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Familial hyperkalemic periodic paralysis(HYPP)

MedGen UID:
68665
Concept ID:
C0238357
Disease or Syndrome
Synonyms: Adynamia episodica hereditaria with or without myotonia; Gamstorp disease; Gamstorp episodic adynamy; Hyperkalemic periodic paralysis
SNOMED CT: Familial hyperkalemic periodic paralysis (304737009); Hyperkalemic periodic paralysis (304737009); Adynamia episodica hereditaria (304737009); Gamstorp disease (304737009); Periodic paralysis II (304737009)
 
Gene (location): SCN4A (17q23.3)
 
HPO: HP:0007215
Monarch Initiative: MONDO:0008224
OMIM®: 170500

Disease characteristics

Excerpted from the GeneReview: Hyperkalemic Periodic Paralysis
Hyperkalemic periodic paralysis (hyperPP) is characterized by attacks of flaccid limb weakness (which may also include weakness of the muscles of the eyes, throat, breathing muscles, and trunk), hyperkalemia (serum potassium concentration >5 mmol/L) or an increase of serum potassium concentration of at least 1.5 mmol/L during an attack of weakness and/or provoking/worsening of an attack by oral potassium intake, normal serum potassium between attacks, and onset before age 20 years. In approximately half of affected individuals, attacks of flaccid muscle weakness begin in the first decade of life, with 25% reporting their first attack at age ten years or older. Initially infrequent, the attacks then increase in frequency and severity over time until approximately age 50 years, after which the frequency of attacks declines considerably. The major attack trigger is eating potassium-rich foods; other triggers include: cold environment; rest after exercise, stress, or fatigue; alcohol; hunger; and changes in activity level. A spontaneous attack commonly starts in the morning before breakfast, lasts for 15 minutes to one hour, and then passes. Individuals with hyperPP frequently have myotonia (muscle stiffness), especially around the time of an episode of weakness. Paramyotonia (muscle stiffness aggravated by cold and exercise) is present in about 45% of affected individuals. More than 80% of individuals with hyperPP older than age 40 years report permanent muscle weakness and about one third develop a chronic progressive myopathy. [from GeneReviews]
Authors:
Frank Weber   view full author information

Additional description

From MedlinePlus Genetics
Hyperkalemic periodic paralysis is a condition that causes episodes of extreme muscle weakness or paralysis, usually beginning in infancy or early childhood. Most often, these episodes involve a temporary inability to move muscles in the arms and legs. Episodes tend to increase in frequency until mid-adulthood, after which they occur less frequently in many people with the condition. Factors that can trigger attacks include rest after exercise, potassium-rich foods such as bananas and potatoes, stress, fatigue, alcohol, pregnancy, exposure to hot or cold temperatures, certain medications, and periods without food (fasting). Muscle strength usually returns to normal between attacks, although many affected people continue to experience mild stiffness (myotonia), particularly in muscles of the face and hands.

Most people with hyperkalemic periodic paralysis have increased levels of potassium in their blood (hyperkalemia) during attacks. Hyperkalemia results when the weak or paralyzed muscles release potassium ions into the bloodstream. In other cases, attacks are associated with normal blood potassium levels (normokalemia). Ingesting potassium can trigger attacks in affected individuals, even if blood potassium levels do not go up.  https://medlineplus.gov/genetics/condition/hyperkalemic-periodic-paralysis

Clinical features

From HPO
Familial hyperkalemic periodic paralysis
MedGen UID:
68665
Concept ID:
C0238357
Disease or Syndrome
Hyperkalemic periodic paralysis (hyperPP) is characterized by attacks of flaccid limb weakness (which may also include weakness of the muscles of the eyes, throat, breathing muscles, and trunk), hyperkalemia (serum potassium concentration >5 mmol/L) or an increase of serum potassium concentration of at least 1.5 mmol/L during an attack of weakness and/or provoking/worsening of an attack by oral potassium intake, normal serum potassium between attacks, and onset before age 20 years. In approximately half of affected individuals, attacks of flaccid muscle weakness begin in the first decade of life, with 25% reporting their first attack at age ten years or older. Initially infrequent, the attacks then increase in frequency and severity over time until approximately age 50 years, after which the frequency of attacks declines considerably. The major attack trigger is eating potassium-rich foods; other triggers include: cold environment; rest after exercise, stress, or fatigue; alcohol; hunger; and changes in activity level. A spontaneous attack commonly starts in the morning before breakfast, lasts for 15 minutes to one hour, and then passes. Individuals with hyperPP frequently have myotonia (muscle stiffness), especially around the time of an episode of weakness. Paramyotonia (muscle stiffness aggravated by cold and exercise) is present in about 45% of affected individuals. More than 80% of individuals with hyperPP older than age 40 years report permanent muscle weakness and about one third develop a chronic progressive myopathy.
Myotonia
MedGen UID:
675119
Concept ID:
C0700153
Finding
An involuntary and painless delay in the relaxation of skeletal muscle following contraction or electrical stimulation.
Episodic flaccid weakness
MedGen UID:
871107
Concept ID:
C4025572
Finding
Recurrent episodes of muscle flaccidity, a type of paralysis in which a muscle becomes soft and yields to passive stretching.
Hyperkalemia
MedGen UID:
5691
Concept ID:
C0020461
Finding
An abnormally increased potassium concentration in the blood.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVFamilial hyperkalemic periodic paralysis
Follow this link to review classifications for Familial hyperkalemic periodic paralysis in Orphanet.

Conditions with this feature

Familial hyperkalemic periodic paralysis
MedGen UID:
68665
Concept ID:
C0238357
Disease or Syndrome
Hyperkalemic periodic paralysis (hyperPP) is characterized by attacks of flaccid limb weakness (which may also include weakness of the muscles of the eyes, throat, breathing muscles, and trunk), hyperkalemia (serum potassium concentration >5 mmol/L) or an increase of serum potassium concentration of at least 1.5 mmol/L during an attack of weakness and/or provoking/worsening of an attack by oral potassium intake, normal serum potassium between attacks, and onset before age 20 years. In approximately half of affected individuals, attacks of flaccid muscle weakness begin in the first decade of life, with 25% reporting their first attack at age ten years or older. Initially infrequent, the attacks then increase in frequency and severity over time until approximately age 50 years, after which the frequency of attacks declines considerably. The major attack trigger is eating potassium-rich foods; other triggers include: cold environment; rest after exercise, stress, or fatigue; alcohol; hunger; and changes in activity level. A spontaneous attack commonly starts in the morning before breakfast, lasts for 15 minutes to one hour, and then passes. Individuals with hyperPP frequently have myotonia (muscle stiffness), especially around the time of an episode of weakness. Paramyotonia (muscle stiffness aggravated by cold and exercise) is present in about 45% of affected individuals. More than 80% of individuals with hyperPP older than age 40 years report permanent muscle weakness and about one third develop a chronic progressive myopathy.
Pseudohypoaldosteronism type 2A
MedGen UID:
327088
Concept ID:
C1840389
Disease or Syndrome
Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia despite normal glomerular filtration rate (GFR) and frequently by hypertension. Other associated findings in both children and adults include hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. Aldosterone levels are variable, but are relatively low given the degree of hyperkalemia (elevated serum potassium is a potent stimulus for aldosterone secretion). Hypercalciuria is well described.

Professional guidelines

PubMed

Jurkat-Rott K, Lehmann-Horn F
Neurotherapeutics 2007 Apr;4(2):216-24. doi: 10.1016/j.nurt.2007.02.001. PMID: 17395131

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