Myofibrillar myopathies are a group of conditions called myopathies that affect muscle function and cause weakness. They primarily affect skeletal muscles.
A weakening of the heart muscle (cardiomyopathy) is also common and may manifest as arrhythmia, conduction defects or congestive heart failure.
Myofibrillar myopathies are always progressive and muscle weakness worsens over time, however the rate of progression may vary from person to person and also depending on the specific condition.
The course of the condition can be variable from mild weakness to severe, leading to loss of ambulation in some people.
Life-expectancy is generally within the normal range, however this depends on identification and treatment of heart problems and breathing difficulties.