Background: Harlequin Ichthyosis (HI) is an extremely rare and severe form of autosomal recessive congenital ichthyosis, most commonly associated with mutations in the ABCA12 gene. Prenatal diagnosis is challenging because characteristic phenotypic features may appear late in pregnancy.

Case Presentation: A 20-year-old primigravid woman presented at 32 weeks of gestation with undue abdominal enlargement and respiratory distress. Ultrasonography revealed polyhydramnios with no obvious structural abnormality on routine 2D examination. A subsequent 3D ultrasonographic assessment demonstrated characteristic abnormal facial features, including ectropion, eclabium, flattened nose, clenched hands and deformed feet. Based on these findings, a provisional diagnosis of fetal harlequin ichthyosis was made. The parents were counselled regarding the poor neonatal prognosis and opted for termination of pregnancy. Labour was induced with prostaglandin, resulting in the delivery of a male fetus with typical features of HI. The neonate had extensive thick, rigid, hyperkeratotic skin plaques separated by deep fissures, ectropion, eclabium, rudimentary ears, restricted limb movements and hypoplastic digits. Despite neonatal resuscitation and supportive care, the baby died shortly after birth due to severe respiratory distress.

Discussion: HI is caused predominantly by pathogenic variants in the ABCA12 gene, resulting in defective epidermal lipid transport and severe skin barrier dysfunction. Prenatal diagnosis may be achieved through molecular genetic testing, particularly in pregnancies at increased risk. Ultrasonography, especially 3D ultrasound, can identify characteristic facial abnormalities, limb deformities and other features, although phenotypic expression may be delayed. Early recognition allows appropriate counselling and perinatal planning.

Conclusion: Harlequin ichthyosis is a rare but potentially lethal congenital disorder that can be suspected antenatally by careful ultrasonographic assessment. In pregnancies at risk, molecular testing for ABCA12 mutations provides definitive prenatal diagnosis. Repeated detailed ultrasound examination, including 3D imaging when available, may facilitate diagnosis when molecular testing is not accessible. Genetic counselling should be offered to affected families for future pregnancies.

Jesika Rizvi Tamanna has completed her fellowship in Maternal and Fetal Medicine at her 40 years of age from Bangladesh Medical University under BCPS. She is working as a Feto-maternal Medicine specialist at Mugda Medical College and Hospital, Dhaka, with expertise in high-risk pregnancy, prenatal diagnosis, advanced obstetric ultrasound, invasive prenatal procedures, and minimally invasive gynecologic surgery.