Prevalence of the myelodysplastic syndromes in Japan.

To determine the prevalence of the myelodysplastic syndromes (MDS) in Japan, we conducted a nationwide survey in 1991. The survey included the sex, birth date and type of MDS of the patients from all (n = 2315) hospitals with 200 beds or more and 188 hospitals randomly selected from 7526 hospitals (1/40) with 199 beds or less. The point prevalence of MDS was estimated to be almost 3000 as of September 1, 1991, and it was 3.4 per 100,000 men of 15 years old or older and 2.1 per 100,000 women of 15 years old or older. Refractory anemia (RA) was most common (51%) followed by RA with excess of blasts (RAEB; 18%) and RAEB in transformation (RAEB-t; 14%). RAEB, RAEB-t and chronic myelomonocytic leukemia (CMML) showed a high male/female ratio (3.0 or higher) although the sex ratio of other types was almost 1.0.