- Malignant hyperthermia (HP:0002047): Malignant hyperthermia is characterized by a rapid increase in temperature to 39-42 degrees C. Malignant hyperthermia may occur in response to either inhalational anesthetics such as halothane, to muscle relaxants such as succinylcholine, or to exercise. Evidence: PCS. Frequency: 1/1. (PMID:23911890)
- Myokymia (HP:0002411): Myokymia consists of involuntary, fine, continuous, undulating contractions that spread across the affected striated muscle. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Abnormal reflex (HP:0031826): Any anomaly of a reflex, i.e., of an automatic response mediated by the nervous system (a reflex does not need the intervention of conscious thought to occur). Evidence: PCS. Frequency: 0/5. (PMID:8841193)
- Myotonia (HP:0002486): An involuntary and painless delay in the relaxation of skeletal muscle following contraction or electrical stimulation. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Flexion contracture (HP:0001371): A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Somatic sensory dysfunction (HP:0003474): An abnormality of the primary sensation that is mediated by peripheral nerves (pain, temperature, touch, vibration, joint position). The word hypoesthesia (or hypesthesia) refers to a reduction in cutaneous sensation to a specific type of testing. Evidence: PCS. Frequency: 0/5. (PMID:8841193)
- EMG: myotonic discharges (HP:0100284): High frequency discharges in electromyography (EMG) that vary in amplitude and frequency, waxing and waning continuously with firing frequencies ranging from 150/second down to 20/second and producing a sound that has been referred to as a dive bomber sound. Evidence: PCS. Frequency: 0/5. (PMID:8841193)
- Fasciculations (HP:0002380): Fasciculations are observed as small, local, involuntary muscle contractions (twitching) visible under the skin. Fasciculations result from increased irritability of an axon (which in turn is often a manifestation of disease of a motor neuron). This leads to sporadic discharges of all the muscle fibers controlled by the axon in isolation from other motor units. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: PCS. Frequency: 1/1. (PMID:23911890)
- Percussion myotonia (HP:0010548): A localized myotonic contraction in a muscle in reaction to percussion (tapping with the examiner's finger, a rubber percussion hammer, or a similar object). Evidence: PCS. Frequency: 0/10. (PMID:10914677;PMID:8841193)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. Frequency: 5/5. (PMID:10914677)
- Difficulty running (HP:0009046): Reduced ability to run. Evidence: PCS. Frequency: 1/5. (PMID:10914677)
- Autosomal recessive inheritance (HP:0000007): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: PCS. (PMID:8841193)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Skeletal muscle hypertrophy (HP:0003712): Abnormal increase in muscle size and mass not due to training. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Exercise-induced muscle stiffness (HP:0008967): A type of muscle stiffness that occurs following physical exertion. Evidence: PCS. Frequency: 10/10. (PMID:10914677;PMID:8841193)
- Exercise-induced muscle cramps (HP:0003710): Sudden and involuntary contractions of one or more muscles brought on by physical exertion. Evidence: PCS. Frequency: 1/1. (PMID:23911890)
- Myalgia (HP:0003326): Pain in muscle. Evidence: PCS. Frequency: 0/5. (PMID:10914677)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/1. (PMID:23911890)
These phenotypes are associated with the disease Brody myopathy (OMIM:601003).