Metabolic mimic of inherited bone marrow failure: LMBRD1 (cblF) deficiency in an infant.
Aditi Tulsiyan, Sudipto Bhattacharya, Anuj Singh et al.
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Case in brief
An eight-month-old boy presented with macrocytic anemia, reticulocytopenia, neutropenia, infections, failure to thrive, and developmental delay. Bone marrow examination showed hypocellularity, reduced myeloid precursors, dysplastic megakaryocytes, fibrosis, and vacuolated hematopoietic precursors, raising concern for inherited marrow failure. Whole-exome sequencing identified a homozygous LMBRD1 variant, c.907C > A (p.Pro303Thr), with parental segregation confirming the finding. The diagnosis was cblF deficiency, an intracellular cobalamin-metabolism disorder. Parenteral hydroxocobalamin treatment led to partial improvement.
What made this case unusual
The marrow abnormalities mimicked inherited bone marrow failure, but the underlying LMBRD1-related cblF deficiency was treatable; cytoplasmic vacuolization of hematopoietic precursors was among the reported findings.
Diagnostic / clinical pearl
In an infant with cytopenias and marrow findings suggestive of inherited failure, consider intracellular cobalamin-metabolism disorders, including LMBRD1-related cblF deficiency, because they may be treatable.