Hypophosphatasia is a rare metabolic bone disease caused by a mutation that leads to low levels of alkaline phosphatase and impaired bone mineralization. It is inherited in an autosomal recessive pattern and results in similar manifestations to rickets, including bowed legs, short stature, abnormal tooth development, and loss of teeth. Imaging shows abnormal bone formation and deossification near growth plates. Labs show decreased alkaline phosphatase in serum and diagnostic phosphoethanolamine in urine. There is no approved treatment currently, though phosphate therapy is being investigated.

1. HYPOPHOSPHATASIA
DR.ZAMIN ABBAS
RESIDENT ORTHOPAEDIC SURGEON

2. • a metabolic bone disease caused by
a mutation in the isoenzyme of alkaline
phosphatase .
• leads to low levels of alkaline phosphate and
generalized impairment of bone
mineralization.

3. Epidemiology
• Incidence
estimated to be 1 in 100,000

4. Etiology
• Pathophysiology
• low levels of alkaline phosphate
• result in decreased synthesis of inorganic phosphate
necessary for bone matrix formation
• osteoid that forms in the hypertrophic zone of the growth
plate fails to mineralize
• the zone of provisional calcification never forms and
growth is inhibited

5. Genetics
• inheritance pattern
autosomal recessive
• caused by a mutation in the tissue-nonspecific
isoenzyme of alkaline phosphatase (TNSALP)

6. Associated conditions
orthopaedic manifestations
• similar to rickets
• bow legs (GENU VARUM)
• short stature
non-orthopaedic manifestations
• abnormal tooth formation
• loss of teeth

8. Imaging
Radiograph findings
• abnormal bone
formation
• "deossification of bone"
adjacent to growth
plate
• physeal widening

9. Labs
serum
• decreased serum alkaline phosphatase
urine
• phosphoethanolamine in the urine diagnostic
for hypophosphatasia

11. Treatment
• Nonoperative
• no approved therapies
• phosphate therapy under investigation but
not utilized at this time

12. Thank you