[Lipoatrophia semi-circularis of the thigh].

Two typical cases of this apparently rare condition usually observed in women are reported. 22 cases have been published since the first observation in 1974. Lesions are made of semi circular band-like, isolated, atrophy of the subcutaneous fatty tissue, involving half the circumference of anterolateral part of the thigh. No other clinical or biological abnormalities are noticed. Four stages may be histological considered. Ultrastructural investigation performed in our cases confirms histological findings: in the first case adipocyte's abnormalities, fibrillogenesis, and sclerosis are noticed, in the second case (persistent lipoatrophia) rarefaction of collagen's fibers appears to be the most important feature. Etiology remains unclear, but repeated external traumas seem the most plausible explanation in several cases of the literature and in our cases: case no. 1, related to leaning on bath's border for washing, was regressive after trauma's suppression, while the second case was not regressive since the patient did not discontinue wearing the responsible girdle.