What ALP level is diagnostic of hypophosphatasia?

Persistently low serum ALP below the age/sex-specific lower limit of normal is required; ALP <20 IU/L in adults is strongly suggestive; elevated phosphoethanolamine and PLP (vitamin B6) are the classic biochemical findings.

What are the five forms of hypophosphatasia?

Perinatal lethal (born with severe hypomineralization, often stillborn); Infantile (features before 6 months, often fatal); Childhood (tooth loss, fractures, bone pain); Adult (stress fractures, calcium pyrophosphate arthritis); Odontohypophosphatasia (premature tooth loss only).

Why do HPP infants have pyridoxine-responsive seizures?

Tissue-nonspecific alkaline phosphatase normally dephosphorylates PLP (active B6) to allow CNS entry; without TNSALP, PLP accumulates extracellularly causing paradoxical B6 deficiency in the brain and pyridoxine-responsive seizures.

What is the dosing of asfotase alfa (Strensiq) in HPP?

Standard dose: 2 mg/kg 3x/week or 1 mg/kg 6x/week subcutaneously; higher weight-based dose for perinatal/infantile form; dramatic improvements in bone mineralization and respiratory function within weeks.

What respiratory complications occur in perinatal HPP?

Severe thoracic hypomineralization causes respiratory insufficiency from the chest being unable to expand; rib cage deformity and respiratory failure are the leading causes of death in perinatal and infantile forms.

Hypophosphatasia (HPP) Severity Classification and Asfotase Alfa Dosing

Classifies hypophosphatasia severity (perinatal/infantile/childhood/adult/odontohypophosphatasia) using ALP levels, phosphoethanolamine, PPi, TNSALP gene mutations, and asfotase alfa dosing by weight and phenotype.

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Hypophosphatasia (HPP) Severity Classification and Asfotase Alfa Dosing

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Frequently Asked Questions

What ALP level is diagnostic of hypophosphatasia?

What are the five forms of hypophosphatasia?

Why do HPP infants have pyridoxine-responsive seizures?

What is the dosing of asfotase alfa (Strensiq) in HPP?

What respiratory complications occur in perinatal HPP?