ASXL1 mutated chronic myelomonocytic leukemia in a patient with familial thrombocytopenia secondary to germline mutation in ANKRD26

Thrombocytopenia 2 (THC2), a non-syndromic, autosomal dominant thrombocytopenia, is caused by mutations in the ANKRD26 gene, located on chromosome 10p12.1 Thus far, 12 heterozygous single nucleotide substitutions in the 5′-untranslated region of the ANKRD26 gene have been described in 21 families.2, 3 Affected patients usually present with moderate thrombocytopenia with normal platelet size and normal mean platelet volumes. Many patients were reported to have an α-granule deficiency as detected by immunofluorescent labelling without consistent defects in platelet aggregation studies. Evidence for dysmegakaryopoiesis has been observed in a small number of patients who have undergone bone marrow biopsies. Surprisingly, a small subset of individuals can have elevated hemoglobin levels and leukocyte counts, without a clear explanation.3