Calcium Regulation

Living with 22q

What are the calcium problems see in children with the 22q11.2 Deletion Syndrome?
By Stuart A. Weinzimer, Paediatric Endrocrinologist at Children's Hospital of Philadelphia

Calcium Regulation
Children with the 22q11.2 deletion often have hypoparathyroidism, an underdevelopment of the glands that make parathyroid hormone (PTH). PTH is very important for the maintenance of normal calcium levels in the body. Without PTH, the calcium levels may drop to dangerously low levels. Calcium is very important for the body as well. Calcium controls the contractions of muscles, the firing of the nerves, and many other vital functions. Low calcium levels (hypocalcemia) may cause tremors, muscle spasms (tetany), seizures, vomiting, and abnormal rhythms of the heart.

Hypoparathyroidism is usually discovered in the children with a 22q11.2 deletion at birth or shortly thereafter. Sometimes, the finding of a low calcium level is what causes the doctors to order the test to diagnose the 22q11.2 deletion. The hypoparathyroidism that occurs in the newborn period may only be temporary, but there are reports of recurrences of hypoparathyroidism later in childhood. Most likely, these children had mild hypoparathyroidism that persisted and went undetected, but an intervening illness tipped them over the edge. Children with the 22q11.2 deletion who have normal calcium levels at birth do not generally go on to develop hypoparathyroidism later.

Hypoparathyroidism is diagnosed by a blood test. The best way to diagnose this problem is to find a low PTH level at the time when the calcium level is low. You may hear about different tests for calcium: total and ionized. Most of the calcium in the bloodstream is attached to proteins. Total calcium measures just that: all of the calcium in the blood, the part attached to proteins and the part that travels freely. Ionized calcium is a measure of just that free portion not attached to proteins. The ionized calcium is a more accurate measure of what is going on in the body, but except for very sick children and in some special situations, the total calcium is a very good measure as well.

If your child is diagnosed with hypoparathyroidism, he or she will need to take special medications to help keep the calcium levels in the body at a safe level. PTH is not given to children, but the calcium levels can be kept normal with a special kind of Vitamin D (not the kind found in milk and in the health food stores). He or she will need to periodically see a paediatric endocrinologist and have the calcium levels checked with a blood test.

Immune System