157 Transient Abnormal Myelopoiesis in a Constitutionally Normal 46, XX Newborn Showing Trisomy 21 Mosaicism on Peripheral Blood. (11th January 2018)

• Record Type: Journal Article
• Authors: Murray, Glenn; Klairmont, Matthew
• Is Part Of: American journal of clinical pathology. Volume 149(2018)Supplement 1
• Page Start: S67
• Page End: S67
• Publication Date: 2018-01-11
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqx121.156
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Introduction: Transient abnormal myelopoiesis (TAM) is a disorder that presents clinically and morphologically indistinguishable from acute myeloid leukemia in newborns with Down syndrome. TAM occurs in approximately 10% of Down syndrome newborns and rarely in phenotypically normal neonates showing trisomy 21 mosaicism. We report a unique presentation of TAM in a constitutionally normal 46, XX newborn exhibiting trisomy 21 mosaicism on peripheral blood. Case Study: A 34-week gestation newborn presented with a WBC count of 100k/mm 3 . Eight-color peripheral blood flow cytometry revealed 56% blasts that were positive for CD7, CD34 (minor subset), CD33 (minor subset), CD56, CD117, CD41, and CD42b, consistent with a megakaryoblastic lineage. Peripheral blood karyotype, on presentation, revealed 47, XX+21[44]/46XX[6] mosaicism. FISH performed on the presenting peripheral blood revealed 101 cells with three copies of the21q22.13->22.2 region, consistent with trisomy 21. In addition, 58 cells were found to have four to six copies of the 21q22.13->22.2 region, and 41 cells were found to have two normal copies. After two weeks, the WBC count normalized with no evidence of blasts. Whole blood and saliva CombiSNP Array, one month after birth, revealed a normal female genomic profile with no diagnostic copy number changes. Unfortunately, fetal and placental hydrops fetalis with superimposed Pseudomonas aeruginosa infection of the lungs led to sepsis and patient expiration. Discussion: This is a unique presentation of TAM in a slightly phenotypically dysmorphic 46, XX female patient. This case most likely represents trisomy 21 mosaicism with associated TAM, an uncommon, but well documented presentation. The other less likely possibility is a constitutionally normal 46, XX karyotype with somatic trisomy 21 of the megakaryoblastic cells. The subpopulation of cultured peripheral blood cells showing four to six copies of chromosome 21 could represent a true somatic chromosomal aberration, but polyploidy is not an uncommon finding in cell cultures.