Rare Disease Report

Free Genetic Testing for Periodic Paralysis Available

SEPTEMBER 25, 2017
James Radke
Strongbridge Biopharma announced the launch of a free genetic test to diagnose hyperkalemic or hypokalemic periodic paralysis.

Many cases of periodic paralysis are due to a genetic mutation in 1 of 3 genes; SCN4A, CACNA1S, and KCNJ2. The panel tests for all 3 of these genes, and Strongbridge recently gained approval of their orphan drug Keveyis (dichlorphenamide) to treat the condition.

Primary paralysis is often difficult to diagnose for 2 reasons: first, it is a rare disease affecting approximately 4000-5000 people in the United States. Additionally, the symptoms of periodic paralysis (muscle weakness or paralysis) are often short-lived, and by the time a person who is partially paralyzed gets seen by a doctor familiar with the condition, the symptoms may no longer be present.

The disease is usually due to genetic mutations that make ion channels in muscles more vulnerable to changes in potassium levels. The 2 most common forms of periodic paralysis are hyperkalemic periodic paralysis and hypokalemic period paralysis.

Symptoms vary dramatically between patients, but common symptoms that may be observed in hypokalemic periodic paralysis include:
  • Weakness or paralysis in muscles in the hips, shoulders, arms, legs, and/or eyes
  • Symptoms appear after sleep or rest
  • Activities that appear to trigger an attack include:
    • Exercising
    • Eating a high-carbohydrate or high-salt meal
    • Consuming alcohol
  • Paralysis usually lasts 3 to 24 hours
  • Potassium blood levels are low
  • Severe cases usually present in childhood while mild cases may present later in adulthood

Symptoms observed in hyperkalemic periodic paralysis can vary greatly but may include:
  • Weakness after strenuous exercise or during fasting
  •  “Heavy” or “stiff” muscles
  • High potassium blood levels
In a news release,  Matthew Pauls, president and chief executive officer of Strongbridge Biopharma said: “Primary Periodic Paralysis patients have historically been underserved, and we are proud to offer them robust support from Strongbridge’s patient- and physician-focused programs. Additionally, given the early market interest in Keveyis (dichlorphenamide), the first and only FDA-approved treatment for hyperkalemic, hypokalemic, and related variants of primary periodic paralysis, and to better serve the needs of patients and the physicians who treat them, we are expanding our 12-person field force team to 21 employees by early November.”

 “There is a growing awareness of periodic paralysis and access to tests such as this may help shorten the diagnostic journey for patients,” said Steve Cannon M.D., PhD, neurologist and professor of Physiology at UCLA. “Access to more reliable genetic testing will empower medical professionals with the right information to facilitate improved clinical management of the disease.”

Since periodic paralysis is a genetic disease, Strongbridge will also offer free genetic testing to first-degree relatives of patients diagnosed with periodic paralysis.

For more information, visit UncoveringPeriodicParalysis.com.

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