Immune Thrombocytopenia in Type I Gaucher Disease.

Backgound: Type I Gaucher disease (GD) the non-neuronopathic form is characterized by hepatosplenomegaly, pancytopenia and skeletal complications due to the accumulation of glucocerebroside in macrophages. Thrombocytopenia is usually related to hypersplenism and/or infiltration of bone marrow by the lipid-laden macrophages namely Gaucher cells. Enzyme replacement therapy (ERT) restores the hemoglobin and platelet count in treated GD patients within 12–24 months of treatment. In GD patients, including ERT treated, with persistent low platelet counts other ethiological factors should be considered.

Goals: To determine the etiology of persistent thrombocytopenia in Type I GD patients and to evaluate their clinical course and hematological parameters.

Methods: Flow cytometric technique was used to detect platelet-surface associated IgG/M (PSIgG/M) in a cohort of 24 Type I GD patients followed at the Gaucher clinic in Haifa, Israel. The evaluated hematological parameters of the thrombocytopenic GD patients include: bleeding phenomena, concurrence of autoimmune phenomena, hematological malignancies and bone marrow findings.

Results: Twenty four Type I GD patients, 15 females and 9 males with an age range of 35 to 80 years (median 53 years) were included in the study. Seventeen of the evaluated 24 patients were thrombocytopenic with platelet counts less than <100×10⁹/l and 7/24 were in the normal range. Bone marrow aspirate was performed in 16 of the 17 thrombocytopenic patients and showed normal or hyperplasic megakariopoiesis together with Gaucher cells infiltrates. Six of the 17 thrombocytopenic patients received ERT for at least 24 months with no effect on the low platelet counts. Elevated platelet surface IgG was detected in 16/17(94%) of GD patients with thrombocytopenia and in only 1/7 (14%) of non thrombocytopenic patients (p<0.0001). In 6/17 of the thrombocytopenic patients, surface IgM (PSIgM) was found, in addition to the PSIgG. Those six patients are known with monoclonal IgM (concomitant Waldenstrom macroglobulinemia), markedly elevated polyclonal IgM levels, or lupus like autoimmune disorder which may have been responsible for the positive PSIgM. Only three thrombocytopenic patients with platelet counts less than 40×10⁹/l had bleeding tendency (mainly purpura) with no response to steroid treatment (two of them were also resistant to ERT concerning their thrombocytopenia).

Conclusions: Thrombocytopenia in Type I GD is related to either infiltration of bone marrow compromising megakariopoiesis or hypersplenism, but immune factors should also be considered. Despite the lack of response to steroids, the observed megakaryocytic hyperplasia in Gaucher infiltrated marrows, the failure to respond to ERT, and the presence of platelet surface antibodies in the thrombocytopenic patients, strongly implicate autoimmune etiology. The present study demonstrates that surface platelet antibodies may play a role in refractory thrombocytopenic GD patients. Since the role of splenectomy is controversial in GD, immune modulation approach should be considered.