ABSTRACT
Eruptive collagenoma is a rare acquired type of connective tissue nevus that predominantly consists of collagen. It usually presents as multiple, asymptomatic, firm, flesh-colored or pink nodules or plaques that are symmetrically distributed over the trunk and upper extremities. Four cases of eruptive collagenoma in linear or zosteriform arrangements have been reported in the English literature. A 16-year-old boy presented with multiple asymptomatic erythematous papules and nodules on the left side of his sternal margin and the posterior side of his left neck. A punch biopsy taken from one of the nodules on the chest showed thickened collagen fibers in the dermis. Masson-Trichrome staining revealed an increase in the collagen fibers, which were broad and arranged haphazardly, and the elastic staining indicated a reduction in the elastic fibers in the dermis, which are findings that are consistent with collagenoma. We report a case of eruptive collagenoma that presented in a linear arrangement, which is a rare distribution pattern for connective tissue nevi.