HIV-associated bone marrow changes

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Following the recognition of AIDS and the identification of HIV — the retrovirus responsible for its causation, it became apparent that abnormalities of bone marrow (BM) are commonly associated with abnormal peripheral blood findings in HIV infected patients. Anaemia, granulocytopaenia and thrombocytopaenia are frequently present and are reflected by the dyshaematopoiesis found in BM. Both bone marrow aspiration (BMA) and bone marrow trephine biopsies (BMTB) reveal alterations in cellularity (most often hypercellularity), dysplasia of 1, 2 or 3 cell lines; inflammatory and stromal reactions, opportunistic infections (OI) and involvement by high grade lymphomas. The mechanisms responsible for the haematological abnormalities in HIV positive individuals are numerous and are not mutually exclusive; they include the CDC class of the disease, the effects of treatment, the presence of infection and lymphoma (and other malignant diseases), immunological mechanisms and damage to BM cells (stromal cells, stem cells, differentiated macrophages and megakaryocytes) as a result of their direct infection by HIV. Although more pronounced abnormalities are seen in patients with advanced HIV disease who are likely to be taking marrow-toxic drugs and in whom OI and malignancies are common, it is emphasized that important BM changes are present in HIV positive patients who at the time of biopsy do not have evidence of infection or neoplastic disease and who have not received treatment for their positive HIV status. The cell line which most frequently shows changes in haematopoesis is the megakaryocytic lineage; of these changes, the presence of increased numbers of naked megakaryocytic nuclei (NMN) are a consistent and specific feature. The finding of BM changes in patients at an early stage of HIV disease points to either the direct effect of HIV infection of BM cells or to abnormal cytokine production or both.