II. Epidemiology

  1. Prevalence: 1 in 100,000 (rare)
  2. Typical onset of symptoms before age 20 years
  3. More common in males

III. Causes

  1. Genetic
    1. Autosomal Dominant disorder of Hypokalemia
    2. Most often related to a Sodium channel disorder, with a shifting of Potassium into tissues
  2. Acquired
    1. Hyperthyroidism

IV. Risk Factors: Triggers

  1. Alcohol Abuse
  2. Corticosteroid use
  3. Insulin
  4. Renal disease
  5. Large Carbohydrate containing meals
  6. High salt intake
  7. Intense Exercise
  8. Glue sniffing
  9. Prolonged immobility
  10. Cold Weather
  11. Anesthetics

V. Symptoms

  1. Headaches
  2. Thirst
  3. Lethargy
  4. No associated pain

VI. Signs

  1. Slow progressive weakness (especially following triggers)
    1. Weakness lasts for hours to days
  2. Episodic muscular paralysis (lower extremities > upper extremities)
    1. Shoulder
    2. Pelvic girdle
    3. Other areas follow
  3. Muscle Strength normal between attacks
  4. Deep Tendon Reflexes
    1. Diminished or absent

VII. Associated Conditions

  1. Thyrotoxicosis
    1. Especially in young asian males, with onset after Exercise

VIII. Labs

  1. Consider extending evaluation to cover differential diagnosis as below
  2. Serum Electrolytes including Renal Function and Magnesium
    1. Serum Potassium with Hypokalemia during episode (normal between episodes)
    2. Hypomagnesemia may be associated with other causes of Hypokalemia
  3. Thyroid Stimulating Hormone (TSH)
    1. Evaluate for Thyrotoxicosis
  4. Genetic Testing
    1. Genetic outpatient testing if findings consistent with familial Hypokalemia

IX. Diagnostics

  1. Electrocardiogram
    1. See Hypokalemia for related EKG changes

X. Differential Diagnosis

XI. Management

  1. Replace Potassium IV in severe cases (oral Potassium in mild cases)
    1. See Potassium Replacement
    2. Exercise caution with replacement (risk of overshooting as Muscles release Potassium on recovery)
  2. Replace Magnesium if low
  3. Avoid high Carbohydrate intake
  4. Avoid Excessive Salt Intake

XII. Complications

XIII. Prevention

  1. Carbonic anhydrase inhibitors (e.g. Acetazolamide)
  2. Potassium sparing Diuretics (e.g. Spironolactone)

XIV. References

  1. Candy and Herbert in Herbert (2020) EM:Rap 20(11): 8-9
  2. Claudius and Behar in Herbert (2019) EM:Rap 19(11):12-3

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Ontology: Familial Periodic Paralysis (C0030443)

Definition (NCI) A group of genetic neurological disorders caused by mutations in genes involved in the sodium and calcium channels in nerve cells. It is characterized by episodes of muscle paralysis in which the affected muscles become flaccid and the deep tendon reflexes disappear. Between the episodes the affected muscles usually work normally.
Definition (MSH) A heterogenous group of inherited disorders characterized by recurring attacks of rapidly progressive flaccid paralysis or myotonia. These conditions have in common a mutation of the gene encoding the alpha subunit of the sodium channel in skeletal muscle. They are frequently associated with fluctuations in serum potassium levels. Periodic paralysis may also occur as a non-familial process secondary to THYROTOXICOSIS and other conditions. (From Adams et al., Principles of Neurology, 6th ed, p1481)
Definition (CSP) heterogenous group of inherited disorders characterized by recurring attacks of rapidly progressive flaccid paralysis or myotonia; these conditions have in common a mutation of the gene encoding the alpha subunit of the sodium channel in skeletal muscle; frequently associated with fluctuations in serum potassium levels; periodic paralysis may also occur as a non-familial process secondary to thyrotoxicosis and other conditions.
Concepts Disease or Syndrome (T047)
MSH D010245
ICD10 G72.3
SnomedCT 54696002, 193241004, 155099000, 267714003, 267607008
English Familial Periodic Paralyses, Paralyses, Familial Periodic, Paralysis, Familial Periodic, Periodic Paralyses, Familial, Periodic Paralysis, Familial, familial periodic paralysis, familial periodic paralysis syndrome (diagnosis), familial periodic paralysis syndrome, Paralysis periodic, Paralyses, Familial Periodic [Disease/Finding], periodic familial paralysis, periodic paralysis familial, periodic paralysis, familial paralysis periodic, paralysis periodic, Familial periodic paralysis, Cavarre disease, Familial myoplegia, Familial recurrent paralysis, Myoplegic dystrophy, Periodic myotonia, Familial periodic paralysis (disorder), paralysis; periodic, periodic; paralysis, Familial periodic paralysis, NOS, Periodic paralysis, Familial periodic paralysis (disorder) [Ambiguous], Familial Periodic Paralysis
Dutch paralyse periodiek, paralyse; periodiek, periodiek; paralyse, familiale periodieke paralyse, Familiale periodieke paralyse, Paralyse, familiale periodieke, Periodieke paralyse, familiale
French Paralysie périodique, Paralysie périodique familiale, Paralysies périodiques familiales
German Laehmung zeitweise, familiaere periodische Laehmung, Familiäre periodische Lähmungen, Lähmungen, familiäre periodische, Periodische Lähmungen, familiäre
Italian Paralisi periodica, Paralisi periodica familiare
Portuguese Paralisia periódica, Paralisia Periódica Normokalêmica, Paralisia periódica familiar, Paralisia Periódica Familiar, Paralisias Periódicas Familiares
Spanish Parálisis periódica, parálisis familiar periódica (trastorno), parálisis familiar periódica, parálisis periódica familiar, parálisis periódica familiar (trastorno), mioplejía familiar, parálisis recurrente familiar, parálisis periódica I, Parálisis Periódica Normokalémica, enfermedad de Cavarre, mioplejía periódica, miotonía periódica, parálisis familiar recurrente, parálisis periódica familiar (concepto no activo), Parálisis periódica familiar, Parálisis Familiar Periódica, Parálisis Periódicas Familiares
Japanese 周期性四肢麻痺, シュウキセイシシマヒ, カゾクセイシュウキセイマヒ, 周期性麻痺-家族性, 周期性四肢麻痺-正常カリウム血性, 正常カリウム血性周期性麻痺, 家族性周期性麻痺, 四肢麻痺-正常カリウム血性周期性, 周期性四肢麻痺-家族性, 周期性麻痺-正常カリウム血性, 正常カリウム血性周期性四肢麻痺, 麻痺-家族性周期性, 麻痺-正常カリウム血性周期性, 四肢麻痺-家族性周期性, 家族性周期性四肢麻痺
Swedish Paralyser, familjära periodiska
Czech paralýzy familiární periodické, Periodická obrna, Familiární periodická obrna
Finnish Familiaaliset periodiset paralyysit
Polish Porażenie okresowe rodzinne, Porażenie okresowe normokaliemiczne
Hungarian Periódikus paralysis, Familiaris periódikus paralysis
Norwegian Paralyse, familiær periodisk, Periodisk paralyse, familiær, Familiær periodisk paralyse

Ontology: Hypokalemic periodic paralysis (C0238358)

Definition (NCI) An autosomal dominant inherited or genetic disorder characterized by irregular episodes of muscle weakness or paralysis which are always accompanied by low levels of potassium in the blood.
Definition (MSH) An autosomal dominant familial disorder characterized by recurrent episodes of skeletal muscle weakness associated with falls in serum potassium levels. The condition usually presents in the first or second decade of life with attacks of trunk and leg paresis during sleep or shortly after awakening. Symptoms may persist for hours to days and generally are precipitated by exercise or a meal high in carbohydrates. (Adams et al., Principles of Neurology, 6th ed, p1483)
Concepts Disease or Syndrome (T047)
MSH D020514
ICD10 G72.3
SnomedCT 193241004, 240093008, 82732003, 54696002
English Famil.hypokalaem.period.paral., Hypokalaem periodic paralysis, FAMILIAL PERIODIC PARALYSIS <HYPOKALEMIC FORM>, periodic hypokalemic paralysis, FAMILIAL PERIODIC PARALYSIS HYPOKALEMIC FORM, Familial Hypokalemic Periodic Paralysis, Hypokalemic Periodic Paralysis, Familial, Hypokalemic Periodic Paralysis, Paralysis, Hypokalemic Periodic, Periodic Paralysis, Hypokalemic, Primary Hypokalemic Periodic Paralysis, Hypokalemic periodic paralysis (familial), Hypokalemic Periodic Paralysis [Disease/Finding], Periodic Paralysis- Hypokalemics, Periodic Paralysis Hypokalemic, Periodic Paralysis- Hypokalemic, hypokalaemic paralysis periodic, hypokalemic periodic paralysis, hypokalaemic periodic paralysis, hypokalemic paralysis periodic, periodic hypokalaemic paralysis, Westphall Disease, HYPOPP, HYPOKPP, HOKPP, Familial periodic paralysis (& [hypokalemic]), Familial periodic paralysis (& [hypokalaemic]) (disorder), Familial periodic paralysis (& [hypokalaemic]), Hypokalemic periodic paralysis (diagnosis), hypokalemic periodic paralysis syndrome, Hypokalemic periodic paralysis (disorder), Familial hypokalemic periodic paralysis, Periodic paralysis I, Familial hypokalaemic periodic paralysis, Hypokalaemic periodic paralysis, Familial hypokalemic periodic paralysis (disorder), Hypokalemic periodic paralysis, Hypokalemic familial periodic paralysis
Swedish Hypokalemisk periodisk paralys
Czech primární hypokalemická periodická paralýza, familiární hypokalemická periodická paralýza, hypokalemická periodická paralýza
Finnish Hypokaleeminen periodinen halvaus
Italian Paralisi periodica ipocaliemica familiare, Paralisi periodica ipocaliemica primaria, Paralisi periodica ipocaliemica
Polish Porażenie rodzinne hipokaliemiczne okresowe, Porażenie hipokaliemiczne okresowe
Japanese 家族性低カリウム性周期性麻痺, 四肢麻痺-低カリウム性周期性, 低カリウム性周期性麻痺, 低カリウム血性周期性四肢麻痺, 低カリウム性周期性四肢麻痺, 原発性低カリウム性周期性麻痺, 四肢麻痺-低カリウム血性周期性, 四肢麻痺-周期性-低カリウム血性, 麻痺-低カリウム性周期性, 麻痺-原発性低カリウム性周期性, 麻痺-周期性-低カリウム性-原発性, 麻痺-周期性-低カリウム性-家族性, 麻痺-周期性-原発性低カリウム性, 麻痺-周期性-家族性低カリウム性, 麻痺-家族性低カリウム性周期性
Norwegian Hypokalemisk periodisk paralyse
Spanish Parálisis Periódica Hipokalémica Primaria, Parálisis Periódica Hipokalémica Familiar, parálisis periódica hipocaliémica (trastorno), parálisis periódica hipocaliémica familiar (trastorno), parálisis periódica hipocaliémica familiar, parálisis periódica hipocaliémica, Parálisis Periódica Hipokalémica, Parálisis Periódica Hipopotasémica Familiar, Parálisis Periódica Hipopotasémica Primaria, Parálisis Periódica Hipopotasémica
Portuguese Paralisia Periódica Hipokalêmica Familiar, Paralisia Periódica Hipokalêmica Primária, Paralisia Periódica Hipokalêmica, Paralisia Periódica Hipopotassêmica Familiar, Paralisia Periódica Hipopotassêmica, Paralisia Periódica Hipopotassêmica Primária
French Paralysie périodique hypokaliémique, Maladie de Westphal, Paralysie périodique hypokaliémique de Westphal, Paralysie périodique primitive hypokaliémique de Westphal, Maladie de Westphall
German Familiäre hypokaliämische Lähmung, Hypokaliämisch-periodische Lähmung, Lähmung, hypokaliämisch-periodische, Primäre hypokaliämische periodische Lähmung
Dutch Familaire hypokaliëmische periodieke paralyse, Hypokaliëmische periodieke paralyse, Paralyse, hypokaliëmische periodieke, Periodieke paralyse, hypokaliëmische, Primaire hypokaliëmische periodieke paralyse