Two Cases of Aplasia Cutis Congenita With Hair Collar Signs and Macrophage Hyperplasia

The document reported two cases of aplasia cutis congenita with hair collar signs and hemangioma simplex in the parietal regions. These signs typically suggest potential underlying neural tube defects, but no bone defects or heterotopic neural tissue were found in imaging and histopathological examinations. Both cases showed abnormalities in ectodermal fusion, with a flat epidermis and absence of appendages. Melanocytes were present in the superficial dermal layer, and there was an increase in macrophages in the dermal area, which lacked elastic and normal collagen fibers. Peripheral hair follicles were observed to grow horizontally.