Amyoplasia involving only the upper limbs or only involving the lower limbs with review of the relevant differential diagnoses

Fetal arthrogryposis-what do we tell the prospective parents?

Arthrogryposis, also termed arthrogryposis multiplex congenita, is a descriptive term for conditions with multiple congenital contractures (MCC). The etiology is extremely heterogeneous. More than 400 specific disorders have been identified so far, which may lead to or are associated with MCC and/or fetal hypo- and akinesia as a clinical sign. With improved sensitivity of prenatal ultrasound and expanding prenatal diagnostic options, clinicians are tasked with providing early detection in order to counsel the prospective parents regarding further prenatal diagnostic as well as management options. We summarize the most important knowledge to raise awareness for early detection in pregnancy. We review essential points for counseling when MCC is detected in order to provide answers to common questions, which, however, cannot replace interdisciplinary expert opinion in the individual case.

Case Report: Congenital Arthrogryposis and Unilateral Absences of Distal Arm in Congenital Zika Syndrome

Zika virus was recognized as a teratogen in 2015, when prenatal Zika infection was associated with neonatal microcephaly. The transmission, virulence, tropism, and consequences of Zika virus infection during pregnancy are currently studied. Decreased neural progenitor cells, arrest in neuronal migration and/or disruption of the maturation process of the fetus central nervous system have been associated. Congenital Zika Syndrome produces a fetal brain disruption sequence resulting in structural brain abnormalities, microcephaly, intracranial calcifications, fetal akinesia and arthrogryposis. Vascular abnormalities like unique umbilical artery and decreased cerebral vascular flow have been described in some patients. This article reports a Zika positive patient with sequence of fetal brain disruption, arthrogryposis and absence of distal third of the right forearm. This report expands the clinical observations of congenital Zika syndrome that may be related to disruptive vascular events.

The mystery of monozygotic twinning I: What can Amyoplasia tell us about monozygotic twinning and the possible role of twin-twin transfusion?

Amyoplasia is a very specific, nongenetic clinically recognizable form of arthrogryposis, representing about one-third of individuals with arthrogryposis surviving the newborn period. There is a markedly increased number of individuals with Amyoplasia who are one of monozygotic (MZ) twins, with the other twin being normal. Thus, it would appear that Amyoplasia is definitely associated with and may be caused by an MZ twinning event. The twin-twin transfusion seen in MZ twins could play an etiologic role in producing Amyoplasia. In this article, Amyoplasia twinning is compared to twinning in other forms of arthrogryposis. The accompanying paper examines various types of MZ twinning (Hall, 2021). Amyoplasia is primarily associated with spontaneous MZ twinning.

Mutations in MYLPF Cause a Novel Segmental Amyoplasia that Manifests as Distal Arthrogryposis

We identified ten persons in six consanguineous families with distal arthrogryposis (DA) who had congenital contractures, scoliosis, and short stature. Exome sequencing revealed that each affected person was homozygous for one of two different rare variants (c.470G>T [p.Cys157Phe] or c.469T>C [p.Cys157Arg]) affecting the same residue of myosin light chain, phosphorylatable, fast skeletal muscle (MYLPF). In a seventh family, a c.487G>A (p.Gly163Ser) variant in MYLPF arose de novo in a father, who transmitted it to his son. In an eighth family comprised of seven individuals with dominantly inherited DA, a c.98C>T (p.Ala33Val) variant segregated in all four persons tested. Variants in MYLPF underlie both dominant and recessively inherited DA. Mylpf protein models suggest that the residues associated with dominant DA interact with myosin whereas the residues altered in families with recessive DA only indirectly impair this interaction. Pathological and histological exam of a foot amputated from an affected child revealed complete absence of skeletal muscle (i.e., segmental amyoplasia). To investigate the mechanism for this finding, we generated an animal model for partial MYLPF impairment by knocking out zebrafish mylpfa. The mylpfa mutant had reduced trunk contractile force and complete pectoral fin paralysis, demonstrating that mylpf impairment most severely affects limb movement. mylpfa mutant muscle weakness was most pronounced in an appendicular muscle and was explained by reduced myosin activity and fiber degeneration. Collectively, our findings demonstrate that partial loss of MYLPF function can lead to congenital contractures, likely as a result of degeneration of skeletal muscle in the distal limb.

Elbow Release and Tricepsplasty in Arthrogrypotic Patients: A Long-Term Follow-Up Study

PURPOSE

Obtaining elbow flexion to improve hand-to-mouth reach capability is an essential component of achieving functional independence in pediatric patients with arthrogryposis. This study analyzed the long-term outcomes of elbow release and tricepsplasty in a series of children with arthrogryposis at a tertiary institution.

METHODS

Medical records of patients with arthrogryposis who underwent elbow release and tricepsplasty from 1993 to 2015, with at least 2 years of follow-up, were reviewed. Collected measures included preoperative elbow passive range of motion (ROM), postoperative elbow passive and active ROM, shoulder passive and active ROM, and Pediatric Outcomes Data Collection Instrument (PODCI) scores. Our analysis compared pre- and postoperative follow-up of elbow passive ROM and reviewed PODCI scores with age-adjusted normative values.

RESULTS

Seventeen patients (4 female and 13 male) with 24 affected upper extremities (10 left elbow and 14 right elbow) were included in final analysis. Age at final follow-up averaged 11 years (range, 4-20 years), mean age at surgery was 2.7 years (range, 9.6 months-9.3 years) with mean follow-up by extremity at 8.3 years (range, 2-18 years). Differences in pre- and post-operative passive elbow ROM were significant for extension, flexion, and total arc of motion. Most parent and self-reported PODCI scores were less than the age-adjusted normal population, except in the domains of Comfort and Pain and Happiness.

CONCLUSION

Long-term follow-up of elbow release and tricepsplasty in patients with arthrogryposis indicates both increased and sustained elbow flexion and arc of motion. Although PODCI scores were lower compared with the age-adjusted norm, pediatric patients with arthrogryposis were just as happy and had no more discomfort than their unaffected age-adjusted norms.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Fetal arthrogryposis: Challenges and perspectives for prenatal detection and management

Antenatal identification of fetuses with multiple congenital contractures or arthrogryposis multiplex congenita (AMC) may be challenging. The first clinical sign is often reduced fetal movement and/or contractures, as seen on prenatal ultrasounds. This can be apparent at any point, from early to late pregnancy, may range from mild to severe involvement, with or without associated other structural anomalies. Possible etiologies and their prognosis need to be interpreted with respect to developmental timing. The etiology of AMC is highly heterogeneous and making the specific diagnosis will guide prognosis, counseling and prenatal and perinatal management. Current ultrasound practice identifies only approximately 25% of individuals with arthrogryposis prenatally before 24 weeks of pregnancy in a general obstetrics care population. There are currently no studies and guidelines that address the question of when and how to assess for fetal contractures and movements during pregnancy. The failure to identify fetuses with arthrogryposis before 24 weeks of pregnancy means that physicians and families are denied reproductive options and interventions that may improve outcome. We review current practice and recommend adjusting the current prenatal imaging and genetic diagnostic strategies to achieve early prenatal detection and etiologic diagnosis. We suggest exploring options for in utero therapy to increase fetal movement for ongoing pregnancies.

Genetics and Classifications

Arthrogryposis multiplex congenital (AMC) is a descriptive term for a group of conditions that all share the characteristic of congenital contractures. There are an estimated 400 discrete diagnoses that can lead to a child being born with arthrogryposis. The 2 biggest categories of conditions are amyoplasia and distal arthrogryposis, which combined make up ∼50% to 65% of all diagnoses within the AMC subset. Amyoplasia, the most common AMC condition, seems to be a nongenetic syndrome, leading to very characteristic upper and lower limb contractures. The distal arthrogryposes, in contrast, have an underlying genetic abnormality, which in many cases seems to target the fast twitch muscles of the developing fetus. Classifying AMC is a difficult task, given the broad range of conditions represented. Four different classification schemes are presented.