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Autosomal recessive hyper IgE syndrome (AR-HIES) is a very rare primary immunodeficiency characterized by highly elevated serum IgE levels, recurring staphylococcal skin abscesses and recurrent pneumonia. The same clinical triad is also present in the more frequent autosomal dominant HIES syndrome (AD-HIES; see this term). AR-HIES accounts for only a small minority of HIES cases, with less than 10 affected families reported so far. In contrast to AD-HIES, the AR variant is further characterized by extreme hypereosinophilia, susceptibility to viral infections such as Herpes simplex and Molluscum contagiosum, involvement of the CNS, a poorly defined T-cell defect and a high lethality. Although the eosinophilia is a common finding in both AD and AR-HIES it tends to be more severe in the AR variant. The dental, skeletal and connective tissue anomalies, as well as the characteristic facies and pneumatoceles present in AD-HIES are absent in AR-HIES. The etiology of AR-HIES remains largely unknown. One patient with an autosomal recessive phenotype was found to carry a homozygous mutation in the receptor associated tyrosine kinase TYK2 gene (19p13.2), but it has subsequently been shown that TYK2 deficiency is not a common cause of AR-HIES. |