Clinical heterogeneity can hamper the diagnosis of patients with ZAP70 deficiency.

[omenn syndrome]

One of the severe combined immunodeficiencies (SCIDs ), which is caused by a genetic defect in the signal transduction pathways involved in T -cell activation , is the ZAP 70 deficiency . Mutations in ZAP 70 lead to both abnormal thymic development and defective T -cell receptor (TCR ) signaling of peripheral T -cells . In contrast to the lymphopenia in most SCID patients , ZAP 70 -deficient patients have lymphocytosis , despite the selective absence of CD 8 + T -cells . The clinical presentation is usually before 2 years of age with typical findings of SCID . Here , we present three new ZAP 70 -deficient patients who vary in their clinical presentation . One of the ZAP 70 -deficient patients presented as a classical SCID , the second patient presented as a healthy looking wheezy infant , whereas the third patient came to clinical attention for the eczematous skin lesions simulating atopic dermatitis with eosinophilia and elevated immunoglobulin E (IgE ), similar to the Omenn syndrome . This study illustrates that awareness of the clinical heterogeneity of ZAP 70 deficiency is of utmost importance for making a fast and accurate diagnosis , which will contribute to the improvement of the adequate treatment of this severe immunodeficiency .