A teenager with combined methylmalonic aciduria and homocystinuria (CblC type) presenting with neurological symptoms and congenital heart diseases: a case report

ABSTRACT

Combined methylmalonic acidemia and homocystinuria, is a rare autosomal recessive disorder due to defective intracellular cobalamin metabolism. We report an 18-year-old Chinese male who presented with hypermyotonia, seizures, and congenital heart diseases. Mutation analysis revealed c.365A>T and c.482 G>A mutations in the MMACHC gene, diagnosed with methylmalonic aciduria and homocystinuria (CblC type). After treatment with vitamin B₁₂, L-carnitine, betaine, and folate, which resulted in an improvement in his clinical symptoms and laboratory values. This case emphasizes that inborn errors of metabolism should be considered for a teenager presenting with challenging or neurologic symptoms, especially when combined with unexplained heart diseases.

KEYWORDS:

• Cobalamin C deficiency
• MMACHC
• methylmalonic aciduria
• homocysteinemia
• late-onset

Acknowledgments

We are very grateful to the patients and their families for their cooperation.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

This study complied with the guidelines for human studies and was conducted in accordance with the World Medical Association Declaration of Helsinki. Written consent was obtained from the family to publish this case (including publication of images). The authors confirm that the data supporting the findings of this study are available within the article.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China to Qin Yan [81671309 and 81971229].