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Letter to the Editor
37 (
2
); 63-64
doi:
10.25259/KPJ_27_2022

Nutritional Vitamin-B12 deficiency masquerading as a mitochondrial disorder

Department of Paediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
Corresponding author: Vykuntaraju K. Gowda, Department of Paediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India. drknvraju08@gmail.com
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This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Gowda VK, Chauhan S, Srinivasan VM. Nutritional Vitamin-B12 deficiency masquerading as a mitochondrial disorder. Karnataka Paediatr J 2022;37:63-4.

Dear Editor,

Secondary mitochondrial dysfunction is known to occur in cobalamin deficiency.[1] Here, we report Vitamin-B12 deficiency masquerading as mitochondrial disease. An 11-month-old boy presented with decreased activity for 3 weeks, fever for 1 week, tachypnoea and refusal of feeds for the past 1 day. The child was on a predominantly breastfed diet. The child lost his attained milestones of sitting and recognition of parents for the past 3 weeks.

On examination, the child was drowsy, heart rate of 130/min, respiratory rate of 60/min, weight (9 kg), length (74 cm) and head circumference (46 cm) was normal. He had pallor, knuckle hyperpigmentation, hypopigmented sparse hair, lethargy, hypotonia, power 3/5 in all four limbs, gallop rhythm and hepatomegaly. On investigations, haemoglobin was low 2.4 g/dL, total leukocyte counts 18,300 cells and low platelet count 16,000 with high mean corpuscular volume (104 fL), high lactate 16.65 mg/dL, low Vitamin-B12 <50 pg/mL and high homocysteine levels 36.5 umol/L. Peripheral smear and bone marrow showed features of the megaloblastic picture. Arterial blood gas was suggestive of high anion gap severe metabolic acidosis (pH: 6.898, Pco2: 12 and pHCO3–: 2.3 mmol/L with base excess: 29.4). MRI brain was suggestive of cerebral atrophy. TMS was suggestive of high alanine 1105.12 (74–613) with an elevated glutamate/ lysine ratio of 982.67 (211–683). Whole exome and mitochondrial genome sequencing were not shown any variants. Treated with supportive care, injection vitamin-B12, and packed red blood cell transfusion. After 14 days, the haemoglobin improved to 10.2 g/dL, TMS and pH normalised.

The above changes are probably due to elevated MMA in Vitamin-B12 deficiency which leads to inhibition of carbamoyl phosphate synthetase I, pyruvate carboxylase and the dicarboxylate carrier needed for malate shuttle.[2] Hence, Vitamin-B12 deficiency is to be considered in differentials when features are suggestive of mitochondrial disorders.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

  1. , , , , , , et al. Accumulation of methylmalonic acid caused by Vitamin B12-deficiency disrupts normal cellular metabolism in rat liver. Br J Nutr. 1996;75:929-38.
    [CrossRef] [PubMed] [Google Scholar]
  2. . Methylmalonic acidemia (MMA) Mol Genet Metab. 2005;85:2-6.
    [Google Scholar]

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