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Spasmophilia in children
Medical expert of the article
In pediatrics, a pathological tendency to involuntary muscle spasms and spontaneous convulsions - tetany (from the Greek tetanos - convulsion), caused by increased neuromuscular excitability in violation of calcium metabolism in the body, is often defined as spasmophilia in children. 
The development of rickets in children in developed countries, according to statistics, is 1-2 cases per 100 thousand babies in the first year of life; in Ukraine, pediatricians note signs of rickets in 3% of children under 6 months. 
According to some reports, in children suffering from rickets, spasmophilia develops in 3.5-4% of cases.
Causes of the spasmophilia in a child
The causes of convulsive syndrome or spasmophilia in children under two years of age may be due to:
- low calcium levels in a child at birth - hypocalcemia in newborns , which leads to an ionic imbalance in the blood;
- deficient vitamin D (calciferol) - rickets that usually occurs in infants aged 3 to 6 months;
- violation of the formation of 1,25-dihydroxyvitamin D (dihydroxycholecalciferol) in the kidneys, which is called hypocalcemic rickets or hereditary type III or IV phosphate diabetes; 
- dysfunction of the parathyroid glands - neonatal hypoparathyroidism, the result of which is a lack of circulating parathyroid hormone (parathyroid hormone or PTH) and, in turn, a decrease in calcium levels.
- cases of development of spasmophilia with hypokalemia in the absence of alkalosis are described. , 
Experts refer to the risk factors for spasmophilia in children:
- premature babies and underweight at the birth of full-term babies;
- toxicosis of mothers during pregnancy;
- vitamin D deficiency in pregnant women, as well as a history of preeclampsia, severe osteomalacia (softening of bone tissue with its low mineralization), gluten intolerance;
- asphyxia of newborns; 
- immaturity of the child's parathyroid glands at the time of birth;
- artificial feeding of the child;
- insufficient insolation (exposure to UV rays);
- malabsorption of vitamin D in the intestine;
- excess phosphate (hyperphosphatemia);
- low magnesium levels - autosomal dominant primary hypomagnesemia . , 
The pathogenesis of the state of increased excitability of the central and peripheral nervous system lies in disorders of perinatal metabolism and abnormal concentration of electrolytes in the blood serum, which leads to an increase in the frequency of the action potential of muscle cells or nerve fibers innervating muscles.
With rickets, either the metabolism of vitamin D (which is involved in mineral metabolism - the absorption of calcium in the intestine - and bone growth) is disturbed, or phosphorus-calcium metabolism, which ensures the formation of bone tissue and its mineralization.
Spasmophilia accompanied by generalized seizures and tremors in children under one year old may have a genetically determined mechanism:
- with vitamin D-dependent rickets type I associated with abnormalities in the gene that encodes the renal enzyme 25-hydroxy-D-1α-hydroxylase (CYP27B1), which is necessary to activate this vitamin with transformation (in the liver, kidneys and intestines) in 1, 25-dihydroxyvitamin D;
- with vitamin D-dependent rickets type II - hereditary 1,25-dihydroxyvitamin D-resistant rickets (also called hypophosphatemic rickets), which occurs due to a defective VDR gene (on chromosome 12q13), which encodes vitamin D receptors in body tissues and is involved in maintaining normal calcium levels; 
- with inherited hypoparathyroidism with impaired secretion of parathyroid hormone (PTH), which maintains serum calcium within certain limits;
- with primary hypomagnesemia, which not only leads to hypocalcemia, but also prevents the release of parathyroid hormone. In particular, magnesium deficiency in young children is possible due to mutations in the FXYD2 gene (which encodes the gamma subunit of the electrogenic transmembrane ATPase expressed in the distal renal tubules) or the HNF1B gene (which encodes the renal epithelial transcription factor). These genetic abnormalities (inherited or sporadic) are diagnosed as Gitelman's syndrome or Bartter's syndrome, and, in fact, refer to hereditary tubulopathies . 
What happens when the level of total and ionized calcium in the blood and interstitial fluid is insufficient ? The positive charge in the extracellular space decreases, and the membrane potential shifts towards depolarization - causing hyperexcitability of peripheral neurons and increasing the possibility of action potentials. And spontaneously arising action potentials provoke an involuntary contraction of the peripheral skeletal muscles.
Read also - Hypocalcemic crisis in children
Symptoms of the spasmophilia in a child
The first signs of spasmophilia - clonic and tonic seizures (convulsive syndrome) in children - with neonatal calcium deficiency can appear literally from the first days of birth or within two weeks after the birth of a child. 
Quite often, symptoms can be mild: in the form of focal muscle spasms and paresthesia. However, there are also painful tonic contractions of skeletal muscles - convulsions with spasmophilia in children or generalized cramps .
Also, the semiotics of spasmophilia in children includes laryngospasm - an involuntary contraction of the muscles of the larynx and vocal cords, leading to narrowing of the airways or their obstruction. With mild laryngospasm, the child's skin turns pale with the appearance of cold perspiration, stridor (wheezing) is observed. In this case, there may be an accelerated heartbeat and rapid intermittent breathing. The duration of such an attack does not exceed one and a half to two minutes, but during the day it can be repeated several times.
There are also spasms of the muscles of the hand (in the wrist) with extension of the interphalangeal joints, adduction and flexion of the metacarpophalangeal joints; spasms of the muscles of the feet near the ankles. These are the so-called carpopedal myospasms, which can be both short-term and longer-lasting - strong and quite painful. 
The most severe form is eclampsia in children with spasmophilia (from the Greek eklampsis - outbreak) or an attack of tonic-clonic seizures, which takes place in two stages. The first begins with twitching (fasciculations) of facial muscles and lasts 15-20 seconds; the second involves the spread of cramps to the limbs and muscles of the body; muscle spasms can last from 5 to 25 minutes. Laryngospasm, respiratory failure, general cyanosis, loss of consciousness, involuntary urination and defecation are also observed. 
In addition to the clinically pronounced form of spasmophilia, specialists note latent spasmophilia in children - latent tetany with almost normal calcium levels, which is often determined with rickets. When a child is frightened, after vomiting, and due to an increase in temperature with an infectious disease, this form can be transformed into a symptomatic one. How latent spasmophilia is detected, read further - in the Diagnostics section.
Complications and consequences
The main complications and consequences of spasmophilia in children are:
- general hypokinetic disorder;
- severe respiratory distress syndrome or respiratory arrest after laryngospasm or an attack of eclampsia;
- lengthening of the QT interval (detected by electrocardiography) with expansion of the ventricle - hypocalcemic dilated cardiomyopathy, leading to heart failure.
Prolonged attacks of tetany can lead to damage to the central nervous system, delay in the child's mental development in the future, and in severe cases, it can be fatal. 
Diagnostics of the spasmophilia in a child
Diagnosis begins with anamnesis and examination of the child. A positive sign of Khvostek allows him to suspect hypocalcemia before the results of laboratory tests are obtained: twitching of the muscles of the nose or lips when tapping the facial nerve between the earlobe and the corner of the mouth. 
And latent spasmophilia is usually determined by the so-called Trousseau sign, when cramps of the fingers of the hand, forced adduction of the thumb, flexion of the metacarpophalangeal joints and wrists appear when the brachial neurovascular bundle is occluded by compression.
In addition, the diagnostic criteria for spasmophilia in children are a decrease in the level of total calcium in the blood <1.75 mmol / L (in newborns <1.5 mmol / L) or iCa (ionized calcium) <0.65-0.75 mmol / l.
Blood tests for calcium, phosphate, plasma electrolytes, alkaline phosphatase and 1,25-dihydroxyvitamin D, PTH, urea nitrogen, and creatinine are required; urine analysis for the amount of excreted calcium and phosphate.
Instrumental diagnostics is carried out using electromigraphy of muscles (allowing to determine the level of neuromuscular conduction), as well as EEG - electroencephalography, which reveals the electrical activity of the brain. An EKG (electrocardiogram) and an MRI scan of the brain may be needed.
Proceeding from the fact that convulsions in children without excessive excitability of muscle fibers are not spasmophilia (tetany), differential diagnosis should exclude: birth trauma of the brain and ischemic encephalopathy; seizures provoked by increased intracranial pressure, dysgenesis / cerebral hypotrophy or cerebral vascular anomalies; epilepsy and epileptic encephalopathy (including mitochondrial and toxic); paroxysmal dyskinesias and dystonic hyperkinesias; dehydration of the body (caused by vomiting and / or diarrhea), as well as the manifestation of muscle spasms in congenital syndromes (Vesta, Menkes, Lennox-Gastaut, Schwartz-Jampel, etc.).
Also rickets, spasmophilia and hypervitaminosis D in children are differentiated. When intoxication with this vitamin, hypercalcemia, decreased appetite, frequent vomiting, sleep disorders, increased sweating, dehydration, and convulsions may also occur.
Treatment of the spasmophilia in a child
Clinical recommendations concern vitamin D deficiency: there is a Protocol for the treatment and prevention of rickets, approved by the Ministry of Health of Ukraine.
In case of a spasm of the muscles of the larynx, emergency care is required, read more - First aid for laryngospasm: an algorithm of actions
Treatment of spasmophilia in children is aimed at normalizing the level of calcium in the blood and relieving seizures, for which such basic drugs as calcium gluconate (10% solution) and magnesium sulfate (25% solution), which are administered parenterally, are used. 
The next steps in the treatment of this condition is the appointment of oral vitamin D3 preparations: Calciferol , Aquadetrim, Vigantol.
See also - Treatment of rickets
Prevention of spasmophilia is a timely diagnosis and appropriate treatment of rickets.
Prevention of rickets in children should also be carried out: monitoring the level of vitamin D during pregnancy and in case of its deficiency - ingestion from 28-32 weeks of gestation. Vitamin D3 preparations (5 mcg per day) are given to children. In addition, breastfeeding of the baby and adequate nutrition for women during lactation are important. For more information, see - How to prevent rickets?
When latent tetany is detected and eliminated, adequate correction of hypocalcemia, as well as timely assistance for laryngospasm and / or eclampsia in children with spasmophilia, the prognosis is favorable.
In severe cases of eclampsia, which most often affects children in the first year of life, respiratory and cardiac arrest is possible.