A gain-of-function variant in the Wiskott-Aldrich syndrome gene is associated with a MYH9-related disease-like syndrome

While loss-of-function variants in the WAS gene are associated with Wiskott-Aldrich syndrome and lead to microthrombocytopenia, gain-of-function variants of WAS are associated with X-linked neutropenia (XLN) and absence of microthrombocytopenia. Only few XLN families have been reported so far and their platelet phenotype was not described in detail. To date, no renal involvement was described in XLN. In the present study we report exome sequencing of individuals from three generations of a family with a dominant disease combining neutropenia, macrothrombocytopenia and renal failure. We identified a heterozygous missense gain-of-function variant in the WAS gene (c.881T>C, p.I294T) that segregates with the disease and is already known to cause XLN. There was no pathogenic variant in MYH9, TUBB1 or ACTN1. This is the first report of a WAS gain-of-function variant associated with both the hematological phenotype of XLN (neutropenia, macrothrombocytopenia) and renal disease (proteinuria, renal failure) with glomerular tip lesion hyalinosis and actin condensations in effaced podocytes foot processes.