[Atypical eruptive collagenoma: two cases]. / Collagénomes éruptifs atypiques: deux cas.

BACKGROUND: Eruptive collagenoma is a rare cutaneous lesion seen in young adults. It consists of asymptomatic, flesh-coloured papules that are usually localised on the trunk and the root of the upper limbs. Herein we report two cases on account of the atypical topography of the lesions and the advanced age of the patients. CASE REPORTS: Case n 1: a 69-year-old man consulted for firm, whitish papules on the wrists, elbows, popliteal fossae and groin without associated signs, and which first appeared several years earlier. The standard laboratory assessment and ocular fundus test were normal. Case no 2: a 69-year-old woman had very firm, flesh-coloured papules on the trunk and the root of the limbs, which appeared after the age of 40. The results of ocular fundus, cardiovascular investigation and laboratory examinations were normal. The histology of papules was similar in both cases and revealed a nodular zone in the reticular dermis, comprising disorganized collagen bundles and excessive quantities of elastic fibres, without elastorrhexis. This histology was consistent with collagenoma. DISCUSSION: We report two singular cases that were atypical in terms of patient age and localisation in the flexion folds. Histological analysis of a papule enables a diagnosis of collagenoma to be made. Such analysis usually reveals a hamartoma in which the amount of collagen is increased, with variable quantities of elastic tissue, though often decreased. The principal differential diagnoses are elastoma and pseudoxanthoma elasticum.