MH is an inherited disorder carried on the RYR-1 gene. It can be caused by several different mutations of that same gene.
People are often diagnosed after having a reaction during surgery. A person may also choose to have a muscle biopsy if they are suspected to have had a reaction or a blood relative is suspected to have had a reaction.
More recently, DNA testing has become available but the muscle biopsy CHCT test is the gold standard at this time.