Usefulness of Buccal Smears in Rapid Diagnosis of Congenetial Myeloproliferative Disorders. K. Patel, S. White, P. Hsu, J. Jacob, R. Kazi, AL. Zaslav. Department of Laboratory Medicine, Long Island Jewish Medical Center,the Long Island Campus of the Albert Einstein College of Medicine, New Hyde Park, NY 11040.
   Neonatal myeloproliferative disorders (NMD) can represent a benign transient myeloproliferative disorder (TMD) associated with trisomy 21 Down syndrome (DS) or acute myeloid leukemia (AML) requiring aggressive management. It is important to identify true trisomy 21 so that these neonates can be treated conservatively. In NMD, the presence of trisomy 21 in peripheral blood may represent an acquired chromosome abnormality, which indicates secondary AML. Another tissue must be cytogenetically evaluated to determine this. We report two cases of NMD, in which trisomy 21 was first seen in peripheral blood. The clinical dilemma was resolved by rapidly identifying inherited trisomy 21 in epithelial nuclei from a buccal smear (BS) using FISH.
   Two neonates without obvious DS phenotype or previously documented DS genotype presented with leukemic peripheral blood smears. Twenty trypsin-Giemsa banded metaphase spreads from peripheral blood revealed trisomy 21 in both cases. Fluorescent in situ hybridization (FISH) was performed on BS nuclei and peripheral blood cells using Aneu Vysion LSI 13/21 probe (Vysis, Downers Grove, ILL). In both the cases, the FISH analysis on interphase nuclei from blood and BS showed three signals for chromosome 21 in all cells indicating inherited trisomy 21. Based on the FISH results, the increased WBC count and blasts in the peripheral smear, the patients were diagnosed with DS-associated TMD and were managed conservatively. One of the two neonates showed resolution of myeloproliferative symptoms after four months of age and is disease-free one year after the initial diagnosis. The other expired at three months of age due to congenital heart defects.
   This report demonstrates the use of BS in conjunction with FISH as an additional tissue to provide a quick method of determining acquired vs. inherited chromosome abnormalities. This technique was essential in assisting the clinicians with efficient, rapid, and accurate management of these cases.