STK4 (MST1) deficiency in two siblings with autoimmune cytopenias: A novel mutation

•A novel STK4 gene defect was identified in two siblings with overlapping features of DOCK8 defect.•Patients had bacterial and cutaneous viral infections and mild atopic/seborrheic dermatitis.•Tazammune cytopenia, lymphopenia (particularly CD4), and intermittant neutropenia were additional features.•Clinical/immunological features of the patients were compared.with those of DOCK8 deficiency.•Patients with overlapping features of AR-HIES should also be searched for STK-4 deficiency.

Combined immunodeficiencies (CIDs) are heterogeneous group of disorders characterized by abrogated/impaired T cell development and/or functions that resulted from diverse genetic defects. In addition to the susceptibility to infections with various microorganisms, the patients may have lymphoproliferation, autoimmunity, inflammation, allergy and malignancy. Recently, three groups have independently reported patients having mutations in STK4 gene that cause a novel autosomal recessive (AR) CID. We describe here two siblings with a novel STK4 mutation identified during the evaluation of a group of patients with features highly overlapping with those of DOCK-8 deficiency, a form of AR hyperimmunoglobulin E syndrome. The patients' clinical features include autoimmune cytopenias, viral skin (molluscum contagiosum and perioral herpetic infection) and bacterial infections, mild onychomycosis, mild atopic and seborrheic dermatitis, lymphopenia (particularly CD4 lymphopenia), and intermittent mild neutropenia. Determination of the underlying defect and reporting the patients are required for the description of the phenotypic spectrum of each immunodeficiency.