[Keratosis follicularis decalvans: nosological discussion of Siemens' disease. Apropos of 3 cases].

We describe 3 cases of keratosis follicularis decalvans (Siemens' disease): a 15 year old boy and a 7 year old boy and his father. They represent 2 different patterns of the disease with different clinical courses and genetic background: an autosomal dominant type of good prognosis with elevated argininemia and absence of follicular atrophy in both father and son, a sporadic type, clinically severe, with follicular atrophy. This raises the question of the nosology of the so-called Siemens' disease, since it includes actually different diseases of variable prognosis.