A decade has passed since transmembrane coiled-coil domains 1 (TMCO1) defect syndrome was identified in 11 undiagnosed patients within the Old Order Amish of Northeastern Ohio-a disorder characterized by a distinctive craniofacial dysmorphism, skeletal anomalies and global developmental delay. Twenty seven patients, from diverse ethnic groups, have been reported with pathogenic TMCO1 variants now recognized to cause cerebrofaciothoracic dysplasia (CFTD). The implication of previously uncharacterized TMCO1 within disease has instigated a 10-year journey to understand the function of TMCO1 protein in Ca2+ homeostasis. TMCO1 is an ER Ca2+ leak channel which facilitates Ca2+ leak upon ER \"overload\" through the novel Ca2+ load activated Ca2+ mechanism. This mini-review brings together the clinical and scientific advances made since the discovery of TMCO1 deficiency in disease, including broadened phenotype, understanding of pathophysiology, and implications to patient management of TMCO1 defect syndrome.

Congenital fiber type disproportion (CFTD) is a rare congenital myopathy subtype defined by slow type 1 hypotrophy in the absence of any other major structural findings such as rods, central nuclei or cores. Dominant missense changes in slow alpha-tropomyosin coded by TPM3 gene are the main cause of the CFTD. There are only a few reports of recessive loss-of-function mutations in TPM3 causing severe Nemaline Myopathy and CFTD. We present two patients harboring TPM3 mutations. The first is a novel homozygous missense variant with a mild CFTD clinical phenotype inherited in a recessive fashion. The second is a previously reported heterozygous mutation presenting within pronounced early axial involvement and dropped head. This report expands the genotype-phenotype correlation in the TPM3 myopathy showing a recessive mutation causing a mild clinical phenotype and also shows that TPM3 mutations should be part of the investigation in patients with dropped head.

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BACKGROUND: Pathogenic variants in ryanodine receptor 1 (RYR1, MIM# 180901) are the cause of congenital myopathy with fiber-type disproportion, malignant hyperthermia susceptibility type 1, central core disease of muscle, multiminicore disease and other congenital myopathies.
METHODS: We present a patient with global developmental delay, hypotonia, myopathy, joint hypermobility, and multiple other systemic complaints that were noted early in life. Later she was found to have multiple bone deformities involving her spine, with severe scoliosis that was corrected surgically. She was also diagnosed with ophthalmoplegia, chronic hypercapnic respiratory failure, and hypertension. At 22 years of age she presented to the genetics clinic with a diagnosis of mitochondrial myopathy and underwent whole exome sequencing (WES).
RESULTS: Whole exome sequencing revealed two novel compound heterozygous variants in RYR1 (c.7060_7062del, p.Val2354del and c.4485_4500del, p.Tyr1495X).
CONCLUSIONS: Review of her clinical, pathologic, and genetic findings pointed to a diagnosis of a congenital myopathy with fiber-type disproportion.

A boy, who had shown muscle weakness and hypotonia from early childhood and fiber type disproportion (FTD) with no dystrophic changes on muscle biopsy, was initially diagnosed as having congenital fiber type disproportion (CFTD). Subsequently, he developed cardiac conduction blocks. We reconsidered the diagnosis as possible LMNA-myopathy and found a heterozygous mutation in the LMNA gene. This encouraged us to search for LMNA mutations on 80 patients who met the diagnostic criteria of CFTD with unknown cause. Two patients including the above index case had heterozygous in-frame deletion mutations of c.367_369delAAG and c.99_101delGGA in LMNA, respectively. Four of 23 muscular dystrophy patients with LMNA mutation also showed fiber type disproportion (FTD). Importantly, all FTD associated with LMNA-myopathy were caused by hypertrophy of type 2 fibers as compared with age-matched controls, whereas CFTD with mutations in ACTA1 or TPM3 showed selective type 1 fiber atrophy but no type 2 fiber hypertrophy. Although FTD is not a constant pathological feature of LMNA-myopathy, we should consider the possibility of LMNA-myopathy whenever a diagnosis of CFTD is made and take steps to prevent cardiac insufficiency.