Peeling skin syndrome (also known as "Acral peeling skin syndrome," "Continual peeling skin syndrome," "Familial continual skin peeling," "Idiopathic deciduous skin," and "Keratolysis exfoliativa congenita") is an autosomal recessive disorder characterized by lifelong peeling of the stratum corneum, and may be associated with pruritus, short stature, and easily removed anagen hair.

The acral form can be associated with "TGM5".

PVA usually has an underlying cause, attributed to existing skin diseases and disorders associated with a cutaneous lymphoma or inflammation. Mycosis fungoides is the common lymphoma believed to cause PVA, although it may be considered a precursor when the lymphoma is (hidden) and undiagnosed. Large plaque parapsoriasis is another common causes of PVA. Less common causes include autoimmune-related connective tissue diseases such as lupus, dermatomyositis and scleroderma. Dermatoses and those that are genetically inspired, called genodermatoses, may also be an underlying cause of PVA. Among them, xeroderma pigmentosum and Rothmund-Thomson syndrome (poikiloderma congenita) are thought to be the most prominent. Ingestion of substances containing arsenic, such as arsphenamine, has also been suggested as a least common cause. PVA can also be idiopathic (of unknown cause), as seen in a small number of cases.

AC is caused by chronic and excessive exposure to ultraviolet radiation in sunlight.

Risk factors include:

- Outdoor lifestyle: e.g. farmers, sailors, fishermen, windsurfers, mountaineers, golfers, etc. This has given rise to synonyms for this condition such as "sailor's lip" and "farmer's lip". The prevalence in agricultural workers in a semi-arid region of Brazil is reported to be 16.7%.

- Light skin complexion: the condition typically affects individuals with lighter skin tones, particularly Caucasians living in tropical regions. In one report, 96% of persons with AC had phenotype II according to the Fitzpatrick scale.

- Age: AC typically affects older individuals, and rarely those under the age of 45.

- Gender: the condition affects males more commonly than females. Sometimes this ratio is reported as high as 10:1.

Additional factors may also play a role, including tobacco use, lip irritation, poor oral hygiene, and ill-fitting dentures.

The appearance is often described as a shiny film looking like a layer of vaseline. The eyelids and mouth may have the appearance of being forced open due to the tightness of the skin. There can be associated eversion of the eyelids (ectropion).

Collodion baby can have severe medical consequences, mainly because the baby can lose heat and fluid through the abnormal skin. This can lead to hypothermia and dehydration. Strategies to prevent these problems are the use of emollients or nursing the baby in a humidified . There is also an increased risk of skin infection and mechanical compression, leading to problems like limb ischemia. There is also a risk of intoxication by cutaneous absorption of topical products, for example salicylate intoxication (similar to aspirin overdose) due to keratolytics.

The condition is not thought to be painful or in itself distressing to the child. Nursing usually takes place in a neonatal intensive care unit, and good intensive care seems to have improved the prognosis markedly. The collodion membrane should peel off or "shed" 2 to 4 weeks after birth, revealing the underlying skin disorder.

The condition can resemble but is different from harlequin type ichthyosis.

Most patients with hyper IgE syndrome are treated with long-term antibiotic therapy to prevent staphylococcal infections. Good skin care is also important in patients with hyper IgE syndrome. High-dose intravenous gamma-globulin has also been suggested for the treatment of severe eczema in patients with HIES and atopic dermatitis.

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.

To prevent AC from developing, protective measures could be undertaken such as avoiding mid-day sun, or use of a broad-brimmed hat, lip balm with anti UVA and UVB ingredients (e.g. para-aminobenzoic acid), or sun blocking agents (e.g. zinc oxide, titanium oxide) prior to sun exposure.

Lamellar ichthyosis, also known as ichthyosis lamellaris and nonbullous congenital ichthyosis, is a rare inherited skin disorder, affecting around 1 in 600,000 people.

Acrogeria is extremely rare, with only about 40 cases having been reported in the medical literature, since 1941.

Beare–Stevenson cutis gyrata syndrome is so rare that a reliable incidence cannot be established as of yet; fewer than 20 patients with the condition have been reported.

Skin tags are thought to occur from skin rubbing up against skin, since they are so often found in skin creases and folds. Studies have shown existence of low-risk HPV 6 and 11 in skin tags, hinting at a possible role in its pathogenesis. Acrochorda have been reported to have a prevalence of 46% in the general population. A causal genetic component is thought to exist. They also are more common in women than in men. Rarely, they can be associated with the Birt–Hogg–Dubé syndrome, acromegaly, and polycystic ovary syndrome.

Skin tags may serve as a marker for those people whose carbohydrate metabolism is impaired and for those who may be at risk for diabetes mellitus type 2, although such a link has not been shown. Elevated blood sugar and insulin increase the incidence of skin tags through an unknown mechanism.

A number of conditions may cause the appearance of livedo reticularis:

- Cutis marmorata telangiectatica congenita, a rare congenital condition

- Sneddon syndrome – association of livedoid vasculitis and systemic vascular disorders, such as strokes, due to underlying genetic cause

- Idiopathic livedo reticularis – the most common form of livedo reticularis, completely benign condition of unknown cause affecting mostly young women during the winter: It is a lacy purple appearance of skin in extremities due to sluggish venous blood flow. It may be mild, but ulceration may occur later in the summer.

- Secondary livedo reticularis:

- Vasculitis autoimmune conditions:

- Livedoid vasculitis – with painful ulceration occurring in the lower legs

- Polyarteritis nodosa

- Systemic lupus erythematosus

- Dermatomyositis

- Rheumatoid arthritis

- Lymphoma

- Pancreatitis

- Chronic pancreatitis

- Tuberculosis

- Drug-related:

- Adderall (side effect)

- Amantadine (side effect)

- Bromocriptine (side effect)

- Beta IFN treatment, "i.e." in multiple sclerosis

- Livedo reticularis associated with rasagiline

- Methylphenidate and dextroamphetamine-induced peripheral vasculopathy

- Gefitinib

- Obstruction of capillaries:

- Cryoglobulinaemia – proteins in the blood that clump together in cold conditions

- Antiphospholipid syndrome due to small blood clots

- Hypercalcaemia (raised blood calcium levels which may be deposited in the capillaries)

- Haematological disorders of polycythaemia rubra vera or thrombocytosis (excessive red cells or platelets)

- Infections (syphilis, tuberculosis, Lyme disease)

- Associated with acute renal failure due to cholesterol emboli status after cardiac catheterization

- Arteriosclerosis (cholesterol emboli) and homocystinuria (due to Chromosome 21 autosomal recessive Cystathionine beta synthase deficiency)

- Intra-arterial injection (especially in drug addicts)

- Ehlers-Danlos syndrome – connective tissue disorder, often with many secondary conditions, may be present in all types

- Pheochromocytoma

- Livedoid vasculopathy and its association with factor V Leiden mutation

- FILS syndrome (polymerase ε1 mutation in a human syndrome with facial dysmorphism, immunodeficiency, livedo, and short stature)

- Primary hyperoxaluria, oxalosis (oxalate vasculopathy)

- Cytomegalovirus infection (very rare clinical form, presenting with persistent fever and livedo reticularis on the extremities and cutaneous necrotizing vasculitis of the toes)

- Generalized livedo reticularis induced by silicone implants for soft tissue augmentation

- As a rare skin finding in children with Down syndrome

- Idiopathic livedo reticularis with polyclonal IgM hypergammopathy

- CO angiography (rare, reported case)

- A less common skin lesion of Churg-Strauss syndrome

- Erythema nodosum-like cutaneous lesions of sarcoidosis showing livedoid changes in a patient with sarcoidosis and Sjögren's syndrome

- Livedo vasculopathy associated with IgM antiphosphatidylserine-prothrombin complex antibody

- Livedo vasculopathy associated with plasminogen activator inhibitor-1 promoter homozygosity and prothrombin G20210A heterozygosity

- As a first sign of metastatic breast carcinoma (very rare)

- Livedo reticularis associated with renal cell carcinoma (rare)

- Buerger's disease (as an initial symptom)

- As a rare manifestation of Graves hyperthyroidism

- Associated with pernicious anaemia

- Moyamoya disease (a rare, chronic cerebrovascular occlusive disease of unknown cause, characterized by progressive stenosis of the arteries of the circle of Willis leading to an abnormal capillary network and resultant ischemic strokes or cerebral hemorrhages)

- Associated with the use of a midline catheter

- Familial primary cryofibrinogenemia.

Frequencies of this disease are the greatest in Norway with a few Finnish cases have also having been noted to date. Some cases have been found in other ethnicities such as in people of Indian or Japanese descent as well as a north Italian family. These cases are scattered and there are potentially more under reported cases as this disease is often under diagnosed for other cutaneous diseases. It is most prevalent in a defined region in the middle of Norway and Sweden with a heterozygote carrier frequency of 1 in 50.

Microphthalmia–dermal aplasia–sclerocornea syndrome (also known as "MIDAS syndrome") is a condition characterized by linear skin lesions.

MLS is a rare X-linked dominant male-lethal disease characterized by unilateral or bilateral microphthalmia and linear skin defects in affected females, and in utero lethality for affected males. It can be associated with "HCCS", but mutations in the MCCS gene cause Microphthalmia with Linear Skin Defects Syndrome.

Other than identifying and treating any underlying conditions in secondary livedo, idiopathic livedo reticularis may improve with warming the area.

There are no life-threatening complications after the perinatal period (around the time of birth) and the skin conditions persist but to a lesser degree of severity. Individuals have a favourable prognosis as symptoms can be managed and past the infancy stage are not life-threatening. The red skin edema improves after a three-week period but the ichthyosis scaling persists. Asthma has been recorded in some cases later on in the individual's life and sign of atopic dermatitis persist, follicular hyperkeratosis and small amounts of scaling at the scalp that goes on into adulthood but otherwise the individual continues a healthy life.

The decision to observe or treat a nevus may depend on a number of factors, including cosmetic concerns, irritative symptoms (e.g., pruritus), ulceration, infection, and concern for potential malignancy.

The cause of acrogeria is still not well determined. This disorder is thought to be inherited as an autosomal recessive genetic trait. However, the mode of genetic inheritance is not accurately known. It has been considered autosomal dominant and autosomal recessive, though most reported cases own a positive family background.

Mutations in the COL3A1 gene, located at chromosome 2q31–q32, have been reported in varied phenotypes, including acrogeria and vascular rupture in Ehlers-Danlos' syndrome (more especially type IV).

In the fibroblast culture, a reduction of RNA messenger cells in collagen types I and II was found, as well as reduced life expectancy of the fibroblasts most prematurely showing morphological alterations typical of aging.

This seems perfectly compatible with the patients' aged phenotype.

Poikiloderma vasculare atrophicans (PVA), sometimes referred to as parapsoriasis variegata or parapsoriasis lichenoides is a cutaneous condition (skin disease) characterized by hypo- or hyperpigmentation (diminished or heightened skin pigmentation, respectively), telangiectasia and skin . Other names for the condition include prereticulotic poikiloderma and atrophic parapsoriasis. The condition was first described by pioneer American pediatrician Abraham Jacobi in 1906. PVA causes areas of affected skin to appear speckled red and inflamed, yellowish and/or brown, gray or grayish-black, with scaling and a thinness that may be described as "cigarette paper". On the surface of the skin, these areas may range in size from small patches, to plaques (larger, raised areas), to neoplasms (spreading, tumor-like growths on the skin).

Mycosis fungoides, a type of skin lymphoma, may be a cause of PVA. The condition may also be caused by, associated with or accompany any of the following conditions or disorders: other skin lymphomas, dermatomyositis, lupus erythematosus, Rothmund-Thompson syndrome, Kindler syndrome, dyskeratosis congenita, and chronic radiodermatitis. Rare causes include arsenic ingestion, and the condition can also be idiopathic.

PVA may be considered a rare variant of cutaneous T-cell lymphoma, a non-Hodgkin's form of lymphoma affecting the skin. It may also be included among a number of similar conditions that are considered as precursors to mycosis fungoides. PVA is believed to be a syndrome closely associated with large-plaque parapsoriasis and its cohort retiform parapsoriasis; including PVA, all three conditions fit within an updated view of the once ambiguous classification scheme known as parapsoriasis.

NBCCS has an incidence of 1 in 50,000 to 150,000 with higher incidence in Australia. One aspect of NBCCS is that basal-cell carcinomas will occur on areas of the body which are not generally exposed to sunlight, such as the palms and soles of the feet and lesions may develop at the base of palmar and plantar pits.

One of the prime features of NBCCS is development of multiple BCCs at an early age, often in the teen years. Each person who has this syndrome is affected to a different degree, some having many more characteristics of the condition than others.

In most cases, cutis laxa is inherited. Autosomal dominant, autosomal recessive, and X-linked recessive forms have been described, but acquired forms also occur.

Cutis laxa is associated with deficient or absent elastin fibers in the extracellular matrix. Various mutations in genes have been identified.

Cutis laxa may be caused by mutations in the genes: "ELN", "ATP6V0A2",

ATP7A, "FBLN4", "FBLN5", and "PYCR1". A related neurocutaneous syndrome may be caused by mutations in the gene "ALDH18A1" ("P5CS").

A lentigo () (plural lentigines, ) is a small pigmented spot on the skin with a clearly defined edge, surrounded by normal-appearing skin. It is a harmless (benign) hyperplasia of melanocytes which is linear in its spread. This means the hyperplasia of melanocytes is restricted to the cell layer directly above the basement membrane of the epidermis where melanocytes normally reside. This is in contrast to the "nests" of multi-layer melanocytes found in moles (melanocytic nevi). Because of this characteristic feature, the adjective "lentiginous" is used to describe other skin lesions that similarly proliferate linearly within the basal cell layer.

Lentigines are distinguished from freckles (ephelis) based on the proliferation of melanocytes. Freckles have a relatively normal number of melanocytes but an increased "amount" of melanin. A lentigo has an increased "number" of melanocytes. Freckles will increase in number and darkness with sunlight exposure, whereas lentigines will stay stable in their color regardless of sunlight exposure.

Lentigines by themselves are benign, however one might desire the removal or treatment of some of them for cosmetic purposes. In this case they can be removed surgically, or lightened with the use of topical depigmentation agents. Some common depigmentation agents such as azelaic acid and kojic acid seem to be inefficient in this case, however other agents might work well (4% hydroquinone, 5% topical cysteamine, 10% topical ascorbic acid).

Conditions characterized by lentigines include:

- Lentigo simplex

- Solar lentigo (Liver spots)

- PUVA lentigines

- Ink spot lentigo

- LEOPARD syndrome

- Mucosal lentigines

- Multiple lentigines syndrome

- Moynahan syndrome

- Generalized lentiginosis

- Centrofacial lentiginosis

- Carney complex

- Inherited patterned lentiginosis in black persons

- Partial unilateral lentiginosis

- Peutz-Jeghers syndrome

- Lentigo maligna

- Lentigo maligna melanoma

- Acral lentiginous melanoma

This condition has been linked to mutations in the ribosomal GTPase BMS1 gene.

Sack–Barabas syndrome is rare and has an estimated prevalence of 1 in 100,000 to 200,000.

The initial clinical manifestation of vascular problems in patients with SBS is early, about 25% have their first symptoms at age 20 and more than 80% of patients have had at least one complication by the age of 40.

The median survival for one study of SBS patients was only 48 years.

Cutis laxa (also known as chalazoderma, dermatochalasia, dermatolysis, dermatomegaly, generalized elastolysis, generalized elastorrhexis, or pachydermatocele) is a group of rare connective tissue disorders in which the skin becomes inelastic and hangs loosely in folds.