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Babies who have genetic problems with absorbing zinc suffer from a condition called acrodermatitis enteropathica. Symptoms include severe rashes, primarily around the mouth and anus, and diarrhea. Supplementing the baby's diet with zinc resolves the symptoms, although the condition is lifelong.
Although the precise genes involved in the inherited zinc deficiency are not known, scientists suspect that a gene called SLC39A4 may be involved. This gene codes for a transporter protein, known as ZIP4, which moves zinc through membranes. Babies with the genetic condition cannot move zinc from milk through the intestinal membrane efficiently. The disorder is recessive, which means that the baby must inherit one copy of the mutated gene from each parent to have the disease. If he or she only inherits one bad copy, zinc metabolism is not affected.
Acrodermatitis enteropathica symptoms usually arise in the first days or weeks of a baby's life if he or she is fed artificial milk. Babies who are breastfed do not show symptoms until they are weaned onto solid foods. This difference is due to the fact that zinc from human milk is much more easily absorbed by the baby than zinc from cow's milk.
An affected baby usually has inflamed skin with pimples around the anus and mouth, although this rash can also be present on elbows, feet, knees, and around the eyes. The rash starts off as scaly, dry skin and turns into lesions. Diarrhea is another common symptom.
Hair loss is another symptom of acrodermatitis enteropathica, with eyelashes and eyebrows also affected. The baby's nail region can be inflamed, and the nails can develop ridges. The tongue can be red and shiny, and ulcers can develop in the mouth. The effect the disease has on the baby's skin can also lead to secondary infection by yeast or bacteria, and wounds do not heal as quickly as normal.
Zinc is essential to normal functions of the body, so babies afflicted with acrodermatitis enteropathica can also suffer long-term damage if they do not receive zinc supplementation. Stunted growth, neurological symptoms, and infection are all complications of lack of zinc. Affected babies usually are irritable and emotionally depressed as a result.
The symptoms of the disease begin to clear up as soon as zinc is administered. Prior to the discovery of zinc deficiency as the cause of the condition, the babies died within a few years of birth. Now, however, supplementation with zinc throughout life can prevent acrodermatitis enteropathica from causing any damage. Babies without inherited zinc deficiency but who do not obtain enough zinc in their diets can also suffer from similar conditions.