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Author: Leah Jones, Medical Registrar, Christchurch, New Zealand. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. May 2020.
Acrodermatitis enteropathica is a rare genetic disorder of zinc metabolism characterised by the triad of dermatitis, diarrhoea, and alopecia . It is an autosomal recessive condition caused by a mutation in the SLC39A4 gene, which codes for a zinc transporter protein [1,2].
An acrodermatitis enteropathica-like condition presents with similar features to acrodermatitis enteropathica, but is caused by acquired zinc deficiency or a disorder of amino acid or fatty acid metabolism .
Acrodermatitis enteropathica-like conditions include:
An acrodermatitis enteropathica-like condition can be categorised as secondary to acquired zinc deficiency or to a metabolic disorder unrelated to zinc deficiency .
Causes of acquired zinc deficiency include [1,2,4]:
An acrodermatitis enteropathica-like condition related to a metabolic disorder can be secondary to:
Acrodermatitis enteropathica-like conditions secondary to metabolic disorders are caused by abnormalities disrupting the metabolism of amino acids or fatty acids . This can be direct, through disruption of the urea cycle, or by affecting co-factors, notably biotin [1–3].
Metabolic disorders responsible for acrodermatitis enteropathica-like conditions include [1–3]:
Necrolytic migratory erythema can also present with a rash similar to acrodermatitis enteropathica in adults and is associated with glucagonoma .
When an acrodermatitis enteropathica-like condition is related to acquired zinc deficiency, the lack of zinc leads to abnormal keratinisation, cell proliferation, and defective immune response .
In metabolic disorders, amino acid or fatty acid deficiency leads to reduced keratinocyte growth and differentiation .
The cutaneous features of an acrodermatitis enteropathica-like condition include [1–3]:
Other features of an acrodermatitis enteropathica-like condition depend on the underlying cause, but often include [1,3,5]:
Decompensation of a congenital metabolic disorder during periods of illness or stress may result in acidosis, which is potentially fatal . Long-term neurodevelopmental problems are not uncommon in congenital metabolic disorders [1,5,6].
Acquired zinc deficiency is associated with low serum zinc levels and alkaline phosphatase . Zinc levels and alkaline phosphatase tend to be normal in acrodermatitis enteropathica-like conditions related to metabolic disorders .
A full blood count may reveal cytopenias in both acquired zinc deficiency and metabolic disorders [2,5].
The initial blood tests for an organic acidaemia may include :
Levels of specific amino acids or enzyme activity and the presence of organic acids in the urine may support a specific diagnosis [1,5].
Newborn screening detects many of the congenital metabolic causes of acrodermatitis enteropathica-like conditions and is available in many parts of the world including New Zealand, Australia, the United Kingdom, the United States, and Canada .
A skin biopsy of an acrodermatitis enteropathica-like condition has non-specific histopathology; epidermal pallor and confluent parakeratosis may be observed .
The differential diagnosis of an acrodermatitis enteropathica-like condition includes:
An acrodermatitis enteropathica-like condition secondary to acquired zinc deficiency will resolve after oral zinc supplementation, usually at an initial dose of 0.5–1 mg/kg/day of elemental zinc . Whether there is an ongoing need for zinc replacement will depend on the cause [2,8].
An acrodermatitis enteropathica-like condition secondary to a metabolic disorder generally responds to dietary manipulation and medication in the form of specific organic supplements to correct metabolic deficiencies . Expert assistance should be sought from a nutritionist.
The outcome for an acrodermatitis enteropathica-like condition differs depending on whether the condition is secondary to an acquired zinc deficiency or a metabolic disorder.
An acrodermatitis enteropathica-like condition secondary to acquired zinc deficiency has a favourable prognosis if identified early [8–9]. The dermatological, gastrointestinal, and psychological manifestations tend to resolve within days to weeks following zinc replacement .
The prognosis of an acrodermatitis enteropathica-like condition secondary to a metabolic disorder depends on the underlying condition. There is a high mortality rate in the newborn period that is mitigated to some extent by diagnosis in the newborn period with the help of screening programmes . A significant portion of children with congenital metabolic disorders will have ongoing problems with metabolic crises and neurocognitive development [5–6].
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