Thrombocytopenia-3 (THC3) is an autosomal recessive hematologic disorder characterized by onset of small-platelet thrombocytopenia in infancy. Patients may show variable bleeding tendency, manifest as petechiae, epistaxis, or heavy menstrual bleeding (summary by Levin et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of thrombocytopenia, see 313900.