MK-8669 br Introduction Aplastic anemia AA is a rare disease

Introduction Aplastic anemia (AA) is a rare disease characterized by pancytopenia and a hypocellular bone marrow. Specific cytogenetic abnormalities, monosomy 7 and trisomy 8, are frequently associated with clonal evolution [1]. Clonal cytogenetic abnormalities also may be present with hypocellular bone marrow morphology: some experts have used them to differentiate AA from hypoplastic myelodysplastic syndrome (MDS) [2], while others accept certain aberrations as consistent with AA [3]. Although cryptic RUNX1/AML1 lesions have been reported in patients with Fanconi anemia and MDS [4], the (8;21) translocation is not observed by standard cytogenetic methods in bone marrow failure diseases.
Case report A 23-year-old Ecuadorian homemaker, resident in the United States, presented to medical attention with a peritonsillar abscess. Laboratory studies at presentation showed white blood MK-8669 1.38k/μL, absolute neutrophil count 0k/μL, hemoglobin 7.4g/dL, absolute reticulocyte count 5k/μL, and platelets 38k/μL. Initial bone marrow biopsy revealed 5% cellularity with minimal trilineage hematopoiesis. Cytogenetics showed normal female karyotype 46,XX in all 20 analyzed metaphases. She was referred to the National Institutes of Health (NIH) for evaluation and consideration for immunosuppressive therapy (IST) and eltrombopag on a clinical trial (NCT01623167). There was no evidence of an inherited bone marrow failure disorder on physical examination or from a detailed family history. Tests for Fanconi anemia (diepoxybutane stress) and telomere disorders (leukocyte telomere length) were normal. Flow cytometric evaluation for paroxysmal nocturnal hemoglobinuria (PNH) was negative. Repeat bone marrow analysis performed immediately prior to IST (as required by protocol) demonstrated 10% cellularity, no dysplasia, nor increased number of blasts. Less than 1% of cells were CD34 positive. Severity of neutropenia (ANC<200/μL) prompted immediate treatment on protocol, beginning with equine antithymocyte globulin (ATG) and cyclosporine, standard for severe AA. However, two days after completion of IST, standard cytogenetic analysis returned t(8;21)(q22;q22) in 3 out of 20 metaphases, with confirmation by FISH (Fig. 1A). The patient was placed “off protocol” and did not receive the study drug, eltrombopag. This significant cytogenetic abnormality was unexpected and was inconsistent with the marrow morphology. Three months after initial presentation at NIH, confirmatory bone marrow evaluation showed 2/2 metaphases with t(8;21) abnormality. Focally increased CD34+ cells were observed by IHC (Fig. 1B, C) but not by flow cytometry. Her clinical status was unchanged after receiving IST: she remained severely pancytopenic and transfusion-dependent. Chemotherapy for AML was withheld due to the severe pancytopenia, hypocellularity, and absence of increased blasts. Progression to frank leukemia with circulating blasts did not occur until eight months following initial presentation. She underwent allogeneic stem cell transplantation from a matched sibling donor. She had minimal grade chronic GVHD of the skin, that was successfully treated with steroids. Eight months after successful bone marrow transplant, the patient is in remission. The core binding factor leukemia involving translocation of 8;21 (q22;q22), generating a fusion of RUNX1 and AML1 genes, is considered leukemia-defining, regardless of the number of blasts [5]. This unusual case prompted us to perform comparative genomic hybridization (CGH). Single nucleotide polymorphism (SNP) based CytoScan high-density microarray [6] was performed on DNA derived from the patient׳s bone marrow cells. Sample obtained at NIH at initial diagnosis had no identifiable gains or losses of more than 100,000bp. However, multiple, large regions of copy neutral loss of heterozygosity (LOH, also referred to as uniparental disomy) were identified, ranging in size from 3 to 29Mbp on multiple chromosomes. CGH did not demonstrate any large regions of copy neutral LOH in 10 patients with acquired severe AA with normal cytogenetics, nor in 35 healthy controls. Emerging data show that SNP arrays can detect abundant copy neutral LOH amongst select hematologic malignancies and are associated with the duplication of oncogenic mutations [7]. Addition of SNP arrays to standard cytogenetics increases the ability to identify a clonal marker from 50% to 80% [6]. When we compared locations of LOH in our patient with reported genes involved in evolution of mutations in AML we found several important overlaps (Table 1). These results suggest SNP based CGH arrays may be useful in distinguishing hypocellular AML from AA.