- Episodic flaccid weakness (HP:0003752): Recurrent episodes of muscle flaccidity, a type of paralysis in which a muscle becomes soft and yields to passive stretching. Evidence: PCS. Frequency: 1/1. (PMID:18835861)
- Myotonia (HP:0002486): An involuntary and painless delay in the relaxation of skeletal muscle following contraction or electrical stimulation. Evidence: PCS. Frequency: 0/1. (PMID:18835861)
- Myopathy (HP:0003198): A disorder of muscle unrelated to impairment of innervation or neuromuscular junction. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:170400)
- Hypotonia (HP:0001252): Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist. Evidence: PCS. Frequency: 1/1. (PMID:18835861)
- Typified by incomplete penetrance (HP:0003829): Description of conditions in which not all individuals with a given genotype exhibit the disease. Penetrance is the proportion that develop disease given a lifespan of 80 years. Evidence: TAS. (OMIM:170400)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 1/1. (PMID:18835861)
- Hypokalemia (HP:0002900): The concentration of potassium(1+) in the blood circulation is below the lower limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:18835861)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. (OMIM:170400)
- Periodic paralysis (HP:0003768): Episodes of muscle weakness. Evidence: PCS. Frequency: 1/1. (PMID:18835861)
- Autosomal dominant inheritance (HP:0000006): 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 heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:8004673)
These phenotypes are associated with the disease hypokalemic periodic paralysis, type 1 (OMIM:170400).