False Homozygosity Results in HLA Genotyping due to Loss of Chromosome 6 in a Patient with Acute Lymphoblastic Leukemia.
10.3343/kjlm.2011.31.4.302
- Author:
Hyewon PARK
1
;
Jungwon HYUN
;
Sung Sup PARK
;
Myoung Hee PARK
;
Eun Young SONG
Author Information
1. Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul Korea. eysong1@snu.ac.kr
- Publication Type:Case Report
- Keywords:
Loss of heterozygosity;
HLA genotyping;
Precursor-B lymphoblastic leukemia
- MeSH:
Adult;
Chromosome Duplication;
*Chromosomes, Human, Pair 6;
Diagnostic Errors;
Female;
Genotype;
HLA Antigens/*genetics;
Hematopoietic Stem Cell Transplantation;
Humans;
Karyotyping;
Leukocyte Count;
*Loss of Heterozygosity;
Nerve Tissue Proteins/genetics;
Precursor Cell Lymphoblastic Leukemia-Lymphoma/diagnosis/*genetics/therapy;
RNA-Binding Proteins/genetics
- From:The Korean Journal of Laboratory Medicine
2011;31(4):302-306
- CountryRepublic of Korea
- Language:English
-
Abstract:
Loss of heterozygosity (LOH) in chromosome 6p has been reported in a number of tumors and some hematologic malignancies, including ALL. LOH in chromosome 6p, on which the HLA genes are located, can give rise to false homozygosity results in HLA genotyping of patients with hematologic malignancies. Here we report false homozygosity results in HLA genotyping due to the loss of whole chromosome 6 in the neoplastic cells of a patient with ALL. A 33-yr-old Korean female patient was admitted for the evaluation of leukocytosis detected during a workup for headache. Her initial white blood cell count was 336.9x109/L with 84% of blasts in the differential count. Precursor-B lymphoblastic leukemia was diagnosed from a subsequent bone marrow study. HLA high-resolution genotyping of the patient was requested at the time of diagnosis for possible hematopoietic stem cell transplantation. Homozygosity results (A*02:01, B*54:01, C*08:01, DQB1*04:01) were obtained, except for the DRB1 locus (DRB1*04:05, DRB1*11:01), in sequence-based typing. Conventional karyotyping of bone marrow metaphase cells revealed chromosomal abnormalities, with loss of multiple chromosomes including chromosome 6, and reduplication of the remaining chromosomes: 29,X,+X,+8,inv(9)(p11q13),+10,+14,+18,+21[15]/58,idemX2[3]/46,XX,inv(9)[2]. LOH at the HLA region was suspected and HLA genotyping was repeated with the peripheral blood in remission state after induction chemotherapy. All 5 HLA loci were typed as heterozygous (A*02:01, A*02:06, B*40:01, B*54:01, C*03:04, C*08:01, DRB1*04:05, DRB1*11:01, DQB1*03:01, DQB1*04:01). To avoid false HLA typing results in patients with hematologic malignancies, clinicians, as well as laboratory personnel, need to be aware of such problems and take appropriate precautions.
