Two cases of aplasia cutis congenita with hair collar signs and macrophage hyperplasia

: We report two cases of aplasia cutis congenita associated with hair collar signs and hemangioma simplex in their parietal regions. A hair collar sign and a hemangioma are known to suggest the possibility of underlying neural tube defects. However, no obvious bone defects or heterotopic neural tissue were observed in the imaging and histopathological examinations. Nevertheless, some pathological observations similar in both cases suggested abnormalities in the process of ectodermal fusion. A flat epidermis and a lack of appendages were recognized. Both cases also exhibited the presence of melanocytes in a portion of the superficial dermal layer. An increase in the number of macrophages was observed in the dermal area with neither elastic fibers nor normal collagen fibers. The peripheral hair follicles grew horizontally.