Light and electron microscopy of eruptive collagenoma

Connective tissue nevi may be multiple or solitary, sporadic or familial. Eruptive collagenoma is a variant of the acquired collagenomas characterized by multiple sclerotic papules with an acute onset. A 13-year-old girl reported that in the past year, small asymptomatic lesions began to appear in her skin, 30 lesions were seen in the trunk, 5 in the cervical region and 1 in the face. Light microscopy with hematoxylin and eosin staining showed sparse collagen fibers, with Weigert staining diminished elastic tissue was observed. Scanning electron microscopy of the dermis showed individualized collagen fibers forming waved compact masses and not bundles. Transmission electron microscopy also showed sparse and loose collagen fibers with different diameters in cross sections.