional epidermolysis bullosa

- Junctional epidermolysis bullosa gravis (epidermolysis bullosa letalis, Herlitz disease, Herlitz epidermolysis bullosa, Herlitz syndrome, lethal junctional epidermolysis bullosa)

- Junctional epidermolysis bullosa with pyloric atresia

- Kabuki syndrome (Kabuki makeup syndrome, Niikawa–Kuroki syndrome)

- Keratolytic winter erythema (erythrokeratolysis hiemalis, Oudtshoorn disease, Oudtshoorn skin)

- Keratosis follicularis spinulosa decalvans (Siemens-1 syndrome)

- Keratosis linearis with ichthyosis congenital and sclerosing keratoderma syndrome

- Keratosis pilaris atrophicans faciei (folliculitis rubra, keratosis pilaris rubra atrophicans faciei, lichen pilare, "lichen pilaire ou xerodermie pilaire symmetrique de la face', ulerythema ophryogenes, "xerodermi pilaire symmetrique de la face")

- Keratosis pilaris

- Kindler syndrome (acrokeratotic poikiloderma, bullous acrokeratotic poikiloderma of Kindler and Weary, congenital poikiloderma with blisters and keratoses, congenital poikiloderma with bullae and progressive cutaneous atrophy, hereditary acrokeratotic poikiloderma, hyperkeratosis–hyperpigmentation syndrome, Weary–Kindler syndrome)

- Klinefelter syndrome

- Klippel–Feil syndrome

- Lamellar ichthyosis (collodion baby)

- Legius syndrome (neurofibromatosis type 1-like syndrome)

- Lelis syndrome

- Lenz–Majewski syndrome

- Leschke syndrome

- Lethal acantholytic epidermolysis bullosa

- Lhermitte–Duclos disease

- Linear and whorled nevoid hypermelanosis (linear nevoid hyperpigmentation, progressive cribriform and zosteriform hyperpigmentation, reticulate and zosteriform hyperpigmentation, reticulate hyperpigmentation of Iijima and Naito and Uyeno, zebra-like hyperpigmentation in whorls and streaks, zebra-line hyperpigmentation)

- Linear Darier disease (acantholytic dyskeratotic epidermal nevus)

- Linear porokeratosis

- Localized epidermolysis bullosa simplex (Weber–Cockayne syndrome, Weber–Cockayne variant of generalized epidermolysis bullosa simplex)

- Mandibuloacral dysplasia

- Marinesco–Sjögren syndrome

- McCune–Albright syndrome

- McCusick syndrome

- Metageria

- Microphthalmia–dermal aplasia–sclerocornea syndrome

- Mitis junctional epidermolysis bullosa (nonlethal junctional epidermolysis bullosa)

- Mitochondrial myopathy–encephalopathy–lactic acidosis–stroke syndrome

- Multiple lentigines syndrome (cardiocutaneous syndrome, Gorlin syndrome II, lentiginosis profusa syndrome, LEOPARD syndrome, progressive cardiomyopathic lentiginosis)

- Multiple pterygium syndrome

- Multiple sulfatase deficiency (Austin disease, mucosulfatidosis)

- Naegeli–Franceschetti–Jadassohn syndrome (chromatophore nevus of Naegeli)

- Netherton syndrome

- Neurofibromatosis type 1 (von Recklinghausen's disease)

- Neurofibromatosis type 3 (neurofibromatosis mixed type)

- Neurofibromatosis type 4 (neurofibromatosis variant type)

- Neutral lipid storage disease (Dorfman–Chanarin syndrome)

- Nonbullous congenital ichthyosiform erythroderma (congenital ichthyosiform erythroderma)

- Noonan syndrome

- Oculocerebrocutaneous syndrome (Delleman–Oorthuys syndrome)

- Oculodentodigital dysplasia

- Odonto–Tricho–Ungual–Digital–Palmar syndrome

- Oliver–McFarlane syndrome

- Orofaciodigital syndrome

- Pachydermoperiostosis (idiopathic hypertrophic osteoathorpathy, Touraine–Solente–Gole syndrome)

- Peeling skin syndrome (acral peeling skin syndrome, continual peeling skin syndrome, familial continual skin peeling, idiopathic deciduous skin, keratolysis exfoliativa congenita)

- Pfeiffer syndrome

- Photosensitivity–ichthyosis–brittle sulfur-deficient hair–impaired intelligence–decreased fertility–short stature syndrome

- Pityriasis rotunda (pityriasis circinata, tinea circinata)

- Plate-like osteoma cutis

- Plaque-type porokeratosis (classic porokeratosis, porokeratosis of Mibelli)

- Polyneuropathy–organomegaly–endocrinopathy–monoclonal gammopathy–skin changes syndrome (Crow–Fukase syndrome)

- Polyostotic fibrous dysplasia (Albright's disease)

- Popliteal pterygium syndrome

- Porokeratosis

- Porokeratosis palmaris et plantaris disseminata

- Prader–Willi syndrome

- Progeria (Hutchinson–Gilford progeria syndrome, Hutchinson–Gilford syndrome, progeria syndrome)

- Progressive osseous heteroplasia

- Progressive symmetric erythrokeratodermia (erythrokeratodermia progressiva symmetrica)

- Proteus syndrome

- Proteus-like syndrome

- Punctate porokeratosis

- Rapp–Hodgkin syndrome (Rapp–Hodgkin ectodermal dysplasia syndrome)

- Recessive dystrophic epidermolysis bullosa (Hallopeau–Siemens variant of epidermolysis bullosa, Hallopeau–Siemens disease)

- Refsum's disease (heredopathia atactica polyneuritiformis, phytanic acid storage disease)

- Relapsing linear acantholytic dermatosis

- Restrictive dermopathy

- Rhizomelic chondrodysplasia punctata (autosomal recessive chondrodysplasia punctata type 1, chondrodystrophia calcificans punctata, peroxisomal biogenesis disorder complementation group 11)

- Rombo syndrome

- Rothmund–Thomson syndrome (poikiloderma congenitale)

- Rud syndrome

- Say syndrome

- Scalp–ear–nipple syndrome (Finlay–Marks syndrome)

- Schindler disease (Kanzaki disease, alpha-N-acetylgalactosaminidase deficiency)

- Schinzel–Giedion syndrome

- Scleroatrophic syndrome of Huriez (Huriez syndrome, palmoplantar keratoderma with scleroatrophy, palmoplantar keratoderma with sclerodactyly, scleroatrophic and keratotic dermatosis of the limbs, sclerotylosis)

- Segmental neurofibromatosis

- Senter syndrome (Desmons' syndrome)

- Shabbir syndrome (laryngo–onycho–cutaneous syndrome)

- Silver–Russell syndrome

- Sjögren–Larsson syndrome

- Skin fragility syndrome (plakophilin 1 deficiency)

- Smith–Lemli–Opitz syndrome

- Sturge–Weber syndrome

- Supernumerary nipples–uropathies–Becker's nevus syndrome

- Terminal osseous dysplasia with pigmentary defects

- Tooth and nail syndrome (hypodontia with nail dysgenesis, Witkop syndrome)

- Townes–Brocks syndrome

- Transient bullous dermolysis of the newborn

- Treacher Collins syndrome (Treacher Collins–Franceschetti syndrome)

- Tricho–dento–osseous syndrome

- Tricho–rhino–phalangeal syndrome

- Tuberous sclerosis (Bourneville disease, epiloia)

- Turner syndrome

- Ulnar–mammary syndrome

- Van Der Woude syndrome

- Von Hippel–Lindau syndrome

- Watson syndrome

- Werner syndrome (adult progeria)

- Westerhof syndrome

- Whistling syndrome (craniocarpotarsal syndrome, distal arthrogryposis type 2, Freeman–Sheldon syndrome, Windmill–Vane–Hand syndrome)

- Wilson–Turner syndrome

- Wolf–Hirschhorn syndrome (4p- syndrome)

- X-linked ichthyosis (steroid sulfatase deficiency, X-linked recessive ichthyosis)

- X-linked recessive chondrodysplasia punctata

- Xeroderma pigmentosum (Cockayne syndrome complex)

- XXYY genotype

- Zimmermann–Laband syndrome

Some discrepancy exists as to whether acute zonal occult outer retinopathy (AZOOR) is actually considered a white dot syndrome. However, AZOOR may definitely be related to other diseases included in the white dot syndrome group. AZOOR occurs in young to middle age adults and may eventually progress to retinal cell death. Symptoms include acute visual field loss and photopsias. Suspected causes for AZOOR include autoimmune, viral, and fungal.

Periodic fever syndromes (also known as autoinflammatory diseases or autoinflammatory syndromes) are a set of disorders characterized by recurrent episodes of systemic and organ-specific inflammation. Unlike autoimmune disorders such as systemic lupus erythematosus, in which the disease is caused by abnormalities of the adaptive immune system, patients with autoinflammatory diseases do not produce autoantibodies or antigen-specific T or B cells. Instead, the autoinflammatory diseases are characterized by errors in the innate immune system.

The syndromes are diverse, but tend to cause episodes of fever, joint pains, skin rashes, abdominal pains and may lead to chronic complications such as amyloidosis.

Most autoinflammatory diseases are genetic and present during childhood. The most common genetic autoinflammatory syndrome is familial Mediterranean fever, which causes short episodes of fever, abdominal pain, serositis, lasting less than 72 hours. It is caused by mutations in the MEFV gene, which codes for the protein pyrin.

Pyrin is a protein normally present in the inflammasome. The mutated pyrin protein is thought to cause inappropriate activation of the inflammasome, leading to release of the pro-inflammatory cytokine IL-1β. Most other autoinflammatory diseases also cause disease by inappropriate release of IL-1β. Thus, IL-1β has become a common therapeutic target, and medications such as anakinra, rilonacept, and canakinumab have revolutionized the treatment of autoinflammatory diseases.

However, there are some autoinflammatory diseases that are not known to have a clear genetic cause. This includes PFAPA, which is the most common autoinflammatory disease seen in children, characterized by episodes of fever, aphthous stomatitis, pharyngitis, and cervical adenitis. Other autoinflammatory diseases that do not have clear genetic causes include adult-onset Still's disease, systemic-onset juvenile idiopathic arthritis, Schnitzler syndrome, and chronic recurrent multifocal osteomyelitis. It is likely that these diseases are multifactorial, with genes that make people susceptible to these diseases, but they require an additional environmental factor to trigger the disease.

Another example that shows that autoinflamatory conditions may not be genetic in origin is found in a report published in "Nature" which shows that diet is very important in the development of such diseases. The ingestion levels of highly saturated fats and cholesterol, (high fat diet, HFD) affects the microbiota composition of the gut. Changes in the microbiota induced by a HFD are protective against the susceptibility to develop osteomyelitis (autoimmune disease) as compared with the changes induced by a low-fat diet. The changes in the microbiome of individuals under HFD showed a reduction in "Prevotella" abundance and were accompanied by significantly reduced expression levels of pro-Interleukin-1β in distant neutrophils.

A rare disease is any disease that affects a small percentage of the population. In some parts of the world, an orphan disease is a rare disease whose rarity means there's a lack of a market large enough to gain support and resources for discovering treatments for it, except by the government granting economically advantageous conditions to creating and selling such treatments. Orphan drugs are ones so created or sold.

Most rare diseases are genetic, and thus are present throughout the person's entire life, even if symptoms do not immediately appear. Many rare diseases appear early in life, and about 30 percent of children with rare diseases will die before reaching their fifth birthday. With a single diagnosed patient only, ribose-5-phosphate isomerase deficiency is considered the rarest genetic disease.

No single cutoff number has been agreed upon for which a disease is considered rare. A disease may be considered rare in one part of the world, or in a particular group of people, but still be common in another.

Global Genes have estimated that more than 300 million people worldwide are living with one of the 7,000 diseases they define as "rare" in the United States.