Anaesthetic management of a paediatric patient with congenital fibre type disproportion myopathy

A novel RYR1 variant in an infant with a unique fetal presentation of central core disease

Ryanodine receptor type 1-related disorder (RYR1-RD) is the most common subgroup of congenital myopathies with a wide phenotypic spectrum ranging from mild hypotonia to lethal fetal akinesia. Genetic testing for myopathies is imperative as the diagnosis informs counseling regarding prognosis and recurrence risk, treatment options, monitoring, and clinical management. However, diagnostic challenges exist as current options are limited to clinical suspicion prompting testing including: single gene sequencing or familial variant testing, multi-gene panels, exome, genome sequencing, and invasive testing including muscle biopsy. The timing of diagnosis is of great importance due to the association of RYR1-RD with malignant hyperthermia (MH). MH is a hypermetabolic crisis that occurs secondary to excessive calcium release in muscles, leading to systemic effects that can progress to shock and death if unrecognized. Given the association of MH with pathogenic variants in RYR1, a diagnosis of RYR1-RD necessitates an awareness of medical team to avoid potentially triggering agents. We describe a case of a unique fetal presentation with bilateral diaphragmatic eventrations who had respiratory failure, dysmorphic facial features, and profound global hypotonia in the neonatal period. The diagnosis was made at several months of age, had direct implications on her clinical care related to anticipated need to long-term ventilator support, and ultimately death secondary an arrhythmia as a result of suspected MH. Our report reinforces the importance of having high suspicion for a genetic syndrome and pursuing early, rapid exome or genome sequencing as first line testing in critically ill neonatal intensive care unit patients and further evaluating the pathogenicity of a variant of uncertain significance in the setting of a myopathic phenotype.

Peripartum Management of Congenital Fiber Type Disproportion Myopathy With Severe Restrictive Lung Disease

Congenital myopathies raise unique challenges for anesthesiologists during labor and delivery. Apart from having a risk for malignant hyperthermia, this patient population can present with severe restrictive lung disease in the third trimester. Scoliosis and weak pelvic muscles could make regional anesthesia difficult. The common complications in pregnancy include premature labor, preterm delivery, spontaneous abortion, a prolonged first stage of labor, and uterine atony. We report a case of 28-year-old primigravida of 37 weeks gestation diagnosed with congenital fiber type disproportion successfully managed by a team of high-risk obstetricians, anesthesiologists, and pulmonologists. The patient was closely monitored with serial arterial blood gas to determine carbon dioxide retention in a high-risk labor floor with a backup operating room for cesarean delivery. We reserved a malignant hyperthermia cart and a postpartum hemorrhage cart for emergencies. Our patient was able to deliver vaginally with the help of ultrasound-guided regional anesthesia despite having severe restrictive lung disease and scoliosis. We emphasize a multi-disciplinary team approach for a successful outcome for this patient population.

The R168G heterozygous mutation of tropomyosin 3 (TPM3) was identified in three family members and has manifestations ranging from asymptotic to serve scoliosis and respiratory complications

According to existing reports, mutations in the slow tropomyosin gene (TPM3) may lead to congenital fiber-type disproportion (CFTD), nemaline myopathy (NM) and cap myopathy (CD). They are all congenital myopathies and are associated with clinical, pathological and genetic heterogeneity. A ten-year-old girl with scoliosis was unable to wean from mechanical ventilation after total intravenous anesthesia. The girl has scoliosis, respiratory insufficiency, motion delay and muscle weakness; her younger brother has a similar physiology but does not have scoliosis or respiratory insufficiency, and her parents are healthy. We conducted genetic testing and found a c.502C > G (p.R168G) heterozygous mutation in the family. This mutation originated from the father and was autosomal dominant. Muscle biopsy results indicated that no special structures were present, and the type I fiber ratio was not notably high compared to previous reports. Although the family members have the same mutations, their clinical manifestations are quite different.