Introduction - Acrodermatitis enteropathica
Introduction
Demographics
Causes
Clinical features
Complications
Diagnosis
Differential diagnoses
Treatment
Outcome
Acrodermatitis enteropathica is a rare genetic disorder of zinc metabolism characterised by the triad of dermatitis, diarrhoea, and alopecia [1]. 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 dysmetabolica).
An acrodermatitis enteropathica-like condition can be categorised as secondary to acquired zinc deficiency or to a metabolic disorder unrelated to zinc deficiency [1].
Causes of acquired zinc deficiency include [1-4]:
Acrodermatitis dysmetabolica refers to acrodermatitis enteropathica-like eruptions associated with various metabolic disorders.
Acrodermatitis dysmetabolica is caused by deficiencies in essential amino acids (notably isoleucine), fatty acids, or cofactors such as biotin. These deficiencies can occur as a consequence of overly restrictive dietary treatments, or as a direct result of the underlying defect
Metabolic disorders responsible for acrodermatitis enteropathica-like conditions include [1–3]:
Necrolytic migratory erythema can present with a rash similar to acrodermatitis enteropathica in adults and is associated with glucagonoma [1].
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 [1].
In metabolic disorders, amino acid or fatty acid deficiency leads to reduced keratinocyte growth and differentiation [1].
Like its namesake, an acrodermatitis enteropathica-like condition typically presents with the triad of dermatitis, diarrhoea, and alopecia [2].
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]:
An acrodermatitis enteropathica-like condition can be complicated by secondary bacterial infection or candidiasis [1].
Decompensation of a congenital metabolic disorder during periods of illness or stress may result in acidosis, which is potentially fatal [5]. 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 [2]. Zinc levels and alkaline phosphatase tend to be normal in acrodermatitis enteropathica-like conditions related to metabolic disorders [1].
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 [5]:
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 [5].
A skin biopsy of an acrodermatitis enteropathica-like condition has non-specific histopathology; epidermal pallor and confluent parakeratosis may be observed [7].
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 [2]. 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 [5]. Expert assistance should be sought from a nutritionist.
The outcome for an acrodermatitis enteropathica-like condition depends on the underlying condition.
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 [9].
An acrodermatitis enteropathica-like condition secondary to a metabolic disorder can have a high mortality rate in the newborn period if undiagnosed. This is mitigated to some extent by detection in the newborn period with the help of screening programmes [5]. A significant number of children diagnosed early with congenital metabolic disorders will still have ongoing problems with metabolic crises and neurocognitive development [5,6].
