Welcome to the Rare Classroom, a new series from Patient Worthy. Rare Classroom is designed for the curious reader who wants to get informed on some of the rarest, most mysterious diseases and conditions. There are thousands of rare diseases out there, but only a very small number of them have viable treatments and regularly make the news. This series is an opportunity to learn the basics about some of the diseases that almost no one hears much about or that we otherwise haven’t been able to report on very often.

Eyes front and ears open. Class is now in session.

The disease that we will be learning about today is:

Alternating Hemiplegia of Childhood

What is Alternating Hemiplegia of Childhood?

• Alternating hemiplegia of childhood (AHC) is a very rare neurological disorder which is named for its episodes of hemiplegia (paralysis and/or weakness)
• The symptoms begin before 18 months of age
• A range of other symptoms can also appear and can vary considerably
• The disease was discovered relatively recently, and was first described in 1971
• AHC is extremely rare, with only one in 1,000,000 people having the disorder

How do you get It?

• In some cases, the cause of AHC is not known
• Usually, it is the result of a mutation of the ATP1A3 gene
• This genetic mutation isn’t passed down and instead appears to occur completely randomly
• This gene is found on chromosome 19
• A much smaller percentage of cases have been linked to a mutation of the ATP1A2 gene
• In the rare cases that the disorder is inherited, it is usually in an autosomal dominant pattern
• A strong family history of migraines has been reported in cases of AHC
  • Familial hemiplegic migraine is a closely related disorder

What are the Symptoms?

• The defining symptom of alternating hemiplegia of childhood are intermittent episodes of weakness and paralysis
  • Various triggers appear to cause hemiplegia attacks
    • Examples of triggers include certain foods, strong negative emotions, temperature changes, water exposure, and strenous physical activity
  • Severity can range from mild weakness to debilitating paralysis affecting one or both sides of the body
  • Symptoms may alternate from one side of the body or the other
  • Difficulty breathing, swallowing, and speaking may appear
  • Symptoms often appear at just a few months of age.
  • Other symptoms can include:
    • Tremors
    • Restlessness
    • Sweating
    • Screaming
    • Appearance of pain
• While symptoms may become less severe after the first decade of life, they don’t entirely go away
• Additional symptoms can also appear in AHC, such as:
  • Myoclonic, tonic-clonic, or tonic limb movements
  • Dystonic postures
  • Choreoathetosis
  • Cognitive deficits
  • Epilepsy

How is it Treated?

• Generally, AHC is highly debilitating and results in permanent damage. As a result, outcomes are generally rather poor
• However, the disorder does not appear to shorten lifespan or be fatal on its own
• Hemiplegic episodes appear to be occur as a result of various triggers. An important part of AHC management is recognizing triggers and avoiding them as much as possible
  • Unfortunately, some episodes occur without any apparent trigger
• Flunarizine, a calcium channel blocker, is the most common medication used for AHC.
  • This medicine is used to reduce the number of attacks and their severity, but it rarely halts episodes entirely
  • Opinions on its effectiveness are varied, as are results for patients. However, it is generally considered the most effective treatment
  • Unfortunately, it can be difficult to obtain, particularly in the US
• Other medicines used include barbiturates, valproic acid, carbamazapine, and benzodiazepines
• Sodium oxybate has been researched as a potential treatment without decisive results

Where Can I Learn More???

• Check out our cornerstone on this disease here.
• Learn more about this illness from Cure AHC.