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 336.9×10(9)/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.

Carbapenem-resistant Klebsiella pneumoniae isolates producing K. pneumoniae carbapenemases (KPC) were first reported in the USA in 2001, and since then, this infection has been reported in Europe, Israel, South America, and China. In Korea, the first KPC-2-producing K. pneumoniae sequence type (ST) 11 strain was detected in 2010. We report the case of a patient with a urinary tract infection caused by KPC-2-producing K. pneumoniae. This is the second report of a KPC-2-producing K. pneumoniae infection in Korea, but the multilocus sequence type was ST258. The KPC-2-producing isolate was resistant to all tested β-lactams (including imipenem and meropenem), amikacin, tobramycin, ciprofloxacin, levofloxacin, and trimethoprim-sulfamethoxazole, but was susceptible to gentamicin, colistin, polymyxin B, and tigecycline. The KPC-2-producing isolate was negative to phenotypic extended-spectrum β-lactamase (ESBL) and AmpC detection tests and positive to modified Hodge test and carbapenemase inhibition test with aminophenylboronic acid.

Alpha 1-antitrypsin (AAT) deficiency is a genetic disorder that primarily affects the lungs and liver. While AAT deficiency is one of the most common genetic disorders in the Caucasian population, it is extremely rare in Asians. Here, we report the case of a 36-year-old Korean woman with AAT deficiency who visited the emergency department of our hospital for the treatment of progressive dyspnea that had begun 10 years ago. She had never smoked. Chest computed tomography revealed panlobular emphysema in both lungs, which suggested AAT deficiency. The serum AAT level was 33 mg/dL (reference interval: 90-200 mg/dL). Four exons of the SERPINA1 gene, which is responsible for AAT deficiency, and their flanking regions were analyzed by PCR-direct sequencing. The patient was found to have 1 missense mutation (c.230C>T, p.Ser77Phe; S(iiyama)) and 1 frameshift mutation (c.1158dupC, p.Glu387ArgfsX14; QO(clayton)). This is the first Korean case of AAT deficiency confirmed by genetic analysis and the second case of a compound heterozygote of S(iiyama) and QO(clayton), the first case of which was reported from Japan.

Factor XI (FXI) deficiency is a rare autosomal recessive coagulation disorder most commonly found in Ashkenazi and Iraqi Jews, but it is also found in other ethnic groups. It is a trauma or surgery-related bleeding disorder, but spontaneous bleeding is rarely seen. The clinical manifestation of bleeding in FXI deficiency cases is variable and seems to poorly correlate with plasma FXI levels. The molecular pathology of FXI deficiency is mutation in the F11 gene on the chromosome band 4q35. We report a novel mutation of the F11 gene in an 18-year-old asymptomatic Korean woman with mild FXI deficiency. Pre-operative laboratory screen tests for lipoma on her back revealed slightly prolonged activated partial thromboplastin time (45.2 sec; reference range, 23.2-39.4 sec). Her FXI activity (35%) was slightly lower than the normal FXI activity (reference range, 50-150%). Direct sequence analysis of the F11 gene revealed a heterozygous A to G substitution in nucleotide 1517 (c.1517A>G) of exon 13, resulting in the substitution of aspartic acid with glycine in codon 506 (p.Asp506Gly). To the best of our knowledge, the Asp506Gly is a novel missense mutation, and this is the first genetically confirmed case of mild FXI deficiency in Korea.

We report a rare case of multiple myeloma with biclonal gammopathy (IgG kappa and IgA lambda type) in a 58-year-old man with prostate cancer who presented with lower back pain. Through computed tomography (CT) imaging, an osteolytic lesion at the L3 vertebra and an enhancing lesion of the prostate gland with multiple lymphadenopathies were found. In the whole body positron emission tomography-computed tomography (PET-CT), an additional osteoblastic bone lesion was found in the left ischial bone. A prostate biopsy was performed, and adenocarcinoma was confirmed. Decompression surgery of the L3 vertebra was conducted, and the pathologic result indicated that the lesion was a plasma cell neoplasm. Immunofixation electrophoresis showed the presence of biclonal gammopathy (IgG kappa and IgA lambda). Bone marrow plasma cells (CD138 positive cells) comprised 7.2% of nucleated cells and showed kappa positivity. We started radiation therapy for the L3 vertebra lesion, with a total dose of 3,940 cGy, and androgen deprivation therapy as treatment for the prostate cancer.

Tuberculosis remains a severe public health problem worldwide. Presently, genotyping is used for conducting epidemiologic and clinical studies on tuberculosis cases. We evaluated the efficacy of the repetitive sequence-based PCR (rep-PCR)-based DiversiLab™ system (bioMérieux, France) over the IS6110-restriction fragment length polymorphism analysis for detecting Mycobacterium tuberculosis. In all, 89 clinical M. tuberculosis isolates collected nationwide from Korea were used. The DiversiLab system allocated the 89 isolates to 8 groups with 1 unique isolate when a similarity level of 95% was applied. Seventy-six isolates of the Beijing family and 13 isolates of non-Beijing family strains were irregularly distributed regardless of rep-PCR groups. The DiversiLab system generated a rapid, sensitive, and standardized result. It can be used to conduct molecular epidemiologic studies to identify clinical M. tuberculosis isolates in Korea.

The aminoglycoside 6'-N-acetyltransferases of type Ib (aac(6')-Ib) gene confers resistance to amikacin, tobramycin, kanamycin, and netilmicin but not gentamicin. However, some isolates harboring this gene show reduced susceptibility to amikacin. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends a revision of the phenotypic description for isolates harboring the aac(6')-Ib gene. In this study, we determined the aminoglycoside susceptibility profiles of 58 AAC(6')-Ib-producing Enterobacter cloacae isolates. On the basis of the CLSI and EUCAST breakpoints, a large proportion (84.5% and 55.2%, respectively) of these 58 isolates were found to be susceptible to amikacin. However, among the isolates that were shown to be anikacin-susceptible according to the CLSI and EUCAST breakpoints, only 30.6% and 18.8% isolates, respectively, could be considered to have intermediate resistance on the basis of the EUCAST expert rules. Further studies should be conducted to determine the aminoglycoside susceptibility profiles of aac(6')-Ib-harboring isolates from various geographic regions and to monitor the therapeutic efficacy of amikacin in infections caused by these isolates.