Trisomy 21 mosaicism complicated by refractory cytopenia of childhood

Abstract

A 15-year-old girl was pointed out to have pancytopenia by a nearby doctor, and she was diagnosed as having refractory cytopenia of childhood (RCC) at the age of 5. She was independent from transfusion and had no severe infection or bleeding in her clinical course. She had neither facial abnormality nor deformity, although she was short of stature (–2.4 SD). Consecutive G-banding analysis of bone marrow cells suggested trisomy 21 in some proportion of analyzed cells. Therefore, at the age of 15, interphase FISH analysis of chromosome 21 in buccal smear cells was performed, and she was diagnosed as having mosaicism trisomy 21. The cases of mosaicism trisomy 21 do not necessarily have the typical phenotype of trisomy 21, although there has been no reported case of mosaicism trisomy 21 complicated by RCC. There is a possibility that mosaicism trisomy 21 is undiagnosed in some patients with RCC. Therefore, mosaicism trisomy 21 should be examined in RCC patients with short stature and possible karyotype.