Thiamine-responsive megaloblastic anemia syndrome: A case report

Abstract

Thiamine-responsive megaloblastic anemia (TRMA) syndrome is a rare autosomal recessive disorder characterized by a cardinal triad consisting of megaloblastic anemia, sensorineural deafness, and diabetes mellitus. TRMA is caused by mutations in the gene SLC19A2 encoding a high-affinity thiamine transporter, which disturbs the active thiamine uptake into cells. We report here on a 1-year and 9-month-old female baby with megaloblastic anemia, thrombocytopenia, and diabetes mellitus. Our patient had significant sensorineural hearing loss that was late to appear. Diagnosis was based on clinical features and dramatic response of anemia,thrombocytopenia, and glycemic control to thiamine therapy. In view of the clinical history of the patient, targeted gene sequencing of genes causing monogenic diabetes was performed. The genes selected comprised 40 gene loci and were sequenced by Illumina sequencing platform. We found a novel homozygous deletion mutation of complete exon 2 of the SLC19A2 gene (ENST00000236137),which we believe has not been described to be associated with TRMA. Exon 2 of SLC19A2 gene includes amino acid from 69 to 269. Thiamine resulted in rapid normalization of the hemoglobin level with improvement in glycemic control. TRMA syndrome should be kept in mind in the differential diagnosis of megaloblastic anemia, deafness, and diabetes mellitus. Early introduction of high-dose thiamine can reverse anemia and allow more glycemic control for diabetes. We conclude that genetic analysis confirms the diagnosis of TRMA. As exogenous thiamine is shown to reverse some of the clinical features of the disease, a genetic diagnosis of TRMA syndrome is extremely important.