My 10 month old baby has very thick toenails, like you'd see with arterial disease. he's had this since birth; what could cause this in an infant?

See Your Doctor: Your 10 mos old has "very thick toenails since birth". Congenital anomalies of the nails, hair, skin, teeth can be caused by a group of genetic defects called Ectodermal Dysplasias, of which there are numerous types. Involved body parts can be poorly developed or absent. Nails can be thick, misshapen or rough but usually cause no problems. See your doctor for diagnosis, genetic history, & therapy.