Histopathology of the bone marrow in toxic myelopathy. A study of drug induced lesions in 57 patients.

Following the introduction of numerous highly effective drugs in recent decades, haematologists are confronted with a panmyelopathy or "toxic myelopathy" originating from the exhibition of certain therapeutic regimens. Among 16,711 trephines referred to us in the last 5 1/2 years, 57 cases or 0.34 percent were found to have clear evidence of lesions caused by the ingestion of potentially toxic agents. The evaluation of the histopathology shows two groups of alterations which concern the haematopoietic parenchyma as well as the mesenchyme of the bone marrow. Different degrees of cellularity ranging from aplasia to regenerative hyperplasia and a pronounced mesenchymal reaction with proteinaceous oedema, perivascular plasmacytosis and frequent necrobiosis of neutrophilic granulocytes or cellular debris are the most conspicuous features. However, the histopathology of the bone marrow described gives no indication of the specific drug responsible and no specific suggestion of any group of drugs. Generally the histopathology allows the recognition of lesions which are induced by the toxicity of these agents. Therefore a bone marrow biopsy should be included in the diagnostic procedures whenever a toxic lesion is suspected of causing haematological disorders, particularly in all cases of uncertain pancytopenia.