Onychogryphosis is a hypertrophy that may produce nails resembling claws or a ram's horn, possibly caused by trauma or peripheral vascular disorders, but most often secondary to neglect and failure to cut the nails for extended periods of time. Onychogryphosis is most commonly seen in the elderly, and some recommend avulsion of the nail plate with surgical destruction of the matrix with phenol or the laser, if the blood supply is good.

Severe congenital Onychogryphosis affecting all twenty nailbeds has been recorded in two families, who exhibit dominant ineritance of the allele. Congenital Onychogryphosis of the distal toe (the little toe) is fairly common, but asymptomatic and seldom brought to the attention of medical professionals. Rather, it is brought to the attention of manicurists who routinely file the clawed toenail flat.