Muscle cramps are common and mild facial weakness has been seen in some cases, specifically involving the eyes. Weakness around the hips can lead to hip dislocations or tightening of the joints (contractures), particularly the knees and hips. Curvature of the spine (scoliosis) may also occur. Generally the heart and respiratory function are not affected.
Malignant hyperthermia (MH) is an acute reaction triggered by certain general anaesthetics or muscle relaxants (which are used for general anaesthesia). Symptoms of MH include high fever, muscle rigidity, dark brown colouration of urine and acute kidney failure. MH is potentially fatal if not treated immediately with a drug called dantrolene. MH can be prevented by avoiding the triggering anaesthetic agents with alternative drugs. Local anaesthetics are quite safe. Both MH and central core disease are associated with abnormalities in the RYR1 gene, so it is important to inform the consultant surgeon or anaesthetist if surgery is being considered.