What was causing a scaly rash on this infant’s face? | Medical Mystery

“His ringworm is spreading” an exasperated first-time mother told me as she cradled her 6-week-old son.

Ringworm is caused by several superficial fungal infections. It’s benign and easily treatable with anti-fungal creams. But this mother was frightened by the circular lesions on her baby’s face that had gotten worse since he was diagnosed at 3 weeks old.

He’d developed a rash on his chin that was being treated with Lotrimin, an antifungal cream, but it had spread and become scaly. His mother worried that he might be allergic to the medication.

His mother had a routine pregnancy and birth, and aside from anxiety worsened by her son’s condition, she was also in good health.

Benign rashes are common among newborns and infants because their skin is much thinner than that of older children and adults. This type of rash goes away as an infant’s skin develops and maternal hormones dissipate in the six months after birth.

Looking at the pattern and appearance of this spreading rash, I knew that, unfortunately, this was not one of the benign rashes, and I immediately ordered some lab tests and an EKG.

The circular rashes also had a darker hue and were deeper in the skin than typical ringworm. They had a distinct disc shape to them and were concentrated on the only area of the body that was exposed to the sun.

The diagnosis? Neonatal lupus erythematosus (NLE), an uncommon condition that occurs in about one of every 20,000 infants. The infant doesn’t have lupus and, typically, neither does the mother.

But mothers of infants who develop NLE have circulating antibodies that cross the placenta, and they can affect not just the skin, but also the blood cells, liver, brain, and the most serious complication, the electrical system of the heart.

Thankfully, my patient’s EKG and blood tests for anemia and low red blood cells as platelets, as well as liver tests, were all normal. Even more important, his EKG was normal — essentially ruling out the most serious complication of the heart, where the signal for the heart to beat is disrupted.

The tests for antibodies in both the mother and infant came back positive, confirming the diagnosis of NLE. The condition does not require treatment, and the lesions typically resolve without scarring by the time the baby is 6 months old.

At a follow-up last week, at 4 months old, the skin lesions were thinning out and slowly fading.

Daniel R. Taylor is advocacy director at St. Christopher’s Hospital for Children.