Abnormal protrusion of the scapula away from the surface of the back.

The shoulder, or pectoral, girdle is composed of the clavicles and the scapulae. Shoulder-girdle weakness refers to lack of strength of the muscles attaching to these bones, that is, lack of strength of the muscles around the shoulders.

Weakness of the muscles of the pelvic girdle (also known as the hip girdle), that is, lack of strength of the muscles around the pelvis.

Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles.

The term gait disturbance can refer to any disruption of the ability to walk.

A lack of strength of the proximal muscles.

A contracture of the Achilles tendon.

A decrease in the strength of the diaphragm.

Weakness of the quadriceps muscle (that is, of the muscle fasciculus of quadriceps femoris).

Fiber splitting or branching is a common finding in human and rat skeletal muscle pathology. Fiber splitting refers to longitudinal halving of the complete fiber, while branching originates from a regenerating end of a necrotic fiber as invaginations of the sarcolemma. In fiber branching, one end of the fiber remains intact as a single entity, while the other end has several branches.

Muscle hypertrophy affecting the calf muscles.

Weakness of the muscles involved in neck flexion (sternocleidomastoid, longus capitus, longus colli, and scalenus anterior).

An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy.

Presence of abnormal vacuoles (membrane-bound organelles) in the sarcolemma. On histological staining with hematoxylin and eosin, rimmed vacuoles are popcorn-like clear vacuoles with a densely blue rim. The vacuoles are often associated with cytoplasmic and occasionally intranuclear eosinophilic inclusions.

In rare cases, the muscles used for speaking, swallowing, or breathing are affected in people with myofibrillar myopathy. When the muscles used for breathing are involved, affected individuals may experience extreme tiredness (fatigue), breathing difficulties, and, in severe cases, respiratory failure. \n\nSome people with myofibrillar myopathy develop cardiomyopathy, which is a weakening of the heart muscle. In some cases, cardiomyopathy is the first sign of the disorder.\n\nOther signs and symptoms of myofibrillar myopathy can include muscle pain (myalgia) or weakness and loss of sensation in the limbs (peripheral neuropathy). Affected individuals may also have skeletal problems, which can include joint stiffness (contractures) and abnormal side-to-side curvature of the spine (scoliosis). Some people with myofibrillar myopathy develop clouding in the lenses of the eyes (cataracts).\n\nThe signs and symptoms of myofibrillar myopathy vary widely among affected individuals. People with this disorder typically begin to develop myopathy in mid-adulthood. However, the features of this condition can appear anytime between infancy and late adulthood. Myopathy most often begins in the hands, forearms, feet, and lower legs (distal muscles), but some people first experience weakness in the muscles near the center of the body (proximal muscles). The weakness can spread to other muscles. \n\nMyofibrillar myopathy refers to a group of disorders that are characterized by muscle weakness (myopathy) that worsens over time. Myofibrillar myopathy primarily affects the skeletal muscles, which are the muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected.

An abnormal reduction on the vital capacity, which is defined as the total lung capacity (volume of air in the lungs at maximal inflation) less the residual volume (i.e., volume of air in the lungs following maximal exhalation) of the lung.

A severe form of respiratory insufficiency characterized by inadequate gas exchange such that the levels of oxygen or carbon dioxide cannot be maintained within normal limits.

An abnormal reduction in alveolar ventilation occurring during sleep. This is characterized by a rise in arterial carbon dioxide.

An elevation of the level of the enzyme creatine kinase (also known as creatine phosphokinase (CK; EC 2.7.3.2) in the blood. CK levels can be elevated in a number of clinical disorders such as myocardial infarction, rhabdomyolysis, and muscular dystrophy.