Disorders of intracellular cobalamin (Cbl) metabolism are classified from A to J according to biochemical phenotype, and genetic and complementation analyses. CblD-deficient patients present with developmental, hematologic, neurologic, and metabolic findings.
An 11-year-old boy presented with neutropenia, increased mean corpuscular volume, psychomotor retardation, and seizures. His plasma total homocysteine and urinary methylmalonic acid levels were elevated, and a homozygous nonsense mutation [p. R250X (c.748C>T] leading to premature termination of translation was identified in the MMADHC gene, which was compatible with CblD defect.
In the presence of increased mean corpuscular volume and other hematologic manifestations, such as leukopenia, thrombocytopenia, and megaloblastic anemia, with severe nonspecific or mild neurologic symptoms, Cbl synthesis defects should be considered.
*Department of Pediatrics, Division of Pediatric Nutrition and Metabolism
†Division of Pediatric Neurology, Faculty of Medicine, Erciyes University, Kayseri, Turkey
Our case report did not require Ethics Committee Approval, but written consent was obtained from his parents.
The authors declare no conflict of interest.
Reprints: Pembe Soylu Ustkoyuncu, MD, Department of Pediatrics, Division of Pediatric Nutrition and Metabolism, Faculty of Medicine, Erciyes University, Melikgazi, Kayseri 38039, Turkey (e-mail: email@example.com).
Received July 14, 2017
Accepted October 24, 2017