Why the rash, hair loss, irritability in a 4-month-old?

As she rocked her 4-month-old infant in her arms, a visually upset young mother said, "I think my baby is falling apart and so am I." A quick glance at this previously healthy child confirmed her fears.

"He was doing great for the first few months and was so happy, but ever since I weaned him from breast feeding to formula to go back to work, he has almost become unrecognizable," she said. "He is constantly crying, is having diarrhea, and has this horrible rash on his face. I think his hair is coming out as well."

Our team listened closely to her saga of formula changes and various creams for his rashes. The scales indicated how serious the situation had become: The child hadn't gained any weight in the three weeks since his last appointment.

The physical exam was consistent with the mother's descriptions. The infant was very irritable and stared at us, seeming to plead for help. His once-thick hair was thinning, and he had a crusting rash around his mouth. The rash was also on his arms and legs as well as his buttocks. He appeared to be wasting away, with the skinny legs and arms typical of a child who was not gaining weight.

The symptoms pointed to some sort of malabsorption, where the body wasn't absorbing calories as it should. But why the rash and hair loss? Why the irritability?

Occam's razor is a logical principle attributed to medieval philosopher William of Ockham. In medicine, it comes down to this: When a patient has numerous symptoms, there usually is one unifying cause.

For our patient, the problem was to be found on the periodic table: zinc.

Worldwide, an estimated two billion people lack enough of this essential element for growth and health. Zinc deficiency is a major contributor to death in children in countries where malnutrition is endemic.

Our patient lived in Philadelphia, not a developing nation. Still, lab tests showed a zinc deficiency, confirming our suspicions that he has an uncommon condition called acrodermatitis enteropathica. Children with this disease do not absorb zinc well in the small intestine, causing the classic symptoms of failure to thrive, diarrhea, irritability, and rash. Untreated, it is usually fatal, but treatment is simple: zinc supplements.

Unlike formula, breast milk has components that enhance absorption of nutrients including zinc. That's why weaning was the turning point for our patient.

Within days of starting daily zinc supplementation, he started improving, and soon the mother had her healthy baby boy back again.