Basic Reading

Nondystrophic Myotonias and Periodic Paralyses

This chapter from McGraw Hill's Myology, third edition; editors Andrew Engel and Clara Franzini-Armstrong,  give a comprehensive look at the nondystrophic myotonias and periodic paralyses, written by one of the world's top teams in the field.

Chapter from Myology, third edition: Nondystrophic Myotonias and Periodic Paralyses by Frank Lehmann-Horn, Reinhardt Rudel and Karin Jurkat-Rott.

Our thanks to Professor Dr. Lehmann-Horn, Dr. Jurkat-Rott and Dr. Rudel for your kind permission to include this valuable information on our website!

Thyrotoxic Hypokalemic Periodic Paralysis

Clinical Synopsis

Thyrotoxic periodic paralysis (THKPP) is an uncommon disorder characterized by simultaneous thyrotoxicosis, hypokalemia, and paralysis that occurs primarily in males of Asian descent, including patients of Japanese, Chinese, Vietnamese, Korean and Filipino ancestry.

Comparison of Five Forms of Periodic Paralysis

Introduction:

The major features found in all the periodic paralyses are:

1. Attacks almost always begin before the age of 25, though occasionally later in life. ATS patients can develop first symptoms at any age.

2. Serum potassium fluctuates shortly before an attack, but serum potassium level will normalize before the attacks resolves and will be within the normal range between attacks. This is not a disorder of the blood but one in which there is an inappropriate shift of fluid, K+ and NA+ during attacks. 

Physician's Summary: Andersen-Tawil Syndrome

Andersen-Tawil Syndrome (ATS) is a genetic disorder which causes a distinctive pattern of features;

1) Episodes of muscle weakness and/or flaccid paralysis (i.e periodic paralysis)

2) Certain kinds of heart rhythm disturbances and

3) Differences in facial and body structure.

Summary of Hyperkalemic Periodic Paralysis

Clinical Signs

Hyperkalemic Periodic Paralysis is a genetically determined disorder which causes attacks of weakness and flaccid paralysis. Attacks last from 10 min to 1 hour, very rarely up to 1-2 days. Some patients experience only a few attacks over their lifetime, others have attacks every day. Diagnosis is suggested by attacks of weakness during which the patient's serum potassium is above 5.0 mmol/l or rises at least .5 of a mmol/l above their normal level when not in an attack.

The Abortive Attack - Weakness Between Attacks

Are Weakness and Fatigue Between Paralytic Attacks Symptoms of Periodic Paralysis?

Potassium Supplementation and B-12 Deficiency

Patients who take potassium chloride long-term, i.e., are at risk for developing vitamin B-12 deficiency. Potassium supplements such as K-Dur, Micro-K, Slow-K, K-Lyte, etc. interfere with the absorption of vitamin B-12 and can eventually lead to the depletion of body stores of this crucial vitamin. 1, 2, 3

Paramyotonia Congenita & Paramyotonia Syndromes

Paramyotonia Congenita (PMC) is one of the periodic paralyses caused by mutations in the sodium channel. PMC causes muscle stiffness (myotonia) which is made worse by chilling or activity. Myotonia usually eases when the patients moves about, or "warms up" through physical activity. In PMC myotonia develops during activity, which is paradoxical or self-contradictory. This is where Paramyotonia Congenita gets its name, from the paradoxical nature of the myotonia.

Thyrotoxic Hypokalemic Periodic Paralysis FAQ

What is Thyrotoxic Hypokalemic Periodic Paralysis?

Thyrotoxic Hyperkalemic Periodic Paralysis (TPP) is an uncommon disorder with three characteristics which occur at the same time:  

  1. too much thyroid hormone

  2. low levels of potassium in the blood (hypokalemia)

  3. muscle weakness or paralysis 

Andersen-Tawil Syndrome FAQ

What is Andersen-Tawil Syndrome?

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