Aplasia cutis congenita in dizygotic twin infants

ABSTRACT

Aplasia cutis congenita (ACC) is often sporadic, but familial cases have been reported. We report a case of a dichorionic diamniotic twin pregnancy in which both the male and female twins had matching areas of aplasia cutis on their scalps. An Irish couple sought fertility treatment using a donor egg and paternal sperm. Successful in vitro fertilization (IVF) and the transfer of two embryos resulted in a diamniotic dichorionic twin pregnancy. Two fetal poles were noted at the 12-week ultrasound (US) scans. The mother suffered from a minor urinary tract infection during the first trimester but had no other history of infection, including herpes simplex virus or COVID- 19. She was known to be varicella immune prior to pregnancy. The twins were born by elective caesarean section owing to breech presentation. Twin one was female and twin two was male. Both infants were born with scarring on the crown of their head, which was consistent with ACC. Cranial US showed no underlying bony abnormality. The rest of the cutaneous examination was normal and there were no other congenital anomalies. ACC is a rare, heterogeneous group of disorders characterized by the congenital absence of skin, which can be focal or widespread. It is thought to affect 1-3 per 10 000 live births. The exact cause of ACC is unclear. Various hypotheses have been suggested, including defective closure of the neural tube or embryonic fusion lines, intrauterine trauma, placental insufficiency, fetus papyraceus, amniotic membrane adhesions, intrauterine infections, teratogens and genetic mutations. The classification of ACC is based on the area affected, type of skin irregularity, associated congenital defects and mode of inheritance. Scalp ACC without multiple anomalies (category 1) is generally associated with an autosomal dominant or sporadic pattern of inheritance. These twins may have an autosomal dominant mutation that led to this phenotype. ACC can also be associated with fetus papyraceus or placental infarct. This is less likely in this case as only two embryos were transferred, and the pregnancy was dichorionic. Most cases of ACC associated with fetus papyraceus occur in monozygotic pregnancies. ACC lesions often heal spontaneously by re-epithelialization resulting in a hairless superficial scar. Twin one had a slightly smaller area affected by ACC and overlying eschar resolved several weeks after birth. Twin two has had no hair growth in the area. This case highlights the difficulties in ascertaining the aetiology of this rare condition in twin pregnancies.