Definition:

Transient neonatal zinc deficiency (TNZD) is a disorder caused by loss-of-function mutations of the zinc transporter SLC30A2/ZnT2 gene, which results in low zinc breast milk in the mother, consequently causing zinc deficiency in the breast-fed infant. The main initial symptoms of zinc deficiency are dermatitis, diarrhea, alopecia, and loss of appetite. Currently, at least two zinc transporters from separate protein families are now known to be involved in the genetics of zinc deficiency. One is SLC39A4/ZIP4, which mutations can cause acrodermatitis enteropathica, zinc deficiency type (AEZ) [DS:H00212] with autosomal recessive inheritance. The other one is SLC30A2/ZnT2, the transporter responsible for supplying human milk with zinc. Mutations in this transporter cause TNZD with symptoms similar to AEZ but with autosomal dominant inheritance. The two diseases can be distinguished in affected infants. AEZ is fatal if zinc is not supplied to the infant after weaning, whereas TNZD is a genetic defect of the mother limiting the supply of zinc in the milk, and therefore the infant usually will obtain enough zinc once weaned. Furthermore, the mothers' blood zinc levels are normal, and zinc supplementation to the mother's diet fails to improve the zinc levels in the breast milk.