CONFIRMING FALSE HOMOZYGOSITY INPRE-TRANSPLANT HLA TESTING

Abstract

The HLA gene complex is located on chromosome 6p, and this article examines a patient with acute myeloid leukemia (AML) who has the incorrect HLA homozygosity due to loss of heterozygosity (LOH). Successful hematopoietic stem cell transplant matching relies on precise HLA compatibility testing. Confusion in clinical conditions could arise if LOH is not detected. Oral swabs and peripheral blood samples were used for HLA molecular typing using methodologies such as sequence-based approaches, next-generation sequencing technologies, and chromosomal microarray analysis (CMA). After a bone marrow exam, it was determined that a 68-year-old man suffering from low platelets and anemia had acute myeloid leukemia (AML). Although the karyotype was normal, the blast crisis HLA testing of peripheral blood revealed that all three HLA loci—A, -B, and -C—were likely homozygous (46, XY[20]). Additional testing confirmed the previous results. Heterozygosity at each locus was determined by HLA typing using DNA from oral swabs. Afterwards, a substantial copy-neutral LOH region spanning from 6p25.3 to 6p21.1 and measuring approximately 43.5 Mb in length was discovered by CMA. By providing a reason for the divergent outcomes, this demonstrated the significance of checking for unexpected homozygosity in non-hematopoietic organs.