Most people with this condition begin to develop muscle weakness (myopathy) in mid-adulthood. However, symptoms can appear anytime between infancy and late adulthood.
People with myofibrillar myopathies can experience weakness and wasting in the muscles of their hands, arms ankles and calves. Affected people may experience difficulties with small tasks using their hands owing to the weakness in their hands, or frequent falls owing to weakness in their feet.
With the progression of the condition, weakness in the muscles closer to the body can also develop, but occasionally this can be present from the onset. Other signs and symptoms of myofibrillar myopathies can include muscle pain (myalgia), joint stiffness (contractures) and abnormal side-to-side curvature of the spine (scoliosis).
Muscles responsible for speech and swallowing can also be affected leading to swallowing difficulties (choking episodes) and changes in the tone of voice.
Heart problems can be mild or severe and may manifest as arrhythmia, conduction defects or congestive heart failure.
Muscles used for breathing may also get weaker, causing breathing difficulties and leading to respiratory insufficiency.
Some people with myofibrillar myopathies may also experience loss of sensation (paresthesia, tingling and numbness) and weakness related to damage of the peripheral nerves (peripheral neuropathy).
In some cases people with myofibrillar myopathies can also develop blurred vision as a result of cataracts.