A diagnosis of MD has genetic implication for family members. It is therefore important that the diagnosis be made as soon as possible, so that genetic advice can be offered. Affected boys always have very high levels of SK and a normal or slightly increased level rules out the diagnosis. A suspicion of any type of MD is investigated by diagnostic tests. Electromyography consists of observing the electrical activity generated in muscle when it contracts, through a needle inserted in the muscle.
Muscle biopsy is usually the confirmatory test.
A small piece of muscle is removed for examination under a microscope and sometimes also for chemical examination. It is sometimes possible to get a satisfactory specimen through a needle, using local anaesthetic, which makes it a very minor procedure. Sometimes a general anaesthetic and a surgical incision are necessary. It is now possible to detect the abnormal gene for a number of the MD's and other inherited muscle diseases. This can be done by examining the DNA extracted from a blood sample.