Supplementary Material for: Frieden’s Group-V Aplasia Cutis Congenita with In-Utero Scarring in a Dichorionic Twin: A Case Report and Comprehensive Literature Review

Aplasia Cutis Congenita (ACC) is a rare congenital disorder characterized by the localized absence of skin at birth, primarily affecting the scalp, but also affecting the trunk and limbs. This case report details a neonate diagnosed with Group V- ACC (G-V ACC) associated with fetus papyraceus from a dichorionic diamniotic twin pregnancy. Born to a 28-year-old Asian mother, the female infant presented with extensive, healed, scar-like lesions on her flanks and upper thighs. These lesions were consistent with the 'H'-shaped distribution commonly described in ACC linked to fetus papyraceus. Despite significant dermatological manifestations, the infant showed no other external abnormalities or systemic involvement, and comprehensive screenings, including ultrasounds and chromosomal microarray, were normal. This discussion highlights the rarity of ACC in such clinical contexts, with only a few over 100 cases reported globally. The pathogenesis is speculated to involve ischemia from acute hypovolemia or disseminated intravascular coagulation due to thrombotic tissue affecting the surviving twin. Management of ACC depends on lesion severity, focusing on preventing infection and promoting healing, with conservative measures in most cases and surgical intervention in some cases. The long-term prognosis for isolated G-V ACC is generally favorable unless associated with systemic complications. This case underscores the importance of recognizing the patterns and potential complications of ACC in twins, contributing to better diagnostic acumen and management strategies for neonatal care.