Pediatric Periodic Hypokalemic Paralysis

Brief introduction of children with periodic hypokalemia Periodic paralysis is a group of diseases characterized by recurrent, self-limiting episodes of skeletal muscle flaccid paralysis. According to the change of blood potassium at the time of onset, it can be divided into three types: hypokalemia type, hyperkalemia type and normal blood potassium type. The hypokalemic peripheral paralysis is characterized by flaccid paralysis of skeletal muscle and a decrease in serum potassium at the onset. The disease is autosomal dominant, with incomplete penetrance, and scattered cases. The disease gene is located in the long arm region of chromosome 1 (Iq3.1-3.2). basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: heart failure

The cause of periodic hypokalemia paralysis in children

(1) Causes of the disease

In Europe and the United States, most of them are autosomal dominant inheritance. In China, sporadic cases are more common. Satisfaction, alcoholism, cold, strenuous exercise, excessive mental stress, injection of glucose and insulin, and use of adrenal cortex hormones can induce the disease. The cause is not yet clear and is currently thought to be related to fluctuations in potassium concentration inside and outside the cell.

(two) pathogenesis

Because the potassium excretion did not increase before the onset, it is speculated that the decrease of serum potassium in the attack period may be caused by the shift of blood potassium to muscle cells. Electrophysiological studies confirmed that the sarcolemma was hyperpolarized when the extracellular potassium concentration decreased. Muscle stimulation of nerves is reduced, which may lead to muscle paralysis. Pathological findings include muscle biopsy during the onset of the episode, formation of sarcoplasmic vacuoles, and vacuoles containing glycogen, suggesting that the disease may be a defect in carbohydrate metabolism in muscle fibers. As a result, when the muscle function is restored, the vacuole disappears. Generally, the muscle biopsy of the episode should show normal. When the lesion becomes irreversible, it is permanent myopathy (PM), so the PM patient even Degenerative changes such as vacuoles can also be seen in the interictal muscle biopsy.

Periodic hypokalemia paralysis in children

1. Avoid incentives, try to avoid seizures, such as cold, excessive exercise.

2. Take potassium chloride, taking potassium chloride every night before going to bed can prevent seizures.

Children with periodic hypokalemia palsy complications Complications heart failure

It can cause respiratory disorders, heart enlargement or heart failure, and permanent cardiomyopathy can occur.

Children with periodic hypokalemia paralysis symptoms common symptoms hypokalemia fatigue fatigue paralysis metabolic hypokalemia heart failure

The disease is reported to be the first to occur in 8 to 21 years of age in 88% of cases. Beijing Children's Hospital has seen that the incidence of a child is 4 years old. It is consistent with foreign reports. Boys are more common. Children with intermittent episodes have no symptoms and no muscles. Atrophy, intermittent period can vary from several days to several years, the time of paralysis is uncertain, more common when sleeping and resting, eating carbohydrates, being frightened, nervous, trauma, infection and menstruation are all predisposing factors. Sometimes local flaccid paralysis can be induced by immersion of cold water in the limbs, which can be gradually relieved by immersing the limbs in warm water.

Pre-existing symptoms often include prodromal symptoms such as muscle stiffness, fatigue, abnormal limbs, drowsiness, headache, etc., or excitement, nervousness, anxiety, polydipsia, etc. on the day before the onset. It can be predicted that paralysis often starts from the proximal muscles of the extremities. The most common first symptom is the weakness of both lower limbs, and it can also extend to the distal end of the limb. The range of paralysis is different. From several groups of muscles to the whole body, the light is only weak. It is still possible to walk; in addition to facial muscles, eye muscles, muscles related to pronunciation and speech, muscles, sphincters, skeletal muscles of the whole body can be affected, the degree of paralysis can be complete or incomplete, such as paralysis Widely, sometimes it can cause respiratory disorders, heart enlargement or heart failure. During the episode, the sacral reflex declines or disappears, the feeling is normal, and the perception and consciousness are unchanged. The duration of each episode is as short as 1~3h, and more often 6~24h. Individual cases can last up to about 1 week.

In 1891, Oppenheim first reported that permanent myopathy can occur in patients with periodic paralysis. It can be found in children, adolescents and adults. One case was diagnosed in Beijing Children's Hospital. The clinical manifestations were chronic progressive proximal muscle weakness and muscle atrophy. The pelvic muscles, the quadriceps muscles are weak, the shoulder muscles and the neck muscles are relatively light, the disease is mostly neglected, the severe ones can affect the distal muscles of the limbs, and even lose muscle function, can only be in a wheelchair or Bedridden, it is reported that permanent myopathy has nothing to do with the frequency and severity of paralysis; but it is closely related to age. The older the age, the higher the incidence and the more severe the symptoms, thus supporting the essence of the disease as muscle. Organize the view of damage.

The disease can be recurrent, and severe cases often die from heart failure or respiratory disorders. Generally speaking, there is a tendency to reduce the attack after middle age.

Examination of periodic hypokalemia paralysis in children

Blood test

When paralysis occurs, the serum potassium level of the child can be lowered and the blood phosphorus is also lowered.

2. Urine check

Urine potassium does not increase.

3. Glucose induction test

Under the monitoring of ECG in individual suspected cases, glucose-induced test can help diagnose. The blood potassium and electrocardiogram of the children before the test are normal. Then the children take oral glucose 50g (2g/kg), and the subcutaneous insulin is 10U (0.4U/kg). After that, the muscle strength, blood potassium and electrocardiogram changes were observed every 1h. If the limb weakness occurred in the observation process, the serum potassium decreased to 3.5mmol/L or less, indicating that the test result is positive, and the method is simple and easy. Safe and reliable, but the negative results of the test can not completely exclude the disease, because some children may not respond to glucose and insulin.

4. ECG examination

ECG shows that the PR and QT intervals are prolonged, U waves appear, ST segments fall and T waves are inverted.

5. Electromyography

EMG during the episode can show impaired myogenicity, reduced motor potential time, and reduced amplitude.

Diagnosis and differential diagnosis of children with periodic hypokalemia

diagnosis

Diagnose based on:

1. History: Provides paroxysmal flaccid paralysis without sensory disturbance.

2. Laboratory examination: serum potassium is less than 3.5mmol/L at the time of onset.

3. Treatment response: Potassium salt treatment is effective.

4. Exclude other diseases: exclude secondary hypokalemia caused by other diseases.

Differential diagnosis

For the first author, it should be differentiated from acute polyradiculitis, polymyositis, and secondary hypokalemia caused by other causes.

The disease is distinguished from the Guillain-Barre syndrome. The latter is more common in the onset of lower limbs and affects both upper limbs and symmetrical flaccid paralysis. When the progressive aggravation is 5-7 days, the condition is as high as peak. Sensory disorder, cerebrospinal fluid has protein cell separation, and electromyography shows neurogenic damage.

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