Malignant Hyperthermia and Absence of Ryanodine Receptors in a Child Presenting for Ptosis Repair

Introduction: Malignant hyperthermia (MH) is a hypermetabolic condition caused by a genetic cell membranes channel disruption leading to increased calcium release from the sarcoplasmic reticulum after exposure to triggering agents. Central Core Disease (CCD) is a rare inherited neuromuscular disorder with a wide spectrum of phenotypic presentations. Clinically, there is muscle weakness of variable degree and histopathologically there is evidence of core formation in the muscle fibers. Additional features may occur, including skeletal abnormalities such as foot deformities, scoliosis, or hip displacement. Association of CCD with a mutation of the ryanodine receptor RYR1 and MH is high. If not properly treated, MH could be fatal. Purpose: This study aims towards increasing the awareness of pediatricians, surgeons and anesthesiologists about possible occurrence of MH in patients presenting with only mild “clinical” signs of congenital myopathies such as CCD. Careful diagnostic investigations should be performed prior to surgical interventions and extreme caution during anesthesia. Material and Methods: We report the case of a 3 years old girl, with a history of ptosis, scoliosis, and good muscle tone, who developed unexpected MH during the surgical repair of her ptosis. The critically ill child was transferred to Pediatric Intensive Care Unit (PICU) for management of her MH. The management was done following the guidelines of the European Malignant Hyperthermia Group published in the British Journal of Anesthesia 2010. The patient responded well to treatment. She had a muscle biopsy done after recovery. Discussion: Early management and dantrolene administration are the most important factors to minimize MH morbidity and mortality. MH susceptibility is known in patients carrying mutations in the RYR1 receptors. In our case, RYR1 staining was negative on the muscle biopsy specimen suggesting abnormal or absent RYR1 function, with the presence of occasional cores. These findings, in addition to the ophthalmological and orthopedic history were diagnostic of CCD. In Vitro Contracture Testing (IVCT) was not done because it was not available. Genetic testing was refused by the parents due to financial reasons. Conclusion: In patients presenting with symptoms suggestive of muscle weakness, such as ptosis and scoliosis, and variable muscle tone; congenital myopathies should be considered. CCD and RYR1 receptors deficiency or mutation, if present, may lead to a possible risk of fatal MH, which can be prevented.