Peripheral arthritis has been reported in 92% of cases of SAPHO as well.

In children, the SAPHO syndrome is most likely to affect the metaphysis of long bones in the legs (tibia, femur, fibula), followed by clavicles and spine.

SAPHO syndrome includes a variety of inflammatory bone disorders that may be associated with skin changes. These diseases share some clinical, radiologic, and pathologic characteristics.

An entity initially known as chronic recurrent multifocal osteomyelitis (CRMO) was first described in 1972. Subsequently, in 1978, several cases of CRMO were associated with blisters on the palms and soles (palmoplantar pustulosis). Since then, a number of associations between skin conditions and osteoarticular disorders have been reported under a variety of names, including sternocostoclavicular hyperostosis, pustulotic arthro-osteitis, and acne-associated spondyloarthropathy. The term SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) was coined in 1987 to represent this spectrum of inflammatory bone disorders that may or may not be associated with dermatologic pathology.

The definition is Synovitis Acne (commonly involving the face and upper back) Pustulosis Hyperostosis Osteitis

The disease has been reported to affect 3 per 1000 infants younger than 6 months in the United States. No predilection by race or sex has been established. Almost all cases occur by the age of 5 months. The familial form is inherited in an autosomal dominant fashion with variable penetrance. The familial form tends to have an earlier onset and is present at birth in 24% of cases, with an average age at onset of 6.8 weeks. The average age at onset for the sporadic form is 9–11 weeks.

Cortical hyperostosis is a potential side effect of long-term use of prostaglandins in neonates.

The age range of patients with OPLL is from 32 to 81 years (mean = 53), with a male predominance. Prevalence is higher in those of Japanese or Asian ancestry (2-3.5%) and rarer in other racial groups (0.16%). Schizophrenia patients in Japan may have as high as 20% incidence.

Infantile cortical hyperostosis is a self-limited condition, meaning that the disease resolves on its own without treatment, usually within 6–9 months. Long-term deformities of the involved bones, including bony fusions and limb-length inequalities, are possible but rare.

Most patients suffer from only mild symptoms. Symptoms typically last approximately 13 months. Of patients without myelopathy at initial presentation, only 29% of them will develop myelopathy within 30 years.

The exact cause is unknown. Mechanical factors, dietary and long term use of some antidepressants may be of significance. There is a correlation between these factors but not a cause or effect. The distinctive radiological feature of DISH is the continuous linear calcification along the antero-medial aspect of the thoracic spine. The disease is usually found in people in their 60s and above, and is extremely rare in people in their 40s and 30s. The disease can spread to any joint of the body, affecting the neck, shoulders, ribs, hips, pelvis, knees, ankles, and hands. The disease is not fatal, however some associated complications can lead to death. Complications include paralysis, dysphagia (the inability to swallow), and pulmonary infections. Although DISH manifests in a similar manner to ankylosing spondylitis, these two are totally separate diseases. Ankylosing spondylitis is a genetic disease with identifiable marks, and affects organs. DISH has no indication of a genetic link, and does not affect organs other than the lungs, which is only indirect due to the fusion of the rib cage.

Long term treatment of acne with vitamin derived retinoids, such as etretinate and acitretin, have been associated with "extraspinal" hyperostosis.

Treatment should be sought immediately in order to avoid hospitalization. If not treated, hospitalization for an extended period of time (usually two weeks) is likely. During hospitalization, the patient is tested for signs of system degradation, especially of the skeletal structure and the digestive tract. By this time open sores will develop on the upper torso. Some will be the size of dimes, others will be large enough to stick a couple fingers into. They will crust up, causing cohesion to any fabric the sores touch, which is extremely painful to remove. It is recommended to sleep on one's sides until the cystic condition subsides, in order to avoid any uncomfortable situations. Debridement and steroid therapy is preferred over antibiotics. Recurrent AF is extremely rare. Bone lesions typically resolve with treatment, but residual radiographic changes, such as sclerosis and hyperostosis, may remain. Scarring and fibrosis may result from this acute inflammatory process.

The disease activates at the height of puberty, usually at around 13 years of age. Acne fulminans predominantly affects young males aged 13 to 22 years with a history of acne.

Craniomandibular osteopathy, also known as lion's jaw, is a developmental disease in dogs causing extensive bony changes in the mandible and skull. In this disease, a cyclical resorption of normal bone and replacement by immature bone occurs along the inner and outer surfaces of the affected bones. It usually occurs between the ages of 3 and 8 months. Breeds most commonly affected include the West Highland White Terrier, Scottish Terrier, Cairn Terrier, and Boston Terrier. It is rare in large-breed dogs, but it has been reported. Symptoms include firm swelling of the jaw, drooling, pain, and difficulty eating.

It is an inherited disease, especially in Westies, in which it has been recognized as an autosomal recessive trait. Canine distemper has also been indicated as a possible cause, as has "E. coli" infection, which could be why it is seen occasionally in large-breed dogs. Growth of lesions will usually stop around the age of one year, and possibly regress. This timing coincides with the normal completion of endochondral bone growth and ossification. If the disease is extensive, especially around the tympanic bulla (middle ear), then the prognosis is guarded.

A similar disease seen in young Bullmastiffs is known as calvarial hyperostotic syndrome. It is also similar to human infantile cortical hyperostosis. It is characterized by irregular, progressive bony proliferation and thickening of the cortical bone of the calvaria, which is part of the skull. Asymmetry of the lesions may occur, which makes it different from craniomandibular osteopathy. Symptoms include painful swelling of the skull, fever, and lymph node swelling. In most cases it is self-limiting.

Acne fulminans (also known as "acute febrile ulcerative acne") is a severe form of the skin disease, acne, which can occur after unsuccessful treatment for another form of acne, acne conglobata. The condition is thought to be an immunologically induced disease in which elevated level of testosterone causes a rise in sebum and population of "Propionibacterium acnes" bacteria. The increase in the amount of "P acnes" or related antigens may trigger the immunologic reaction in some individuals and lead to an occurrence of acne fulminans. In addition to testosterone, isotretinoin may also precipitate acne fulminans, possibly related to highly increased levels of "P acnes antigens" in the patient's immune system. Acne fulminans is a rare disease. Over the past several years, fewer cases of this disease have occurred, possibly because of earlier and better treatment of acne. Approximately 100 patients with acne fulminans have been described.

Porotic hyperostosis, also known as osteoporosis symmetrica, cribra crani, hyperostosis spongiosa, and symmetrical osteoporosis is a pathological condition that affects bones of the cranial vault, and is characterized by localized areas of spongy or porous bone tissue. The diploë, or spongy tissue within the bones of the cranium, swells and the tissue of the outer surface becomes thinner and more porous in appearance.

This condition was widely accepted as a result of anemia, which is typically due to an iron deficient diet, but several lines of evidence suggest that the accelerated loss and compensatory over-production of red blood cells seen in hemolytic and megaloblastic anemia are the most likely proximate causes of porotic hyperostosis.

In anthropology, the presence of the condition has been considered evidence that a past population suffered chronic or episodic malnutrition. Anthropologists examine bones of past populations to learn about their lifestyles. A sub-discipline known as paleonutrition has focused on the presence of porotic hyperostosis, among other nutritional disorders. A high incidence of the disease indicates the population adapted poorly to its environment or was under nutritional stress. A low level of iron in the blood is also a defense against pathogens, so a high incidence of the disease in a population could also indicate an attempt to fight off an infectious disease. From this perspective, porotic hyperostosis could be viewed as a biological attempt to adapt to the environment, rather than an indicator of malnutrition.

Diffuse idiopathic skeletal hyperostosis (DISH) is a non-inflammatory spondyloarthropathy which predominantly affects the spine. It is characterized by ankylosis and enthesopathy (ossification of the ligaments and entheses). It most commonly affects the thoracic and thoraco-lumbar spine, but involvement is variable and can include the entire spine.

In racquet nails (also known as brachyonychia, nail en raquette, and racquet thumb), the nail plate is flattened, the end of the thumb is widened and flattened, and the distal phalanx is abnormally short. In racquet nails, the width of the nail bed and nail plate is greater than their length. The condition is painless and asymptomatic.

Racquet nails usually occur on one or both thumbs, but may appear on all fingers and toes. It may be genetic, inherited as an autosomal-dominant trait, or acquired. Genetic disorders associated with racquet nail include Larsen syndrome, Brooke–Spiegler syndrome, Rubinstein–Taybi syndrome, Hajdu–Cheney syndrome, cartilage–hair hypoplasia, pycnodysostosis, acrodysostosis, and brachydactylia.

Acquired racquet nail is associated with acroosteolysis and psoriatic arthropathy. Acquired racquet nail may also be diagnostic of bone resorption in hyperparathyroidism.

Racquet nail often presents with other nail conditions such as onycholysis, koilonychia, pachyonychia, Muehrcke's lines, leuconychia, and half-and-half nails. Cosmetic surgery can be used to improve the appearance of the nails.

Worth syndrome is caused by a mutation in the LRP5 gene, located on human chromosome 11q13.4. The disorder is inherited in an autosomal dominant fashion. This indicates that the defective gene responsible for a disorder is located on an autosome (chromosome 11 is an autosome), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.

Normally, asymptomatic cases are not treated. Non-steroidal anti inflammatory drugs and surgery are two typical options for the rest.

There are a number of acquired causes of local gigantism. A body part can attain bigger size from causes as common as the following:

- inflammation, due to trauma or infection

- tumors like osteoid osteoma, melorheostosis, and lipofibromatous hamartoma

- Arteriovenous malformations occurring on a limb, before the closure of epiphyses in long bones

- Elephantiasis, which is quite common in south-east asia due to prevalence of filariasis.

- Still's disease

- amyloidosis

- acromegaly

Congenital causes include:

- Klippel Trenaunay Weber syndrome

- Maffucci syndrome

- macrodystrophia lipomatosa

- neurofibromatosis,

- lipoatrophic diabetes.

- Proteus syndrome, which by one theory accounts for the deformities of the Elephant Man

Worth syndrome, also known as benign form of Worth hyperostosis corticalis generalisata with torus platinus, autosomal dominant osteosclerosis, autosomal dominant endosteal hyperostosis or Worth disease, is a rare autosomal dominant congenital disorder that is caused by a mutation in the LRP5 gene. It is characterized by increased bone density and benign bony structures on the palate.

Hyperostosis is an excessive growth of bone. It may lead to exostosis. It occurs in many musculoskeletal disorders.

Phakomatoses are inconsistently defined, and there is a lack of consensus about what conditions are included in this category.

Conditions included are:

- Ataxia telangiectasia

- Incontinentia pigmenti

- Neurofibromatosis

- Nevoid basal cell carcinoma syndrome

- Sturge-Weber syndrome

- Tuberous sclerosis

- Wyburn-Mason syndrome (Bonnet–Dechaume–Blanc syndrome)

- von Hippel-Lindau disease

The only effective line of treatment for malignant infantile osteopetrosis is hematopoietic stem cell transplantation. It has been shown to provide long-term disease-free periods for a significant percentage of those treated; can impact both hematologic and skeletal abnormalities; and has been used successfully to reverse the associated skeletal abnormalities.

Radiographs of at least one case with malignant infantile osteopetrosis have demonstrated bone remodeling and recanalization of medullar canals following hematopoietic stem cell transplantation. This favorable radiographic response could be expected within one year following the procedure - nevertheless, primary graft failure can prove fatal.

Estimating the mortality rate based on the available literature is difficult. Several case reports have revealed an association between acquired partial lipodystrophy and other diseases.

Nephropathy, in the form of membranoproliferative glomerulonephritis, occurs in about 20% of patients. Usually, patients do not have clinically evident renal disease or abnormalities in renal function until they have had the disease for 8 or more years. Membranoproliferative glomerulonephritis usually presents with asymptomatic proteinuria or hematuria.

The disease may gradually progress. About 40-50% of patients develop end-stage renal disease over the course of 10 years. This condition is responsible for most recurrent hospital admissions in patients with acquired partial lipodystrophy. Rapid progression of renal disease in a pregnant patient was reported. Recurrent disease in transplanted kidneys is common, although there have been reports of successful transplantations.

Associated autoimmune diseases (e.g., systemic lupus erythematosus, thyroiditis) contribute significantly to increased morbidity in these patients compared with the general population. Although uncommon, insulin resistance increases cardiovascular risk. Susceptibility to bacterial infections probably results from a C3 deficiency (due to complement activation and consumption of C3). Low C3 levels may impair complement-mediated phagocytosis and bacterial killing.

Around 250 cases have been reported since the recognition of this syndrome. It is a rare syndrome with no known prevalence, although it is more common than the generalized form of acquired lipodystrophy (Lawrence syndrome).

- Race: No clear relationship exists between incidence and race in this syndrome; however, most reported patients have been of European descent.

- Age: The median age of onset of lipodystrophy has been reported to be around seven years; however, onset occurring as late as the fourth or fifth decade of life also has been reported. The median age at presentation has been about 25 years, and women have been found to present later than men (age 28 for women, age 18 for men).

- Sex: Analysis of the pooled data revealed female patients were affected about four times more often than males.

Evidence for bone spurs found in the fossil record is studied by paleopathologists, specialists in ancient disease and injury. Bone spurs have been reported in dinosaur fossils from several species, including "Allosaurus fragilis", "Neovenator salerii", and "Tyrannosaurus rex".

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.