Eruptive collagenoma. Apropos of a case with ultrastructural study

A 29-year-old male patient was examined for numerous asymptomatic dermal nodules symmetrically distributed over the back and the shoulders. The nodules were firm, round to oval and varied in size from a few millimeters to 2 centimeters. They had appeared in normal skin without any known previous inflammation or injury, and they has been present without modification for nine years. At histological examination a dermal accumulation of abundant and large collagen bundles was observed. Elastic fibers seemed to be less numerous than normally. Alcian blue showed no increase in acid mucopolysaccharides. An ultrastructural study displayed normal, mature collagen fibers arranged in large bundles. Cutaneous collagenoma, initially described by Colomb as "eruptive collagenoma" is a rare disorder of unknown etiology occurring in young adults as symptomless dermal nodules without previous history of illness or injury and mostly localized to the back. No change is usually observed in these nodules for several years. Histologically, the nodules are characterized by a proliferation of collagen in the dermis; elastic fibers are generally reduced in number. Our ultrastructural study showed that proliferation of normal collagen fibers is the main morphological finding.