Subungual exostoses are a type of non-cancerous

bone tumor A bone tumor is an abnormal growth of tissue in bone, traditionally classified as noncancerous (benign) or cancerous (malignant). Cancerous bone tumors usually originate from a cancer in another part of the body such as from lung, breast, thyr ...

of the chondrogenic type, and consists of

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...

and cartilage. It usually projects from the upper surface of the

big toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''planti ...

underlying the nailbed, giving rise to a painful swelling that destroys the nail. Subsequent ulceration and infection may occur. There is an association with trauma and infection. Diagnosis involves medical imaging to exclude other similar conditions, particularly osteochondroma.

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

appearance may reveal a bony protuberance attached to the top or side surface of a toe bone. Treatment is by surgical excision and is effective. More than half are under the age of 18 years and males are affected equally to females. Combined with bizarre parosteal osteochondromatous proliferation, they comprise <5% of cartilage tumors.

Signs and symptoms

They tend to be painful due to the pressure applied to the nail bed and plate. They can involve destruction of the nail bed. These lesions are not true osteochondromas, rather it is a reactive cartilage metaplasia. The reason it occurs on the dorsal aspect is because the periosteum is loose dorsally but very tightly adherent volarly.Murphey MD, Choi JJ, Kransdorf MJ, et al: Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation. Radiographics 20:1407-1434, 2000

Diagnosis

Diagnosis involves medical imaging. Differential diagnosis includes mainly bizarre parosteal osteochondromatous proliferation (BPOP), which is more irregular and tends to involve the middle of the finger or toe rather than the end near the nail. They are distinct from subungual osteochondroma.

Treatment

Treatment is by surgical excision and is effective. File:Subungual_exostosis_02.JPG, Subungual exostosis (2/3) File:Subungual_exostosis_03.JPG, Subungual exostosis (3/3), after excision

Epidemiology

It tends to occur in children and adolescents. Combined with BPOP, they account for less than 5% of cartilage tumors.

References

External links