Overview
Primary hypomagnesemia with hypercalciuria and nephrocalcinosis (PHHN) — sometimes called familial hypomagnesemia with hypercalciuria and nephrocalcinosis, or FHHNC — is a rare inherited kidney disorder. In this condition, the kidneys are unable to hold onto enough magnesium and calcium, so these important minerals are lost in the urine at much higher levels than normal. Over time, the excess calcium builds up in the kidney tissue, a process called nephrocalcinosis, which can slowly damage the kidneys. The disease is caused by changes (mutations) in genes that control special channels in the kidney tubules — the tiny tubes that filter and reabsorb minerals. Without working channels, magnesium and calcium leak out instead of being kept in the body. Low magnesium levels in the blood can cause muscle cramps, spasms, and seizures. The kidneys gradually lose their filtering ability, and many patients develop chronic kidney disease over time. This specific form of PHHN is distinguished from a related condition by the absence of severe eye problems. Treatment focuses on replacing magnesium with supplements and managing kidney health. Unfortunately, supplements can slow but often cannot fully stop kidney damage. Regular monitoring by kidney specialists is essential to protect long-term kidney function.
Key symptoms:
Frequent urinary tract infectionsKidney stonesCalcium deposits in the kidneys (nephrocalcinosis)Muscle cramps and spasmsMuscle weaknessSeizures due to low magnesiumExcessive thirst and frequent urinationFatigue and low energyPoor growth or failure to thrive in childrenAbdominal or flank painGradually worsening kidney function (chronic kidney disease)
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Childhood
Begins in childhood, roughly ages 1 to 12
Treatments
No FDA-approved treatments are currently listed for Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement.
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Specialists
View all specialists →No specialists are currently listed for Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement.
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Caregiver Resources
NORD Caregiver Resources
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Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How advanced is the kidney damage right now, and how quickly might it progress?,What dose of magnesium supplement is right for my child, and how do we know if it is working?,Should we also test other family members for this condition?,Are there any dietary changes that could help protect the kidneys?,At what point would dialysis or a kidney transplant be considered?,Are there any clinical trials or new treatments we should know about?,How often should we have follow-up appointments and what tests are needed each time?
Common questions about Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement
What is Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement?
Primary hypomagnesemia with hypercalciuria and nephrocalcinosis (PHHN) — sometimes called familial hypomagnesemia with hypercalciuria and nephrocalcinosis, or FHHNC — is a rare inherited kidney disorder. In this condition, the kidneys are unable to hold onto enough magnesium and calcium, so these important minerals are lost in the urine at much higher levels than normal. Over time, the excess calcium builds up in the kidney tissue, a process called nephrocalcinosis, which can slowly damage the kidneys. The disease is caused by changes (mutations) in genes that control special channels in the
How is Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement inherited?
Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement typically begin?
Typical onset of Primary hypomagnesemia with hypercalciuria and nephrocalcinosis without severe ocular involvement is childhood. Age of onset can vary across affected individuals.