Dominant missense variants in MYBPC1 encoding slow Myosin Binding Protein-C (sMyBP-C) have been increasingly linked to arthrogryposis syndromes and congenital myopathy with tremor. Herein, we describe novel compound heterozygous variants - NM_002465.4:[c.2486_2492del];[c.2663A > G] - present in fibronectin-III (Fn-III) C7 and immunoglobulin (Ig) C8 domains, respectively, manifesting as severe, early-onset distal arthrogryposis type-1, with the carrier requiring intensive care and several surgical interventions at an early age. Computational modeling predicts that the c.2486_2492del p.(Lys829IlefsTer7) variant destabilizes the structure of the Fn-III C7 domain, while the c.2663A > G p.(Asp888Gly) variant causes minimal structural alterations in the Ig C8 domain. Although the parents of the proband are heterozygous carriers for a single variant, they exhibit no musculoskeletal defects, suggesting a complex interplay between the two mutant alleles underlying this disorder. As emerging novel variants in MYBPC1 are shown to be causatively associated with musculoskeletal disease, it becomes clear that MYBPC1 should be included in relevant genetic screenings.

The main objective of this case report is to identify a gene associated with a Japanese family with autosomal dominant arthrogryposis. We performed clinicopathologic diagnosis and genomic analysis using trio-based exome sequencing. A 14-year-old boy had contractures in the proximal joints, and the serum creatine kinase level was elevated. Muscle biopsy demonstrated a moth-eaten appearance in some type 1 fibers, and electron microscopic analysis revealed that type 1 fibers had Z disk streaming. We identified a heterozygous nonsense variant, c.523A>T (p.K175*), in TNNI1 in the family. The altered amino acid residue is within the tropomyosin-binding site near the C-terminus, in a region homologous to the variational hotspot of Troponin I2 (TNNI2), which is associated with distal arthrogryposis type 1 and 2b. Compared with patients with TNNI2 variants, our patient had a milder phenotype and proximal arthrogryposis. We report here a case of proximal arthrogryposis associated with a TNNI1 nonsense variant, which expands the genetic and clinical spectrum of this disease. Further functional and genetic studies are required to clarify the role of TNNI1 in the disease.

Freeman-Burian syndrome (FBS) is a rare congenital myopathic craniofacial syndrome. Since publication of the genotype-correlated clinical diagnostic criteria, no complete survey of the literature has been accomplished. As part of the clinical practice guideline development, we evaluate diagnostic accuracy for FBS from 1938 to 2019 and range of findings, complications, treatments, and outcomes. Published manuscripts in PubMed, Google Scholar, and OMIM describing cases with a reported diagnosis of FBS, Sheldon-Hall syndrome, and distal arthrogryposes type 1 and 3 are initially included. Articles with sufficient case-level data for diagnosis verification are analyzed further. Of 724 unique papers considered, 188 papers describing 304 unique patients are included; 101 papers and 119 patients reflect an FBS diagnosis, with 80 patients meeting the full diagnostic criteria. Most cases are re-screened as distal arthrogryposis type 1. Among all cases re-screened as FBS, the presence of FBS pathognomonic craniofacial findings is not correlated with other physical findings. There are no significant differences between patients meeting the full diagnostic criteria and those not, but both are distinct from other diagnoses. Plastic surgery demonstrates the highest cumulative diagnostic accuracy for FBS overall (86.66%), while orthopedic surgery shows the lowest (44.83%). No statistically usable treatment-related or psychosocial data are available. Quality of case reports and patient data vary widely, reducing the statistical strength and significance. Major knowledge gaps exist in treatment, psychosocial, and longitudinal outcomes. At this point, it is impossible to derive clinical practice guidelines exclusively from the literature.

Freeman-Sheldon and Sheldon-Hall syndromes (FSS and SHS) and distal arthrogryposis types 1 and 3 (DA1 and DA3) are rare, often confused, congenital syndromes. Few studies exist. With reported diagnosis unreliable, it would be scientifically inappropriate to consider articles describing FSS, SHS, DA1, or DA3, unless diagnoses were independently verified, rendering conventional systematic review and meta-analysis methodology inappropriate and necessitating patient-level data analysis (PROSPERO: CRD42015024740). As part of a clinical practise guideline development process, we evaluate (1) diagnostic accuracy from 1938-2017, using the Stevenson criteria; (2) the most common physical findings, possible frequency clusters, and complications of physical findings amongst patients with FSS; and (3) treatment types and outcomes. All papers reporting diagnosis of FSS, SHS, DA1, and DA3 are included in searching PubMed and Google Scholar from December 2014 to July 2015 and again before final analyses. Patients with FSS are divided into four phenotype-defined sub-types; all patients are grouped by published diagnosis and medical speciality. Significance of physical findings and historical data is evaluated by chi-square. Associations of physical findings and history with diagnosis and treatment outcome are evaluated by Pearson correlation and linear regression analysis. Two-tailed alpha level of 0.05 is used throughout. The need for detailed patient-level data extraction may limit the types of articles included and questions able to be answered. For treatment and psychosocial health outcomes, we anticipate enhanced difficulties, which may limit significance, power, and results' usability. We hope to outline knowledge gaps and prioritise areas for clinical investigation. CRD42015024740 Universal Trial Number: U1111-1172-4670.

The distal arthrogryposis (DA) syndromes are a group of disorders characterized by congenital contractures of limbs. According to phenotypical characteristics, DA syndromes have been clinically classified into 10 types. Currently, at least nine disease causing genes have been identified for different types of DA. Here, we report a 3-generation Chinese pedigree with three DA affected members. We performed whole exome sequencing on two affected and one unaffected individuals of this family and successfully identified a novel missense mutation in TNNI2 as the pathogenic mutation. The TNNI2 gene encodes a subunit of the troponin complex, a contractile machinery of the muscle. The mutation p.F178C that could change the H-bond formation of a neighboring residue occurs at a highly conserved position, suggesting that this variation probably affects the TNNI2 protein function. Our study also demonstrates the power of whole exome sequencing in causal mutation identification for phenotypically variable and genetically heterogeneous disorders.