Heterozygous Mutations in Both the AMN and CBS Genes: Double Haploinsufficiency as an Unusual Cause of Vitamin B₁₂ Deficiency—A Case Report

ABSTRACT

Vitamin B₁₂ deficiency is usually simple to diagnose. However, our patient demonstrates that in difficult cases, the ordinary clinician may need a transdisciplinary approach. The finding of a double haploinsufficiency as a possible cause of vitamin B₁₂ deficiency in our patient, illustrates the usefulness of performing large panel clinical exome sequencing.