Reduced strength and weakness of the muscles of the arms and legs.

Severe weight loss, wasting of muscle, loss of appetite, and general debility related to a chronic disease.

Difficulty in swallowing.

A sensation of unease in the stomach together with an urge to vomit.

Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions.

Decreased strength of the muscle layer of stomach, which leads to a decreased ability to empty the contents of the stomach despite the absence of obstruction.

Abnormal intestinal contractions, such as spasms and intestinal paralysis, related to the loss of the ability of the gut to coordinate muscular activity because of endogenous or exogenous causes.

A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve.

Absence of neurologic reflexes such as the knee-jerk reaction.

Inability to walk in a person who previous had the ability to walk.

Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.

A disorder of muscle unrelated to impairment of innervation or neuromuscular junction.

Reduced strength of one or more muscles innervated by the facial nerve (the seventh cranial nerve).

The presence of skeletal muscular atrophy (which is also known as amyotrophy).

An abnormality in which the nuclei of sarcomeres take on an abnormally central localization (or in which this feature is found in an increased proportion of muscle cells).

Reduced strength of the axial musculature (i.e., of the muscles of the head and neck, spine, and ribs).

An abnormal appearance of muscle fibers observed on muscle biopsy. Ragged red fibers can be visualized with Gomori trichrome staining as irregular and intensely red subsarcolemmal zones, whereas the normal myofibrils are green. The margins of affect fibers appear red and ragged. The ragged-red is due to the accumulation of abnormal mitochondria below the plasma membrane of the muscle fiber, leading to the appearance of a red rim and speckled sarcoplasm.

The presence of multiple deletions of mitochondrial DNA (mtDNA).

An abnormally reduced activity of the enzyme cytochrome C oxidase in muscle tissue.

The concentration of aspartate aminotransferase (AST) in the blood circulation is above the upper limit of normal.

An abnormally high concentration in the circulation of alanine aminotransferase (ALT).

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.

The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective).

Paralysis of one or more extraocular muscles that are responsible for eye movements.