Childhood hypophosphatasia

Other Names: Childhood-onset hypophosphatasia; Childhood-onset phosphoethanolaminuria; Childhood-onset Rathburn disease

Childhood hypophosphatasia is a form of hypophosphatasia, a rare condition that affects the bones.

Onset

Childhood hypophosphatasia, specifically, is generally diagnosed when the condition develops after six months of age but before adulthood.

Cause

Childhood hypophosphatasia is caused by changes (mutations) in the ALPL gene.

Inheritance

It can be inherited in an autosomal dominant or autosomal recessive manner.

Signs and symptoms

Signs and symptoms vary but may include delayed motor milestones; low bone mineral density for age; early loss of baby teeth (before age 5); bone and joint pain; short stature; a waddling gait; skeletal malformations; and/or unexplained broken bones. The forms of hypophosphatasia that develop during childhood are generally more mild than those that appear in infancy.

Diagnosis

The clinical variability of HPP is considerable, with the majority of findings in HPP relating either directly or indirectly to effects of TNSALP dysfunction in bone . Patients with perinatal or infantile HPP frequently manifest with severe deficit in bone mineralization, resulting in small thorax, pulmonary hypoplasia, and severe bowing of the limbs. Patients with childhood hypophosphatasia typically lack these life-threatening signs, but may still have significant disease, with poor mobility, chronic pain, and short stature . These same patients may also have significant rickets, long bone deformity, and non-traumatic fractures . Fractures which occur in patients with HPP may heal poorly and can reoccur.

Treatment

Treatment is supportive and based on the signs and symptoms present in each person. Recently an enzyme replacement therapy (ERT) called asfotase alfa has been show to improve bone symptoms in people with childhood hypophosphatasia and has been approved by the FDA.

NIH genetic and rare disease info

• NIH info on Childhood hypophosphatasia

Childhood hypophosphatasia is a rare disease.

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