ABSTRACT
I. INCIDENCE A. Difficulties in Establishing the True Incidence The true incidence of the myelodysplastic syndromes (MDS) is not known. Because these syndromes have been recognized only recently, the International Classification of Diseases (ICD), 9th edition (1) did not identify them as nosological entities and therefore they tended to get lost under a disparate variety of headings. Chronic myelomonocytic leukemia (CMML), for example, was included in ICD-9, but only as a type of chronic myeloid leukemia. Furthermore, the term ‘‘myelodysplasia’’ in the ICD-9 manual refers to congenital defects of the spinal canal. The more specialized diagnostic manual, the International Classification of Disease for Oncology, suffers from the same defect, and thus it is that cancer registries, death certification, and hospital discharge data are of little value in establishing the prevalence of myelodysplastic syndromes. Indeed, the nonuniform classification scheme for MDS is exemplified by a Swedish study that found myelodysplastic syndromes recorded in Cancer Registries under five different diagnoses (2).
