Effective splenectomy in familial isolated thrombocytopenia

Familial dominant thrombocytopenia: clinical, biologic, and molecular studies

Inherited thrombocytopenias are a heterogenous group of disorders. Different criteria have been suggested to classify the forms, such as the inheritance mechanism and the platelet volume as well as the number and morphology of megakaryocytes. However, the classification is often descriptive, and the precise mechanism of thrombocytopenia still remains unknown. We describe the clinical, biologic, and molecular findings of an autosomal dominant thrombocytopenia in a large family. The 17 patients had normocellular bone marrow and normal platelet volume. Platelets also showed a normal aggregation test and normal response to ADP and thrombopoietin (TPO). In the affected subjects, the mean +/- SD levels of platelet count and plasma TPO were 62+/-25 and 258+/-151, respectively. Comparative analysis showed that the patients with platelet count <70000 had higher plasma TPO concentration. The data are consistent with a mild clinical form of the disease associated with only a few episodes of bleeding. To exclude the possible role of TPO and its receptor c-mpl in the etiology of this condition, linkage analysis was performed using microsatellite markers close to the TPO and c-mpl genes on chromosomes 3q26.3-q27 and 1p34, respectively. The absence of cosegregation within the affected family indicated that these genes, as well as two other candidate loci on chromosomes 11 and 21, are not responsible for this hereditary dominant form of thrombocytopenia. A genome-wide search and subsequent identification of the gene will provide new insight into the pathogenesis of this disorder.

An autosomal dominant thrombocytopenia gene maps to chromosomal region 10p

The increasing number of diagnosed cases of inherited thrombocytopenias, owing to the routine practice of including platelet counts in blood tests, suggests that this condition is not so rare as expected. In the majority of cases, the molecular basis of the disease is unknown, although the defect is likely to affect thrombocytopoiesis and regulation of the normal platelet count. Here we report a genomewide search in a large Italian family affected by autosomal dominant thrombocytopenia. Patients showed a moderate thrombocytopenia with minimal symptoms characterized by normocellular bone marrow, normal medium platelet volume, and positive aggregation tests. Microsatellite analysis demonstrated that the disease locus (THC2) is linked to chromosome 10p11.1-12, within a candidate region of 6 cM between markers D10S586 and D19S1639. A maximum LOD score of 8.12 at recombination fraction.00 was obtained with the microsatellite D10S588. These data localized the first locus of an autosomal dominant thrombocytopenia, and the subsequent identification of the gene will provide new insight into the basic mechanism of megakaryocytopoiesis disorders.