Hereditary multiple exostoses (HME), also called hereditary multiple osteochondromas (HMO), is a condition that is estimated to affect 1 in 50,000 individuals. Multiple benign or noncancerous bone tumors develop in the affected individuals. The number and location vary among affected patients. Most people seem unaffected at birth; however, by the age of 12 years, they develop multiple exostoses.

Surgical excision is performed when exostoses lead to growth disturbances or lead to disability. Knee osteotomies are associated with high incidence of peroneal nerve paralysis.

Surgery, physical therapy and pain management are currently the only options available to HME patients, but success varies from patient to patient and many struggle with pain, fatigue and mobility problems throughout their lives.

It is not uncommon for HME patients to undergo numerous surgical procedures throughout their lives to remove painful or deforming exostoses, correct limb length discrepancies or improve range of motion. Usually the treatment can be problematic. The osteochondromas can return in the same places and may be more painful.

Evidence for exostosis found in the fossil record is studied by paleopathologists, specialists in ancient disease and injury. Exostosis has been reported in dinosaur fossils from several species, including "Acrocanthosaurus atokensis", "Albertosaurus sarcophagus", "Allosaurus fragilis", "Gorgosaurus libratus", and "Poekilopleuron bucklandii".

Hereditary multiple exostoses (HME or MHE), also known as diaphyseal aclasis, is a rare medical condition in which multiple bony spurs or lumps (also known as exostoses, or osteochondromas) develop on the bones of a child. HME is synonymous with multiple hereditary exostoses and multiple osteochondromatosis, which is the preferred term used by the World Health Organization.

Osteogenesis imperfecta is a rare condition in which bones break easily. There are multiple genetic mutations in different genes for collagen that may result in this condition. It can be treated with some drugs to promote bone growth, by surgically implanting metal rods in long bones to strengthen them, and through physical therapy and medical devices to improve mobility.

Osteochondromatosis is a condition involving a proliferation of osteochondromas.

Types include:

- Hereditary multiple exostoses

- Synovial osteochondromatosis

Osteochondrodysplasia or skeletal dysplasia is a general term for a disorder of the development (dysplasia) of bone ("osteo") and cartilage ("chondro").

Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia.

Osteochondromas or osteocartilaginous exostoses are the most common benign tumors of the bones.

The tumors take the form of cartilage-capped bony projections or outgrowth on the surface of bones (exostoses). It is characterized as a type of overgrowth that can occur in any bone where cartilage forms bone. Tumors most commonly affect long bones in the leg, pelvis, or scapula (shoulder blade). Development of osteochondromas take place during skeletal growth between the ages of 13 and 15 and ceases when the growth plate fuses at puberty. They arise within the first three decades of life affecting children and adolescents.

Osteochondromas occur in 3% of the general population and represent 35% of all benign tumors and 8% of all bone tumors. Majority of these tumors are solitary non-hereditary lesions and approximately 15% of osteochondromas occur as hereditary multiple osteochondromas (HMOs). They can occur as a solitary lesion (solitary osteochondroma) or multiple lesions within the context of the same bone (Multiple Osteochondroma). Osteochondromas do not result from injury and the exact cause remains unknown. Recent research has indicated that multiple osteochondromas is an autosomal dominant inherited disease. Germ line Mutations in "EXT1" and "EXT2" genes located on chromosomes 8 and 11 have been associated with the cause of the disease.

The treatment choice for osteochondroma is surgical removal of solitary lesion or partial excision of the outgrowth, when symptoms cause motion limitations or nerve and blood vessel impingements.

Osteochondromas are benign lesions and do not affect life expectancy. Complete excision of osteochondroma is curative and the reoccurrences take place when the removal of tumor is incomplete. Multiple reoccurrences in a well-excised lesion indicate that it may be malignant. The risk of malignant transformation takes place in 1–5% of individuals. If any symptoms of cancerous tumor takes place, then the patient should be evaluated by a bone specialist. No treatment is necessary for Solitary osteochondromas that are asymptomatic. Treatments for solitary osteochondroma are careful observation over time and taking regular x-rays to monitor any changes in the tumor. If the lesion is causing pain with activity, nerve or vessel impingement, or if the bone growth has fully matured and the presence of a large cartilage cap is prominent, then it is advised that the tumor be surgically removed.

Osteochondromas have a low rate of malignancy (<1%) and resection of the tumor is suggested if symptoms such as pain, limitation of movement, or impingement on nerves or vessels occur. Resection of the tumor also takes place when the tumor increases in size and progresses towards malignancy. During surgical resection, the entire lesion along with the cartilaginous cap should be removed to minimize any chances of reoccurrences. Surgical treatment becomes the sole treatment of choice if common complications such as fractures, symptoms of peripheral nerves such as paresthesia, paraplegia, peroneal neuropathy, and upper limb neuropathy take place. A prophylactic resection is suggested if the lesion lies next to a vessel.

Depending on the size and location of the tumor, the time it takes to return to normal daily activities varies between individuals. Limitation on some activities is advised if pain or discomfort persists after surgical excision.

Biophosphonates are drugs that are used to prevent bone mass loss and are often used to treat osteolytic lesions. Zoledronic acid (Reclast) is a specific drug given to cancer patients to prevent the worsening of bone lesions and has been reported to have anti-tumor effects as well. Zoledronic acid has been clinically tested in conjunction with calcium and vitamin D to encourage bone health. Denosumab, a monoclonal antibody treatment RANKl inhibitor that targets the osteocyte apoptosis regualtory RANKL gene, is also prescribed to prevent bone metastases and bone lesions. Most biophosphonates are co-prescribed with disease-specific treatments, such as chemotherapy or radiation for cancer patients.

Bone lesions in multiple myeloma patients may be treated with low-dose radiation therapy in order to reduce pain and other symptoms. Used in combination with immunochemotherapy, radiation therapy can be used to treat certain cancers when aimed at areas of bone lesion and softened bone.

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

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".

Generally buccal exostoses require no treatment. However, they may be easily traumatized causing ulceration, or may contribute to periodontal disease if they become too large, or can interfere with wearing a denture (false teeth). If they are creating problems, they are generally removed with a simple surgical procedure under local anesthetic.

Surgical excision is common and is a very effective mode of treatment.

Management entails careful examination and monitoring for malignant degenerations. Surgical interventions can correct or minimize deformities.

Treatment is usually supportive treatment, that is, treatment to reduce any symptoms rather than to cure the condition.

- Enucleation of the odontogenic cysts can help, but new lesions, infections and jaw deformity are usually a result.

- The severity of the basal-cell carcinoma determines the prognosis for most patients. BCCs rarely cause gross disfigurement, disability or death .

- Genetic counseling

Autosomal recessive multiple epiphyseal dysplasia (ARMED), also called epiphyseal dysplasia, multiple, 4 (EDM4), multiple epiphyseal dysplasia with clubfoot or –with bilayered patellae, is an autosomal recessive congenital disorder affecting cartilage and bone development. The disorder has relatively mild signs and symptoms, including joint pain, scoliosis, and malformations of the hands, feet, and knees.

Some affected individuals are born with an inward- and downward-turning foot (a clubfoot). An abnormality of the kneecap called a double-layered patella is also relatively common. Although some people with recessive multiple epiphyseal dysplasia have short stature as adults, most are of normal height. The incidence is unknown as many cases are not diagnosed due to mild symptoms.

A buccal exostosis (also termed alveolar exostosis), is an exostosis (bone prominence) on the buccal surface (cheek side) of the alveolar ridge of the maxilla or mandible. Some consider them a variation of normal anatomy rather than a disease.

Maffucci syndrome is a sporadic disease characterized by the presence of multiple enchondromas associated with multiple hemangiomas. Also lymphangiomas may be apparent.

Multiple familial trichoepithelioma (also known as Brooke–Spiegler syndrome and epithelioma adenoides cysticum) is a cutaneous condition characterized by multiple cystic and solid nodules appearing on the face.

Treatment for NPS varies depending on the symptoms observed.

- Perform screening for renal disease and glaucoma, surgery, intensive physiotherapy, or genetic counseling.

- ACE inhibitors are taken to treat proteinuria and hypertension in NPS patients.

- Dialysis and renal transplant.

- Physical therapy, bracing and analgesics for joint pain.

- Other surgery treatments such as patella realignment, joint replacement, and the cutting away of the head of radius.

When a patient has multiple abnormalities (multiple anomaly, multiple deformity), they have a congenital abnormality that can not be primarily identified with a single system of the body or single disease process. Most medical conditions can have systemic sequelae, but multiple abnormalities occur when the effects on multiple systems is immediately obvious.

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.

Subungual exostoses are bony projections which arise from the dorsal surface of the distal phalanx, most commonly of the hallux.