Familial Periodic Paralysis

The familial periodic paralysis is a rare autosomal disease with considerable differences in severity. It is gekennzeichent by episodes flaccid paralysis with loss of deep tendon reflexes and the absence of electrical stimulation of the muscle. There are four forms: hypokaliämisch, hyperkalemic, thyreotoxisch and Andersen-Tawil syndrome. The diagnosis is based on history and provocation of an episode confirmed (administration of a glucose-insulin mixture to hypokalemia or potassium chloride to induce a hyperkalemia). Treatment depends on the current form.

Any form of familial periodic paralysis affects another gene and electrolyte channel. At 70% the hypokalaemic form occurs due to a mutation in the alpha subunit of the voltage-sensitive muscle calcium channel gene on chromosome 1q (HypoPP type I). In some families, the mutation is in the ?-subunit of the sodium channel gene on chromosome 17 (HypoPP type II). Although it is the most common form of familial periodic paralysis, the hypokalaemic form is still quite rare, with a prevalence of 1 / 100,000. The hyperkalemic form due to mutations in a gene encoding the ?-subunit of the skeletal muscle sodium channel (SCN4A). The mutations affected and electrolyte channels in thyrotoxic form are unknown, but this form usually includes hypokalemia and is associated with symptoms of hyperthyroidism. The incidence of thyrotoxic form is highest among Asian men. The Andersen-Tawil syndrome is caused by an autosomal dominant defect in the inward potassium channel. Affected patients can have a high, low or normal levels of potassium in the blood.

The familial periodic paralysis is a rare autosomal disease with considerable differences in severity. It is gekennzeichent by episodes flaccid paralysis with loss of deep tendon reflexes and the absence of electrical stimulation of the muscle. There are four forms: hypokaliämisch, hyperkalemic, thyreotoxisch and Andersen-Tawil syndrome. The diagnosis is based on history and provocation of an episode confirmed (administration of a glucose-insulin mixture to hypokalemia or potassium chloride to induce a hyperkalemia). Treatment depends on the current form. Any form of familial periodic paralysis affects another gene and electrolyte channel. At 70% the hypokalaemic form occurs due to a mutation in the alpha subunit of the voltage-sensitive muscle calcium channel gene on chromosome 1q (HypoPP type I). In some families, the mutation is in the ?-subunit of the sodium channel gene on chromosome 17 (HypoPP type II). Although it is the most common form of familial periodic paralysis, the hypokalaemic form is still quite rare, with a prevalence of 1 / 100,000. The hyperkalemic form due to mutations in a gene encoding the ?-subunit of the skeletal muscle sodium channel (SCN4A). The mutations affected and electrolyte channels in thyrotoxic form are unknown, but this form usually includes hypokalemia and is associated with symptoms of hyperthyroidism. The incidence of thyrotoxic form is highest among Asian men. The Andersen-Tawil syndrome is caused by an autosomal dominant defect in the inward potassium channel. Affected patients can have a high, low or normal levels of potassium in the blood. Symptoms and complaints hypokalemic events usually begin before the age of 16 years. Patients often wake up in the morning with a muscle weakness after they have done hard physical work the previous day. The weakness can be easy and limited to specific muscle groups or it can detect all four extremities. Incidents are triggered by carbohydrate meals, emotional or physical stress, alcohol consumption and exposure to cold. Oropharyngeal muscles and respiratory muscles remain mostly spared. Consciousness is not changed. Serum and urine potassium are reduced. The weakness lasts up to 24 h.Hyperkalämische incidents often start at a younger age. They are usually shorter, more frequent and less severe. The attacks can be triggered by rest after physical exertion, vigorous exercise after meals or fasting. A myotonia (prolonged recovery after a muscle contraction) is frequently observed. A myotonic eyelid may be the only symptom sein.Thyreotoxische attacks can last from hours to days and are usually caused by exercise, stress, exercise or carbohydrate intake, similar triggered as the hypokalemic form. The symptoms are those of hyperthyroidism (eg. As anxiety, emotional lability, weakness, tremor, palpitations, heat intolerance, increased sweating, weight loss). Clinical features of hyperthyroidism often precede periodic paralysis over months and years. However, the clinical features of hyperthyroidism but are also found at the same time as this paralysis (up to 60% of patients) or after the development of a periodic paralysis (at up to 17% of patients) .Andersen-Tawil syndrome transactions begin in usually before the age of 20 with all or some components of the following triad periodic paralysis Prolonged QT interval and ventricular arrhythmias dysmorphic physical characteristics to the dysmorphic physical characteristics include short stature, high-arched palate, low-set ears, broad nose, micrognathia, hypertelorism, clinodactyly the fingers short finger and syndactyly of the toes. The attacks can be triggered by rest after physical exertion, lasting several days and occur monthly. Diagnosis Clinical evaluation serum potassium determination while symptoms sometimes provocative testing The best clue is a history of typical attacks. During the incidents the determination of serum potassium is important. The incidents can administration of glucose and insulin (hypokalaemic form) and potassium chloride (hyperkalemic form) are provoked sometimes. But only experienced doctors should perform these provocations, since it can come during the incidents to respiratory paralysis and cardiac conduction disturbances. Treatment depends on the type and severity of seizures hypokalaemic The hypokalaemic paralysis can take the administration of KCl 2-10 g in an oral solution or unsweetened with i.v. treat potassium. Avoiding a high-carb diet, a low-sodium diet, avoiding heavy physical activity or alcohol after periods of rest and acetazolamide 250-2000 mg po once daily can hypokalaemic seizures vorbeugen.Hyperkalämische incidents with mild paralysis can be stopped during insertion by slight movement and by oral administration of 2 g / kg carbohydrates A fully trained incident requires the supply of thiazide, acetazolamide or inhaled ?-mimetics. Serious incidents require calcium gluconate or insulin and i.v. Glucose. The frequent intake of carbohydrate-rich, low-potassium meal and a waiver of fasting, physical stress, and exposure to cold can beitragen.Thyreotoxische to avoid hyperkalämischen attack Acute incidents with potassium chloride treated (familial periodic paralysis: hypokalaemic). Serum potassium level is to be accurately controlled. Incidents by maintaining a euthyroid state and by the gift of a ?-blocker prevented (hyperthyroidism: Treatment) (eg, propranolol.) Andersen-Tawil syndrome Besides lifestyle changes including strictly controlled exercises or activity, seizures may by the gift of a carbonic anhydrase inhibitor (e.g., acetazolamide example) can be prevented. The main complication of Andersen-Tawil syndrome is a sudden death from cardiac arrhythmias and a pacemaker or implantable cardioverter defibrillator may be necessary to control cardiac symptoms. Summary There are 4 types of familial periodic paralysis, caused by mutations of rare membrane electrolyte channels. The serum potassium is usually, but not always, unusually high or low. Patients have intermittent episodes of weakness, usually triggered by motion and sometimes meals (especially if they contain carbohydrates) or alcohol. The diagnosis is made by typical symptoms and the determination of serum potassium during the symptoms. Incidents are treated by correcting the potassium levels, and lifestyle choices through a change.

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