Hypomagnesemia with secondary hypocalcemia

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What is hypomagnesemia with secondary hypocalcemia?

Hypomagnesemia with secondary hypocalcemia is an inherited condition caused by the body's inability to absorb and retain magnesium that is taken in through the diet. As a result, magnesium levels in the blood are severely low (hypomagnesemia).

Hypomagnesemia impairs the function of the parathyroid glands, which are small hormone-producing glands located in the neck. Normally, the parathyroid glands release a hormone that increases blood calcium levels when they are low. Magnesium is required for the production and release of parathyroid hormone, so when magnesium is too low, insufficient parathyroid hormone is produced and blood calcium levels are also reduced (hypocalcemia). The hypocalcemia is described as "secondary" because it occurs as a consequence of hypomagnesemia.

Shortages of magnesium and calcium can cause neurological problems that begin in infancy, including painful muscle spasms (tetany) and seizures. If left untreated, hypomagnesemia with secondary hypocalcemia can lead to developmental delay, intellectual disability, a failure to gain weight and grow at the expected rate (failure to thrive), and heart failure.

How common is hypomagnesemia with secondary hypocalcemia?

Hypomagnesemia with secondary hypocalcemia is thought to be a rare condition, but its prevalence is unknown.

What genes are related to hypomagnesemia with secondary hypocalcemia?

Hypomagnesemia with secondary hypocalcemia is caused by mutations in the TRPM6 gene. This gene provides instructions for making a protein that acts as a channel, which allows charged atoms (ions) of magnesium (Mg²⁺) to flow into cells; the channel may also allow small amounts of calcium ions (Ca²⁺) to pass into cells. Magnesium is involved in many cell processes, including production of cellular energy, maintenance of DNA building blocks (nucleotides), protein production, and cell growth and death. Magnesium and calcium are also required for the normal functioning of nerve cells that control muscle movement (motor neurons).

The TRPM6 channel is embedded in the membrane of epithelial cells that line the large intestine, structures in the kidneys known as distal convoluted tubules, the lungs, and the testes in males. When the body needs additional Mg²⁺, the TRPM6 channel allows it to be absorbed in the intestine and filtered from the fluids that pass through the kidneys by the distal convoluted tubules. When the body has sufficient or too much Mg²⁺, the TRPM6 channel does not filter out the Mg²⁺ from fluids but allows the ion to be released from the kidney cells into the urine. The channel also helps to regulate Ca²⁺, but to a lesser degree.

Most TRPM6 gene mutations that cause hypomagnesemia with secondary hypocalcemia result in a lack of functional protein. A loss of functional TRPM6 channels prevent Mg²⁺ absorption in the intestine and cause excessive amounts of Mg²⁺ to be excreted by the kidneys and released in the urine. A lack of Mg²⁺ in the body impairs the production of parathyroid hormone, which likely reduces blood Ca²⁺ levels. Additionally, hypomagnesemia and hypocalcemia can disrupt many cell processes and impair the function of motor neurons, leading to neurological problems and movement disorders. If the condition is not effectively treated and low Mg²⁺ levels persist, signs and symptoms can worsen over time and may lead to early death.

How do people inherit hypomagnesemia with secondary hypocalcemia?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about diagnosis or management of hypomagnesemia with secondary hypocalcemia?

These resources address the diagnosis or management of hypomagnesemia with secondary hypocalcemia and may include treatment providers.

You might also find information on the diagnosis or management of hypomagnesemia with secondary hypocalcemia in Educational resources and Patient support.

General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.

To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.

Where can I find additional information about hypomagnesemia with secondary hypocalcemia?

You may find the following resources about hypomagnesemia with secondary hypocalcemia helpful. These materials are written for the general public.

MedlinePlus - Health information (3 links)
Additional NIH Resources - National Institutes of Health
National Institute of Neurological Disorders and Stroke: Epilepsy Information Page
Educational resources - Information pages (12 links)
Patient support - For patients and families (4 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

Genetic Testing Registry - Repository of genetic test information (1 link)
PubMed - Recent literature
OMIM - Genetic disorder catalog

What other names do people use for hypomagnesemia with secondary hypocalcemia?

familial primary hypomagnesemia with hypocalcuria
HOMG
HSH
hypomagnesemic tetany
intestinal hypomagnesemia 1
intestinal hypomagnesemia with secondary hypocalcemia

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about hypomagnesemia with secondary hypocalcemia?

Ask the Genetic and Rare Diseases Information Center

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding hypomagnesemia with secondary hypocalcemia?

autosomal ; autosomal recessive ; Ca ; calcium ; cell ; channel ; developmental delay ; disability ;distal ; DNA ; epithelial ; failure to thrive ; familial ; gene ; heart failure ; hormone ; inherited ;intestine ; ions ; kidney ; motor ; neurological ; parathyroid ; prevalence ; protein ; recessive ; testes

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

References (5 links)

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook