Non-caseating granulomata associated with hypocellular myelodysplastic syndrome

Non-caseating granuloma (NCG) remains a histopathological hallmark for sarcoidosis. Although the exact mechanism for NCG formation is unknown, the pathogenesis may involve a disordered antigen presentation in the monocyte/macrophage system, functional abnormalities in activated T-lymphocytes and uncontrolled cytokine production. Similar immunological dysfunction has been described in myelodysplastic syndrome (MDS). However, the association of NCG and MDS is rarely documented. We report a case of hypocellular MDS associated with generalized NCG. Despite treatment for both sarcoidosis and tuberculosis, the patient failed to respond. A clonal myeloid disorder which was initially suppressed by T-cell immunosurveillance evolved after treatment with anti-thymocyte globulin. Although the coexistence of sarcoidosis remains a possibility, the lack of supportive clinical evidence of sarcoidosis, the abnormal appearances of the bone marrow, together with the failure to improve on high-dose steroid favour the clonal myeloid disorder as the sole pathology.