Hereditary Hypophosphatasia is due to a deficiency in tissue-nonspecific alkaline phosphatase (TNSALP). The manifestations may range from mild to severe.

Inheritance may be autosomal recessive or dominant.


Clinical features:

(1) failure to thrive

(2) short stature

(3) pathologic fractures

(4) bone pain

(5) craniosynostosis

(6) impaired vitamin B6 metabolism with vitamin B6 responsive seizures

(7) nephrocalcinosis

(8) delayed walking

(9) waddling gait

(10) premature loss of primary teeth with intact roots


Laboratory findings:

(1) persistently low serum alkaline phosphatase activity for age

(2) elevated serum pyridoxal-5'-phosphate (PLP)

(3) elevated urine phosphoethanolamine (PEA)

(4) normal or elevated serum calcium with hypercalciuria


Imaging studies:

(1) poor bone mineralization

(2) radiolucent projections from the epiphyseal plate into the metaphysis

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