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Question . 1. A 10-day-old infant develops an annular, scaly, erythematous eruption

on the forehead. He was born at term after an uncomplicated delivery, with a past

medical history significant only for hyperbilirubinemia treated with phototherapy.

Results of a KOH examination are negative. His mother has intermittent episodes of

joint pain. The most appropriate next step in diagnosis is:

A. Liver function tests

B. Fungal culture

C. Skin biopsy

D. Autoimmune work-up

Explanation: This vasculitic-type rash is compatible with neonatal lupus.

Maternal antibodies cross the placenta (IgG) and produce autoimmune

phenomena in the baby. These include hemolytic anemia, thrombocytopenia,

neutropenia, cutaneous vasculitis, and congenital heart block. All

manifestations except heart block resolve with time. E would also be correct.

Neonatal lupus should be considered diagnostically based on the age at

presentation, morphology of rash, and history of UV light exposure. NLE

babies can have ECG abnormalities, but only 1 in 10 has both ECG changes

and a rash. Therefore, because a rash is present, the next best step

diagnostically would be serum assay for autoantibodies, which should be

diagnostic. (See Chapter 637 in Nelson Textbook of Pediatrics, 17th ed.)

E. Electrocardiogram