Genetic Causes
Hypophosphatasia is caused by mutations in the ALPL gene. This gene is responsible for producing an enzyme called tissue-nonspecific alkaline phosphatase (TNSALP). This enzyme plays a critical role in the mineralization process, which makes bones and teeth hard and strong. When the gene is mutated, the body produces low levels of the enzyme or produces an enzyme that does not function correctly. As a result, substances like inorganic pyrophosphate accumulate in the body and block calcium and phosphorus from depositing into the bones. This leaves bones soft and prone to deformity, a condition chemically similar to rickets but caused by an enzyme defect rather than a vitamin deficiency.

Inheritance Patterns
The condition is inherited in one of two ways, depending on the specific form. Severe forms, such as those appearing before or shortly after birth, are typically inherited in an autosomal recessive pattern, meaning a child must inherit two non-working copies of the gene (one from each parent). Milder forms, such as those appearing in adulthood or affecting only the teeth, can be inherited in an autosomal dominant pattern (requiring only one mutated gene) or an autosomal recessive pattern. Family history is the primary risk factor for developing the condition.

Prevention
Because Hypophosphatasia is a genetic disorder, there are no lifestyle changes or vaccines that can prevent the condition from occurring. Primary prevention is limited to genetic counseling for prospective parents who have a family history of the disease or are known carriers of the ALPL gene mutation. Counseling allows families to understand the risks of passing the condition to their children. There are no known environmental triggers that cause the mutation itself.

Common Signs and Symptoms
Symptoms vary significantly depending on the age of onset and the severity of the mutation. A hallmark sign across many age groups is the premature loss of baby teeth, often before age five, where the tooth falls out with the root fully intact. In infants and young children, symptoms may include soft skull bones (craniotabes), widened wrist and ankle joints, bowed legs, and a misshapen chest which can lead to breathing problems. Infants may also fail to gain weight and thrive. In adults, the condition often presents as recurring fractures (especially in the feet or thigh bones), chronic muscle and joint pain, and a history of dental issues. Some individuals may have a form called Odontohypophosphatasia, which affects only the teeth.

Diagnostic Tests
Clinicians identify Hypophosphatasia primarily through blood tests that measure the level of alkaline phosphatase (ALP). A consistently low ALP level is the key indicator, although this is sometimes overlooked or mistaken for a normal variation if age-specific reference ranges are not used. Doctors also test for elevated levels of Vitamin B6 (pyridoxal 5'-phosphate) in the blood, as the body cannot process it properly without the ALP enzyme. Imaging tests, such as X-rays, are used to look for characteristic bone changes like poor mineralization, bowing, or specific fracture patterns. Genetic testing for mutations in the ALPL gene confirms the diagnosis.

Differential Diagnosis
Hypophosphatasia is frequently misdiagnosed because its symptoms resemble other bone disorders. It is most often confused with nutritional rickets (caused by Vitamin D deficiency), osteoporosis, or Osteogenesis Imperfecta (brittle bone disease). Distinguishing it from these conditions is vital because standard treatments for osteoporosis, such as bisphosphonates, can be harmful to patients with Hypophosphatasia.

Medications and Enzyme Replacement
The primary treatment for the underlying cause of Hypophosphatasia, particularly in patients with pediatric-onset disease, is enzyme replacement therapy (asfotase alfa). This medication replaces the missing alkaline phosphatase enzyme, helping to improve bone mineralization and respiratory function. It has significantly altered the course of the disease for many patients, improving survival and mobility. For pain management, non-steroidal anti-inflammatory drugs (NSAIDs) may be used under medical supervision.

Surgical and Supportive Care
Management often requires a multidisciplinary approach. Orthopedic surgery may be necessary to stabilize fractures using metal rods (rodding) rather than plates, as the soft bone may not hold screws well. Dental care is crucial to preserve teeth as long as possible; dentures or implants may be required for adults. Physical and occupational therapy are used to maintain muscle strength and mobility. In infants with skull deformities (craniosynostosis), surgery may be needed to relieve pressure on the brain.

Contraindications and Monitoring
It is critical to avoid bisphosphonates, a common class of bone drugs, as they can worsen the condition by further inhibiting mineralization. Vitamin D and calcium supplements should also be used with caution and only if a deficiency is proven, as patients with Hypophosphatasia are at risk for developing hypercalcemia (high calcium levels in the blood) and kidney calcification. Regular monitoring of kidney function and calcium levels is standard.

When to Seek Medical Care
Patients should see a doctor if they experience unexplained bone pain, recurrent fractures, or loose teeth. Emergency care is needed for severe breathing difficulties in infants or acute fracture pain. Routine follow-up is essential to monitor for complications such as kidney calcification (nephrocalcinosis) or ectopic calcification (calcium deposits in the eyes or joints).

Severity Levels
The severity of Hypophosphatasia represents a broad spectrum. The perinatal form is the most severe and was historically almost always fatal due to respiratory failure caused by a small, soft rib cage. The infantile form presents in the first six months of life and can also be life-threatening without treatment. Childhood and adult forms are generally less severe regarding survival but are associated with significant morbidity, including chronic pain, recurrent fractures, and mobility limitations. The mildest form, Odontohypophosphatasia, affects only the teeth.

Complications and Long-Term Effects
Short-term complications in severe cases include seizures (responsive to Vitamin B6) and respiratory distress. Long-term health risks involve chronic bone pain, muscle weakness, and difficulties with walking. A significant complication is nephrocalcinosis, where calcium deposits form in the kidneys, potentially leading to reduced kidney function. Adults often suffer from slow-healing fractures, particularly stress fractures in the metatarsal bones of the feet or the femur.

Prognosis
The introduction of enzyme replacement therapy has dramatically improved the prognosis for severe forms of the disease, allowing many infants who would have previously succumbed to respiratory failure to survive and grow. For adults and those with milder forms, life expectancy is typically not affected, but the condition can impose a substantial burden on quality of life due to physical limitations and pain. Early diagnosis and appropriate management prevent harmful mistreatments and mitigate complications.

Daily Activities and Mobility
Living with Hypophosphatasia often involves managing fatigue and physical limitations. Adults and children may experience muscle weakness or pain that makes walking distances or performing high-impact activities difficult. Adaptive devices, such as orthotics for the feet or mobility aids, can help maintain independence. Children may require modifications at school, such as exemption from certain physical education activities or extra time to move between classes.

Mental and Emotional Health
Chronic pain and the stress of managing a rare, lifelong condition can impact mental health. Patients may feel isolated due to the rarity of the disease. Connecting with patient support groups and advocacy organizations can provide valuable emotional support and practical advice from others facing similar challenges.

Questions to Ask Your Healthcare Provider
Being prepared for appointments helps ensure you get the best care. Consider asking the following questions:

• What specific form of Hypophosphatasia do I (or my child) have?
• Are there any medications or supplements I should strictly avoid?
• How often do I need monitoring for kidney calcium deposits?
• Is enzyme replacement therapy appropriate for my specific case?
• What are the risks of passing this condition to future children?
• Can you recommend a dentist familiar with this condition?

Q: Is Hypophosphatasia the same as rickets?
A: No. While the symptoms like bowed legs are similar, rickets is usually caused by a lack of Vitamin D or calcium. Hypophosphatasia is a genetic metabolic disorder caused by an enzyme deficiency, and treating it with standard rickets therapy (high dose Vitamin D) can be harmful.

Q: Can adults develop Hypophosphatasia later in life?
A: Adults do not develop the condition later in life; they are born with the genetic mutation. However, symptoms may be mild and go unnoticed until adulthood, when they present as stress fractures, foot pain, or early tooth loss.

Q: Is there a cure for this condition?
A: There is currently no complete cure that fixes the genetic mutation. However, enzyme replacement therapy is an effective treatment that addresses the underlying enzyme deficiency, significantly improving bone health and survival in severe cases.

Q: Why is low alkaline phosphatase (ALP) often ignored in blood tests?
A: Low ALP is much less common than high ALP (which signals liver or bone disease). Routine lab reports often flag only high values as abnormal. Consequently, a low result is frequently disregarded by clinicians not looking for it, leading to diagnostic delays.

Q: Can I take calcium supplements to strengthen my bones?
A: You should only take calcium if your doctor specifically prescribes it. In Hypophosphatasia, calcium cannot properly enter the bones and may build up in the blood or kidneys, causing kidney stones or other damage.