On this page, you will find information about a genetic change that was identified in a UDN participant. We are trying to find others with the same or similar condition.

Sharing information on this website is not a requirement of UDN participation. Only descriptions about participants who give explicit consent will appear here.

A change in the MMACHC gene was identified in a UDN participant with decline in language and memory (cognitive regression), sudden muscle jerks (myoclonus), and increased muscle tone in lower limbs (limb hypertonia)

Date of Report

Mar 20, 2023

Full Name

metabolism of cobalamin associated C

Chromosome 1 (1p34.1)


MMACHC gene is responsible for forming a complex to transport cobalamin across the lysosomal membrane(Deme et al., 2014). Additionally, it assists in the conversion of MeCbl or AdoCbl into intermediate cob(I)alamin (Kim et al., 2009). It is a cobalamin cytosolic chaperone that catalyzes the reductive decyanation of cyanocob(III)alamin to yield cob(II)alamin and cyanide (Kim et al., 2008; Froese et al., 2009; Koutmos et al., 2011; Gherasim et al., 2015).

Database Links

GeneCards: MMACHC

MedlinePlus Genetics: MMACHC

NCBI Gene: 25974

OMIM: 609831

UniProtKB/Swiss-Prot: Q9Y4U1

Clinical Significance

A heterozygous change in this gene was identified in a UDN participant. Research is underway to see if this change is causing symptoms in this participant.

Inheritance Pattern Autosomal recessive
Position (hg19) chr1:g.45973217dup
Transcript NM_015506.3
DNA Change c.271dup
Protein Change p.Arg91LysfsTer14
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