ARPC1B and Wiskott-Aldrich syndrome: ARPC1B-deficient patients present with clinical and laboratory features suggestive of WAS, including dermatitis, thrombocytopenia with bloody diarrhea, vasculitis, recurrent infections, autoimmune and atopic diathesis95,96; in addition, episodes of macrophage activation syndrome have been reported in these patients [Fig. 5].94