A 16-month-old girl of Spanish origin with chronic hemolytic anemia and severe neuromuscular disease was found to have markedly reduced triosephosphate isomerase (TPI) activity in her erythrocytes, leukocytes, and plateletes.
At least 80 mutations have been identified in the gene encoding the skeletal muscle ryanodine receptor and linked to several neuromuscular disorders, whose common feature appears to be a dysregulation of calcium homeostasis.
The six-minute walk test (6MWT) is an endurance test with high reliability and validity used to measure walking capacity, disease progression, and more recently, fatigability in NMDs with limited results in RYR1-RM.
Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are a common cause of inherited neuromuscular disorders and have been associated with a wide clinical spectrum, ranging from various congenital myopathies to the malignant hyperthermia susceptibility (MHS) trait without any associated weakness.
Within this cohort, mutations were found in eight previously known neuromuscular disease genes (CHRND, CHNRG, ECEL1, GBE1, MTM1, MYH3, NEB and RYR1) and four novel neuromuscular disease genes were identified and have been published as separate reports (GPR126, KLHL40, KLHL41 and SPEG).
Myopathies due to mutations in the skeletal muscle ryanodine receptor (RYR1) gene are amongst the most common non-dystrophic neuromuscular disorders and have been associated with both dominant and recessive inheritance.
Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are a common cause of neuromuscular disease, ranging from various congenital myopathies to the malignant hyperthermia (MH) susceptibility trait without associated weakness.
At least three phenotypes associated with more than 100 RYR1 mutations have been identified; in order to elucidate possible pathophysiological mechanisms of RYR1 mutations linked to neuromuscular disorders, it is essential to define the mutation class by studying the functional properties of channels harbouring clinically relevant amino acid substitutions.
Genetic testing of RYR1 is indicated for all patients with MH, and anaesthetic precautions should be considered for any child with symptoms of neuromuscular disease.
To recognize distinctive proteins underlying affected biochemical pathways, we compared them with fibroblasts from healthy controls and, more importantly, fibroblasts from patients with non-lamin related neuromuscular disorders.
Mutations of the lamin A/C gene are associated with several different neuromuscular diseases, and the detailed effect of disease-associated amino acid substitutions on the structure and stability of human lamin dimers is yet unknown.
Although it is previously known that alterations in the rod domain of type A lamins are involved in cardiac and neuromuscular diseases, our current observation shows that exon 1 LMNA mutations may be associated with partial lipodystrophy without any cardiac and neurological abnormalities, at least at the time of the presentation.
This meta-analysis suggests that cardiomyopathy due to lamin A/C gene mutations portends a high risk of sudden death, and that this risk does not differ between subjects with predominantly cardiac or neuromuscular disease.
Recently, TRPV4 mutation has also been identified in a spectrum of neuromuscular diseases that includes congenital distal spinal muscular atrophy (SMA), scapuloperoneal SMA, and hereditary motor and sensory neuropathy type IIC.
In light of previously well described dominant inheritance for TRPV4-related neuromuscular disease, our study suggests a role for compound heterozygosity and loss-of-function as a potential novel disease mechanism for this group of disorders.