Hardened plaque on a neonate's back

A full-term, healthy female infant was born to a woman aged 24 years. It was the mother's first pregnancy and was complicated by gestational diabetes and borderline hypertension. APGAR scores were 8 and 9, despite the presence of meconium staining at birth.

Two weeks after discharge, the infant was brought to the pediatrician because the mother was worried about a rash ...