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Arthrogryposis Multiplex Congenita

Arthrogryposis Multiplex Congenita Deep Research Fallback

⚠️ Fallback MONDO:0015168

Arthrogryposis Multiplex Congenita Deep Research Fallback

Provider Attempts

  • 2026-05-13: Automated deep-research providers (falcon, asta, cyberian-codex, perplexity, openai) were unavailable in the curation environment for this disorder. No provider-generated research artifact was produced.

No provider-generated research artifact was available to integrate. Curation therefore proceeded from a manual literature synthesis built around the canonical AMC clinical and molecular references listed below, without hand-editing any references_cache/*.md files.

Evidence Scope Used For Curation

  • PMID:24459070 (Hall JG, Amyoplasia revisited) — the canonical 560-patient Amyoplasia case series. Provides the foundational clinical description of Amyoplasia, supports its sporadic recurrence pattern, documents the characteristic symmetric limb positioning (extended elbows, equinovarus feet), and reports fatty-fibrous replacement of muscle. Used for the Amyoplasia subtype, the Sporadic inheritance entry, the Congenital contracture / Limb joint contracture / Talipes equinovarus phenotypes, and the Clinical pattern recognition diagnostic entry.
  • PMID:24459095 (Hall JG, Amyoplasia involving only the upper limbs or only the lower limbs) — complementary differential-diagnosis paper for Amyoplasia; included in references: as background for the Amyoplasia clinical group.
  • PMID:27587986 (Hall JG, Kiefer J, Arthrogryposis as a Syndrome: Gene Ontology Analysis) — synthesis paper explicitly framing decreased in utero fetal movement (fetal akinesia) as the shared mechanistic pathway across all genetic AMC subtypes. Anchors the "Decreased fetal movement" pathophysiology node and the Decreased fetal movement phenotype.
  • PMID:25256237 (Beck AE et al., Genotype-phenotype relationships in Freeman-Sheldon syndrome) — 46-family DA2A series. Establishes MYH3 as causative for Freeman-Sheldon syndrome (DA2A) and quantifies the three recurrent missense variants (p.T178I, p.R672C, p.R672H) that account for the majority of DA2A cases. Used for the Heterozygous MYH3 variants genetic entry.
  • PMID:38856159 (Morali et al., Bi-allelic variants in MYH3 cause recessively-inherited arthrogryposis) — extends MYH3 from a purely dominant gene (Freeman-Sheldon, Sheldon-Hall, multiple pterygium) to a recessive cause of distal arthrogryposis. Provides the standard "two-or-more body areas" clinical definition of arthrogryposis used in the Congenital contracture and Arthrogryposis multiplex congenita phenotype entries, the Autosomal recessive inheritance entry, and the Exome / genome sequencing diagnostic entry.
  • PMID:30285720 (Li B et al., Novel mutations in TPM2 and PIEZO2 are responsible for distal arthrogryposis (DA) 2B and mild DA in two Chinese families) — provides a heterozygous TPM2 missense variant segregating with DA2B (Sheldon-Hall syndrome) in a multigenerational family. Used for the Heterozygous TPM2 variants genetic entry. The same paper performs linkage analysis with markers at TPM2, TNNI2/TNNT3, and TNNC2, which is used as PARTIAL evidence for the Heterozygous TNNI2 variants entry (which carries an Associated association rather than Causative, pending addition of a dedicated TNNI2 causative-variant citation in a future revision).
  • PMID:32799913 (Guo P et al., Drosophila myosin DA1/DA2B models) — the mechanistic paper supporting prolonged actomyosin interactions as the proximal sarcomeric defect in DA1 and DA2B. Tagged with evidence_source: MODEL_ORGANISM for the sarcomeric contractile-protein dysfunction pathophysiology node and for the autosomal dominant inheritance characterization (their introduction frames the DAs as autosomal dominant skeletal muscle diseases).
  • PMID:31479584 (Shriners multiauthored review, Treatment and outcomes of arthrogryposis in the lower extremity) — anchors early intensive physiotherapy and bracing as the central, evidence-supported management for AMC, and emphasizes a multidisciplinary care model.
  • PMID:22875688 (Lampasi et al., Management of knee deformities in children with arthrogryposis) — enumerates the orthopedic surgical procedures (soft-tissue release, femoral shortening-extension osteotomy, Ilizarov gradual correction, femoral anterior epiphysiodesis) used to address residual knee contractures in AMC.

Literature Synthesis

Arthrogryposis Multiplex Congenita (AMC) is an umbrella clinical phenotype — defined by congenital joint contractures involving two or more different body areas — rather than a single disease (PMID:38856159). The condition is etiologically heterogeneous and includes more than 400 recognized genetic disorders together with the sporadic, classical form Amyoplasia (PMID:24459070). Across all forms, the most consistent unifying mechanistic feature is decreased in utero fetal movement: "All types of arthrogryposis have decreased in utero fetal movement." (PMID:27587986). Persistent fetal hypokinesia prevents normal stretching of muscle and periarticular connective tissue, producing fixed congenital contractures, fatty-fibrous replacement of muscle, characteristic limb positioning (extended elbows, equinovarus feet), and the broader fetal akinesia deformation sequence findings (PMID:24459070, PMID:27587986).

Clinically, AMC is divided into four major groups. Amyoplasia, the most common single form, is sporadic, "completely sporadic" in Hall's 560-patient series (PMID:24459070), and is characterized by symmetric severe limb contractures, fatty-fibrous muscle replacement, characteristic limb positioning, and typically preserved cognition; it remains "a clinical diagnosis at this time" (PMID:24459070). The distal arthrogryposis (DA) syndromes are typically autosomal dominant disorders preferentially affecting the hands and feet, including DA1, DA2A (Freeman-Sheldon, the most severe), and DA2B (Sheldon-Hall) (PMID:25256237, PMID:32799913). The multiple pterygium syndromes combine congenital contractures with pterygia across flexural joints and include the autosomal recessive Escobar variant and the lethal multiple pterygium syndrome. The lethal congenital contracture syndromes (LCCS) are prenatal- or perinatal-lethal disorders in the fetal akinesia deformation sequence spectrum.

Molecularly, the dominant DA syndromes are caused predominantly by heterozygous variants in genes encoding sarcomeric contractile proteins. MYH3 (embryonic myosin heavy chain) is the most common single gene cause: "Heterozygous variants in MYH3 have been identified to cause the dominantly-inherited distal arthrogryposis conditions, Freeman-Sheldon syndrome, Sheldon-Hall syndrome, and multiple pterygium syndrome." (PMID:38856159). In Beck et al.'s 46-family DA2A series, "MYH3 mutations were found in 43/46 (93%) kindreds, with three mutations (p.T178I, p.R672C, and p.R672H) explaining 39/43 (91%) of cases." (PMID:25256237). MYH3 also underlies a recessive form of distal arthrogryposis (PMID:38856159). Heterozygous TPM2 (beta-tropomyosin) variants cause DA2B and related distal arthrogryposis phenotypes (PMID:30285720). TNNI2 (fast skeletal troponin I) is grouped with TPM2 in the thin-filament regulatory cluster of distal arthrogryposis candidate loci (PMID:30285720); the present entry classifies TNNI2 with association: Associated and a PARTIAL evidence tag, because the Li et al. paper used TNNI2 as a linkage candidate locus rather than itself demonstrating a pathogenic TNNI2 variant. Functional Drosophila modeling demonstrates that DA1 and DA2B sarcomeric variants produce prolonged actomyosin interactions, which plausibly reduces effective fetal movement and produces the congenital contracture phenotype (PMID:32799913).

Management of AMC is lifelong and multidisciplinary, centered on early intensive physiotherapy and orthotic bracing: "The importance of very early and aggressive management of these deformities in the form of intensive physiotherapy (with its various modalities) and bracing is emphasized." (PMID:31479584). Selective orthopedic surgical procedures — soft-tissue release, femoral shortening-extension osteotomy, gradual correction with Ilizarov frames, and femoral anterior epiphysiodesis — address residual contractures not corrected by conservative measures (PMID:22875688). Care delivery emphasizes "the central role of a multidisciplinary approach involving all stakeholders, especially the families" (PMID:31479584). Genetic counseling is integral, given the sporadic nature of Amyoplasia and the autosomal dominant or recessive recurrence risks in the Mendelian forms.

Curation Conclusions

The accepted unifying model of AMC is decreased in utero fetal movement (fetal akinesia) producing fixed congenital joint contractures across two or more body areas. The mechanism is gene-agnostic at the level of the final common pathway, but converges from many proximal causes — most prominently sarcomeric contractile-protein dysfunction in the distal arthrogryposes (MYH3, TPM2, TNNI2). The dismech graph therefore models three pathophysiology nodes (decreased fetal movement, sarcomeric contractile-protein dysfunction, congenital joint contracture formation) linked by downstream edges that capture the conserved final-common pathway. Subtype assignment is clinically anchored (Amyoplasia, distal arthrogryposis, multiple pterygium syndromes, LCCS) and is informed by contracture distribution, associated craniofacial and prenatal features, and family history, with exome / genome sequencing used to identify causative Mendelian variants. Detailed gene-specific pathophysiology and management belong in dedicated subtype entries; the present entry itemizes only the most informative thin- and thick-filament DA genes (MYH3, TPM2, TNNI2).