Hypokalemic periodic paralysis type 1

Hypokalemic Periodic Paralysis Type 1

Hypokalemic periodic paralysis type 1 (HypoPP1) is a rare genetic disorder characterized by episodes of muscle weakness associated with low levels of potassium in the blood. It is a subtype of periodic paralysis, a group of disorders that affect the ability of muscles to contract properly.

Etiology

HypoPP1 is caused by mutations in the CACNA1S gene, which encodes the alpha-1 subunit of a voltage-dependent calcium channel. This channel is crucial for the normal function of skeletal muscle cells. Mutations in this gene disrupt the normal flow of calcium ions, leading to episodes of muscle weakness.

Pathophysiology

The pathophysiology of HypoPP1 involves the dysfunction of ion channels in muscle cells. The mutation in the CACNA1S gene affects the calcium channels, which in turn affects the sodium and potassium ion balance across the muscle cell membrane. During an attack, there is an abnormal influx of sodium ions and efflux of potassium ions, leading to depolarization of the muscle cell membrane and muscle weakness.

Clinical Presentation

Patients with HypoPP1 typically present with episodes of muscle weakness or paralysis that can last from a few hours to several days. These episodes are often triggered by factors such as:

• High carbohydrate meals
• Rest after exercise
• Stress
• Cold temperatures

The weakness usually affects the proximal muscles more than the distal muscles and can lead to complete paralysis in severe cases.

Diagnosis

Diagnosis of HypoPP1 is based on clinical presentation, family history, and genetic testing. Laboratory tests during an attack may show low serum potassium levels. Electromyography (EMG) and muscle biopsy can also aid in diagnosis.

Management

Management of HypoPP1 involves both acute treatment of attacks and long-term prevention. Acute attacks are treated with oral or intravenous potassium supplements. Long-term management includes:

• Potassium-sparing diuretics
• Carbonic anhydrase inhibitors such as acetazolamide
• Avoidance of known triggers

Prognosis

The prognosis for individuals with HypoPP1 varies. With proper management, many individuals can lead normal lives, although some may experience progressive muscle weakness over time.

Also see

• Periodic paralysis
• Hyperkalemic periodic paralysis
• Andersen-Tawil syndrome
• Ion channelopathy