So far, all mutations are located within the exons, and are either missense, nonsense or frameshift mutations. Splice site mutations have not so far been observed. The mutations are located across several regions of the protein. The most severe reported phenotypes, especially with relation to psychomotor and speech delay, were associated with homozygous mutations towards the N-terminal part of the protein. A phenotype-genotype correlation is not well defined and severity of the phenotype might depend on modifying factors, or the presence of homozygous variants rather than compound heterozygous
TMTC3