A newborn develops flaccid blisters and superficial erosions on day 3 of life. The mother has active pemphigus vulgaris. The neonatal eruption is best explained by:

• A Transplacental transfer of maternal IgG against desmoglein-3, resolving spontaneously within weeks ✓
• B Autosomal dominant inheritance of a desmoplakin mutation
• C Maternal IgM crossing the placenta during labour
• D De novo development of autoantibodies against collagen VII in the infant

Explanation

Neonatal pemphigus results from passive transfer of maternal pathogenic IgG across the placenta. Only IgG crosses the placenta, which is why maternal IgM cannot cause disease. The blisters resolve within days to weeks as maternal antibody is cleared, and the infant does not develop persistent autoimmune disease. Collagen VII antibodies define epidermolysis bullosa acquisita, an acquired adult disorder.

Reference: Fitzpatrick's Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.