Abstract
Myelodysplastic syndrome (MDS) is rare in children. Certain inherited bone marrow failure syndromes (IBMFS), such as Fanconi anemia, severe congenital neutropenia and Shwachman Diamond syndrome, markedly increase the risk of MDS during childhood. However, the genetic factor(s) underlying sporadic pediatric MDS are unknown. Germline mutations in GATA2, a hematopoietic transcription factor, explain four MDS-predisposing conditions: monocytopenia and mycobacterial infection (MonoMAC); dendritic cell, monocyte, B and NK cell lymphoid deficiency (DCML); primary lymphedema with myelodysplasia progressing to acute myeloid leukemia (Emberger syndrome); and a subset of familial MDS. Cases of pediatric MDS have been observed in some of the reported pedigrees. In addition, three individuals have been reported with large, de novo deletions encompassing GATA2 and surrounding genes and manifesting developmental delay, intellectual disability and dysmorphic features alongside their hematologic abnormalities. We identified a novel GATA2 splice site variant (c.1018-2A>C) in a teenager with MDS, WHO classification refractory cytopenia of childhood (RCC). Although he was found to have monocytopenia and B and NK cell deficiencies, he had no history of infections associated with MonoMAC or pertinent family history. We, therefore, hypothesized that mutations in GATA2 might be present in additional cases of pediatric MDS that were neither associated with an IBMFS nor relevant personal or family history.
Two Baylor College of Medicine biology studies open to children with hematologic disease were queried for patients with the diagnosis of MDS. Exclusion criteria included treatment-related MDS, diagnosis of an IBMFS, prior diagnosis of severe aplastic anemia or infections suspicious for MonoMAC or DCML, and known or suspected family history of a GATA2-associated disorder. Cases lacking a pre-hematopoietic stem cell transplantation (HSCT) tissue sample available for study were also excluded. In addition to the patient described above, six children were identified who met eligibility criteria. DNA was isolated from banked peripheral blood or bone marrow cells and GATA2 sequencing performed, including upstream and intronic regulatory regions. Array comparative genomic hybridization was also performed on one sample that lacked GATA2 sequence variants, but was notable for complete absence of heterozygosity (AOH), including 6 polymorphic sites with minor allele frequencies of 0.20 or greater. Pertinent clinical and laboratory features were extracted by medical record review blinded to GATA2 status.
We found heterozygous GATA2 mutations in three of the six additional patient samples. Thus, four of this seven patient, pediatric MDS cohort had mutated GATA2. Two of the newly identified mutations were splice site variants: a previously described c.1018-1G>A and a novel variant altering the exon 7 splice site acceptor (c.1114-1G>C). The third mutation was a de novo 3.1-3.3 Mb deletion encompassing the entire GATA2 locus and contiguous genes, and was established to be germline by analysis of skin fibroblasts. Notably, the patient had normal neurocognitive development and was without dysmorphic features. Their ages of presentation were 5, 9, 12 and 15 years. With the exception of the initial case, peripheral blood T and B cell phenotyping was not obtained prior to HSCT. Monocytopenia of less than 200/µL was present in five of seven patients, three of whom had a GATA2 mutation. All four GATA2 mutation cases had RCC and three of the four had monosomy 7 at diagnosis. In contrast, the three cases lacking GATA2 mutation presented with the MDS classification refractory anemia with excess blasts (RAEB-2), with either a normal karyotype, complex karyotypic changes or chromosome 13.q12q14 deletion.
GATA2 mutation may explain a significant portion of sporadic, seemingly nonsyndromic pediatric MDS, particularly cases with monosomy 7. Evaluation of larger cohorts is warranted to ascertain the true prevalence. Although this cohort is small, we recommend GATA2 sequencing be performed as part of the initial evaluation of pediatric MDS as the identification of a germline mutation has critical implications for related donor selection and genetic counseling. AOH in GATA2 sequencing should prompt deletion analysis, even in cases without infections, dysmorphic features or neurocognitive impairment.
Disclosures:
No relevant conflicts of interest to declare.
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