Vitamin D-Dependent Rickets Type 1
What is Vitamin D-Dependent Rickets Type 1?
Vitamin D-Dependent Rickets Type 1 is a rare genetic condition that affects how your body uses vitamin D. Your body needs vitamin D to absorb calcium and build strong bones. In this condition, your body cannot convert vitamin D into its active form.
The problem starts with a missing or faulty enzyme called 1-alpha-hydroxylase. This enzyme normally changes vitamin D from your diet and sunlight into the active form your bones need. Without it, your bones cannot get enough calcium. This leads to soft, weak bones that bend and break easily.
This condition usually appears in infancy or early childhood. It is inherited, meaning it passes from parents to children through genes. Early diagnosis and treatment can prevent serious bone problems and help children grow normally.
Symptoms
- Bowed legs or knock knees that develop as children start walking
- Delayed walking or difficulty standing without support
- Bone pain or tenderness in the legs, pelvis, or spine
- Muscle weakness and low muscle tone
- Slowed growth and short stature for age
- Delayed tooth development or dental problems
- Fractures that happen with minor injuries
- Widened wrists or ankles due to bone changes
- Soft spots on the skull that stay open longer than normal
- Irritability and restlessness in infants
Symptoms typically begin between 2 months and 2 years of age. Without treatment, bone deformities become more severe over time.
Concerned about Vitamin D-Dependent Rickets Type 1? Check your levels.
Screen for 1,200+ health conditions
Causes and risk factors
Vitamin D-Dependent Rickets Type 1 is caused by mutations in the CYP27B1 gene. This gene provides instructions for making the 1-alpha-hydroxylase enzyme. When the gene is faulty, your body cannot produce enough working enzyme. Without this enzyme, vitamin D stays inactive and cannot help your bones absorb calcium.
The condition follows an autosomal recessive inheritance pattern. This means a child must inherit one faulty gene from each parent to develop the condition. Parents who carry one faulty gene typically have no symptoms. If both parents are carriers, each child has a 25 percent chance of inheriting the condition. Family history is the primary risk factor for this rare genetic disorder.
How it's diagnosed
Doctors diagnose Vitamin D-Dependent Rickets Type 1 through blood tests, X-rays, and genetic testing. Blood work shows low calcium levels, high parathyroid hormone, and high alkaline phosphatase. Vitamin D testing reveals normal or slightly low levels of 25-hydroxyvitamin D, but very low levels of the active form called 1,25-dihydroxyvitamin D.
Rite Aid offers vitamin D testing through our add-on test at Quest Diagnostics locations nationwide. Testing your 25-Hydroxy Vitamin D levels is the first step in understanding your vitamin D status. If results suggest a problem with vitamin D metabolism, your doctor may order additional specialized tests. X-rays can show bone changes like widened growth plates, bowing, or fractures. Genetic testing can confirm the diagnosis by identifying mutations in the CYP27B1 gene.
Treatment options
- Daily calcitriol, the active form of vitamin D, prescribed by your doctor
- Calcium supplements to ensure adequate calcium intake
- Regular blood tests to monitor calcium and vitamin D levels
- Phosphate supplements if blood phosphate levels are low
- Diet rich in calcium from dairy products, leafy greens, and fortified foods
- Physical therapy to strengthen muscles and improve mobility
- Orthopedic care for severe bone deformities or fractures
- Lifelong medical monitoring to adjust treatment as needed
Need testing for Vitamin D-Dependent Rickets Type 1? Add it to your panel.
- Simple blood draw at your nearest lab
- Results in days, not weeks
- Share results with your doctor
Frequently asked questions
Regular rickets is caused by not getting enough vitamin D from diet or sunlight. Vitamin D-Dependent Rickets Type 1 is a genetic condition where your body cannot activate vitamin D, even when levels are normal. This genetic form requires treatment with the active form of vitamin D, not just regular vitamin D supplements. Regular rickets usually responds well to vitamin D and calcium alone.
This condition follows an autosomal recessive pattern. A child must inherit one faulty gene from each parent to develop the condition. If both parents carry the gene, each child has a 25 percent chance of having the condition. Parents who are carriers typically have no symptoms and may not know they carry the gene until a child is diagnosed.
There is no cure for this genetic condition, but it can be managed very effectively with lifelong treatment. Daily calcitriol and calcium supplements can prevent bone problems and allow normal growth. With proper treatment started early, most children develop normally and live healthy lives. Treatment must continue throughout life to maintain bone health.
Symptoms typically begin between 2 months and 2 years of age. Early signs may include muscle weakness, irritability, or delayed motor milestones. As children start to walk, bowed legs or other bone deformities may become noticeable. Early diagnosis and treatment are important to prevent permanent bone damage.
Untreated rickets leads to severe bone deformities, frequent fractures, and stunted growth. Children may develop permanently bowed legs, spinal curvature, or pelvic deformities. Low calcium can cause muscle spasms, seizures, or heart problems. With treatment, these serious complications can be prevented, and most children develop normally.
After diagnosis, children need frequent blood tests to monitor calcium and vitamin D levels. During the first few months of treatment, testing may occur every 2 to 4 weeks. Once levels are stable, testing typically happens every 3 to 6 months. Regular monitoring helps doctors adjust medication doses as your child grows.
This is a genetic condition present from birth, though diagnosis sometimes occurs later in childhood. Adults who had the condition as children need lifelong treatment. Rarely, mild cases may go undiagnosed until adulthood, causing bone pain and fractures. If you had unexplained bone problems as a child, genetic testing may provide answers.
Most children do not need surgery if treatment starts early. Calcitriol and calcium can prevent bone deformities from developing or worsening. If severe deformities exist before treatment begins, orthopedic surgery may be needed once bones are stronger. Early diagnosis gives the best chance to avoid surgery entirely.
Focus on calcium-rich foods like milk, yogurt, cheese, and fortified plant milks. Leafy greens, canned fish with bones, and fortified cereals also provide calcium. Your child will need calcitriol medication regardless of diet because the condition prevents vitamin D activation. A balanced diet supports overall health and works alongside medical treatment.
Yes, siblings should be evaluated because they may carry the same genetic mutations. If parents are confirmed carriers, each sibling has a 25 percent chance of having the condition. Early testing allows for prompt treatment if needed. Genetic counseling can help families understand inheritance risks and testing options for family members.