AK2 and lymphopenia: The disease is clinically characterized by congenital lymphopenia, lymphoid and thymic hypoplasia with agranulocytosis and sensorineural deafness (Hoenig et al., 2018) and is caused by mutations in adenylate kinase 2 (ak2) gene (Lagresle-Peyrou et al., 2009; Pannicke et al., 2009; Six et al., 2015).