[The myelodysplastic syndrome I. Pathogenesis, clinical symptoms, diagnosis and differential diagnosis]

The myelodysplastic (MDS) syndrome is characterized by variable cytopenia, owing to bone marrow insufficiency. Known provoking factors for the disease are chemicals (benzene), previous treatment with alkylating agents, and radioactive irradiation. The pathogenesis involves an acquired lesion of the pluripotent haematopoietic stem cell with the evolution of a (pre-)malignant cell clone with an increased proliferation potential, but, in addition, severe dysplasia with ineffective haematopoiesis. An increased intramedullary production of various cytokines that inhibit haematopoiesis, including tumour necrosis factor alpha (TNF-alpha), may be responsible for the accelerated cell death (apoptosis). An increasing genetic instability during the course of the disease causes progression of the cytopenia with anaemia, infections, and bleeding. Autoimmune diseases may be seen. The disease often progresses to acute myeloid leukaemia. A chromosomal analysis is important, as 40-50% of the patients have chromosomal changes at the time of diagnosis. Differential diagnostic considerations include temporary dysplasia provoked by medical or toxic agents, B12 or folate deficiency, infectious bone marrow involvement (HIV, CMV infection), chronic alcoholism, aplastic anaemia, and myelofibrosis.