The many faces of stk4 deficiency

INTRODUCTION Serine-threonine kinase 4 (STK4) or mammalian sterile 20 -like protein kinase 1 (MST1) is the mammalian homolog of the Drosophila Hippo protein, which controls cell growth, apoptosis and tumorigenesis. STK4 deficiency is a rare autosomal recessive disease which leads to a combined immunodeficiency with severe T-cell neutropenia. In addition to susceptibility to various infections, patients are also at risk of haematological abnormalities, autoimmunity, allergies and malignancies.(1,2)