A 18 year-old-man with nail problem since birth… . 

The diagnosis is ?

Diagnosis: Congenital Anonychia

Absence of the nails from birth is a rare congenital anomaly with uncertain mode of inheritance. Anonychia may be isolated or be accompanied by other defects and Nail-Patella syndrome should be kept in mind in differential diagnosis.

Comment by Dr.M. Mehravaran, Szeged/Hungary:

In general partial or complete loss of the nail plate, may be congenital or may result from permanent damage to the nail matrix from trauma, and from destructive disorders such as lichen planus. Other conditions that lead to matrix destruction including peripheral vascular insufficiency, Raynaud's disease, inflammatory dermatoses and burns.Epidermolysis bullosa, lichen planus, Darier's disease, and leprosy may cause onychoatrophy....

Congenital onychodysplasia of index fingers. This syndrome (named COIF by Barn in 1980) was first observed by Iso, and categorized and named by Kikuchi in 1974. Criteria for diagnosis: presence at birth, index finger involvement (unilateral or bilateral), variable distortion of nail or lanula, polyonychia, micronychia, anonychia, hemionychogryphosis or malmaligment.