Overview of Inherited Zinc Deficiency in Infants and Children.

Zinc nutrition is of special practical importance in infants and children. Poor zinc absorption causes zinc deficiency, which leads to a broad range of consequences such as alopecia, diarrhea, skin lesions, taste disorders, loss of appetite, impaired immune function and neuropsychiatric changes and growth retardation, thus potentially threatening life in infants and children. In addition to dietary zinc deficiency, inherited zinc deficiency, which rarely occurs, is found during the infant stage and early childhood. Recent molecular genetic studies have identified responsible genes for two inherited zinc deficiency disorders, acrodermatitis enteropathica (AE) and transient neonatal zinc deficiency (TNZD), clarifying the pathological mechanisms. Both of these zinc deficiencies are caused by mutations of zinc transporters, although the mechanisms are completely different. AE is an autosomal recessive disorder caused by mutations of the ZIP4 gene, consequently resulting in defective absorption of zinc in the small intestine. In contrast, TNZD is a disorder caused by mutations of the ZnT2 gene, which results in low zinc breast milk in the mother, consequently causing zinc deficiency in the breast-fed infant. In both cases, zinc deficiency symptoms are ameliorated by a daily oral zinc supplementation for the patients. Zinc is definitely one of the key factors for the healthy growth of infants and children, and thus zinc nutrition should receive much attention.