Letters to the Editor
To the Editor: Acrodermatitis enteropathica (AE) is an autosomal-recessive disorder of gastrointestinal zinc absorption (1,2). We describe 2 siblings who presented with signs and symptoms of zinc deficiency, plasma zinc concentrations just below the normal range, and who are now dependent on zinc supplementation to avoid recurrence.
A 3-year-old girl presented with a 5-month history of a worsening eczematous rash. She had been treated for impetigo, atopic eczema, fungal and viral infections, candidiasis, and cystitis. She had behavioural changes, withdrawal, tiredness, lethargy, poor appetite, and slow weight gain for 1 year before presentation. The topical application of zinc sulphate ointment resulted in slight improvement of the rash.
She had a symmetrical eczematous eruption in the anogenital and orofacial areas (Figs 1 and 2), with thin and lustreless hair. The plasma zinc concentration was 9.2 μmol/L (normal range 9.8–17 μmol/L) and alkaline phosphatase 104 IU/L (normal range 108–317 IU/L). She was started on oral zinc sulphate, 30 mg/day, with rapid resolution in all of her symptoms and acceleration of growth.
Her younger sibling presented at 10 months with lethargy and a rash in the anogenital area and around her ears and axillae, but less severe than in her sister's case. The plasma zinc concentration was 9.1 μmol/L.
Both siblings are currently taking zinc 112.5 mg/day and maintain plasma zinc concentrations of 15 to 21 μmol/L. Plasma copper and selenium were normal. Any attempt to reduce the dosage has resulted in relapse, with deterioration in skin, mood, activity, behaviour, and appetite.
The girls' maternal grandfather had problems with fertility, long-standing depression, anorexia, thin hair, and extreme tiredness. His plasma zinc was found to be 8.1 μmol/L, rising to 11.3 μmol/L on a 45-mg zinc supplement, and he is well. Screening for mutations in the SLC394A gene (AE gene) was negative in both sisters. This suggests that these siblings have a distinct zinc metabolic defect with possible dominant inheritance and variable penetrance, resulting in functional zinc deficiency.
AE is the only well-established form of inherited zinc-deficiency disorder (3). The differential diagnosis of AE includes nutritional deficiencies such as biotin deficiency, kwashiorkor, and essential fatty acid deficiency (3). Acquired zinc deficiency in childhood is seen mostly in prematurity, parenteral nutrition, Crohn disease, cystic fibrosis, HIV, malabsorption syndromes, and malignancy (3). A mutation in SLC30A2 in breast-feeding mothers has been noted, preventing zinc secretion in breast milk, resulting in zinc deficiency in their infants (4). There was no suggestion that clinical zinc deficiency reported in the 2 siblings was caused by any of these disorders. The mechanism of the genetically determined late-onset zinc deficiency in this family remains to be elucidated.
1. Ackland ML, Michalczyk A. Zinc deficiency and its inherited disorders—a review. Genes Nutr
2. Kaur S, Thami GP, Kanwar AJ. Acrodermatitis enteropathica in a full-term breast-fed infant. Indian J Paediatr 2002; 69:631–633.
3. Gehrig KA, Dinulos JGH. Acrodermatitis due to nutritional deficiency. Curr Opin Pediatr 2010; 22:107–112.
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4. Chowanadisai W, Lonnerdal B, Kelleher SL. Identification of a mutation in SLC30A2 (ZnT-2) in women with low milk zinc concentration that results in transient neonatal zinc deficiency. J Biol Chem 2006; 281:39699–39707.