Symptoms of HPP can appear at any age, from birth to adulthood, and can have a mild to significant impact on daily life, depending on the severity of the condition. HPP impairs the mineralization, or calcification, of teeth and bones, which can lead to tooth loss and bones that are too soft and prone to fracture or deformed.

How HPP Symptoms Can Vary

The severity of HPP is different from one person to the next, partly because it can be inherited in different ways and the mutation can affect people differently. That means that even among family members who test positive for the gene, the onset, symptoms, and severity may differ. “HPP is caused by a variant in the ALPL gene, and it can be transmitted both in an dominant and recessive fashion,” says Kathyrn Dahir, MD, a physician in the Vanderbilt University Medical Center and a professor of medicine in the division of diabetes and endocrinology at Vanderbilt University Medical Center (VUMC) in Nashville, Tennessee. “People with two gene mutations — one from Mom and one from Dad — tend to have more severe disease, while those with one mutation or autosomal dominant tend to have a milder version that presents later in life.” Children who develop HPP in the womb or in the first few months of life often have the most severe symptoms, such as seizures and an unformed rib cage and lungs, according to Jill Simmons, MD, a pediatrician and professor of pediatrics in the division of pediatric endocrinology and diabetes at VUMC. Both Dr. Simmons and Dr. Dahir are leading experts on this rare condition. Here’s a closer look at some of the signs and symptoms of HPP. In infants, they can include:

Short limbsAbnormally shaped chestSoft skull bonesPoor feedingInability to gain weightBreathing problemsElevated levels of calcium in the blood, which can cause vomiting and kidney problems

In children and adults, they can include:

Premature loss of baby teethShort statureBowed legsKnock-knees, where the knees bend inward toward each other, even when the feet are spaced apartEnlarged wrist and ankle jointsAbnormal skull shapeSoftening of the bonesRecurring fractures, especially in the foot and thigh bonesChronic pain from fractures and inflammation in the jointsLoss of adult teeth

  1. Work with a team of specialists. Because HPP has a myriad of symptoms and complications, treatment requires a multidisciplinary team. This can include a mix of the following: pediatrician, endocrinologist, geneticist, rheumatologist, orthopedic surgeon, periodontist or oral surgeon, genetic counselor, and pain management specialist. Regular dental care beginning early on is recommended, too. As kids with HPP become adults (around age 18 to 21), Simmons says, “Transition programs are important from a pediatric clinic to an adult clinic, so they learn how to manage their disease on their own.”
  2. Take advantage of physical and occupational therapy. Depending on how much mobility is affected by HPP, devices such as a cane, walker, or wheelchair can help, as can home modifications such as a wheelchair ramp. “It’s crucial to work with a specialized physical therapist or occupational therapist to help you identify what your needs are and also to work with a physical therapist on strength and conditioning,” says Dahir. “I really can’t underscore [enough] the importance of working with a skilled physical therapist throughout your entire life.”
  3. Take steps to protect bone health. While it may seem like calcium or vitamin D supplements would be important with HPP, Simmons says this is not necessarily the case. “Those with HPP need to consume a normal amount of vitamin D and calcium, just like somebody without hypophosphatasia,” she says. Recommendations are generally 1,000 milligrams (mg) per day of calcium and 600 international units (IU) of vitamin D. For women after menopause, the calcium goal increases to 1,200 mg a day. In addition, doing weight-bearing exercises as much as you (or your child) can tolerate helps strengthen bones, too. It’s also important to avoid a class of osteoporosis drugs called bisphosphonates, which may worsen HPP, according to the National Organization for Rare Disorders (NORD). This can be a problem in adults, because HPP is sometimes misdiagnosed as osteoporosis, Dahir says.
  4. Talk to your doctor about medications. If diagnosed before age 18, enzyme replacement therapy can be an option to lessen symptoms. Because bone pain is common in HPP, nonsteroidal anti-inflammatories (NSAIDs) may help as well, although they require caution and monitoring to make sure they’re not used too much or for too long.
  5. Seek out resources and support. There are several resources that Dahir and Simmons recommend. For education on HPP, visit NORD and the Genetic and Rare Diseases Information Center. The MAGIC Foundation is a nonprofit focused on support services for families affected by conditions that affect a child’s growth, including HPP. And Soft Bones offers community support for families affected by HPP. A genetic counselor or mental health professional may be helpful as well. While HPP is often a challenge for individuals and families, management, support, and working with a team of specialists can make a big difference.