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Osteoporosis in lysinuric protein intolerance
K Parto1, R Penttinen, I Paronen
1Department of Pediatrics, University Central Hospital, University of Turku, Finland.
Journal of Inherited Metabolic Disease
|January 1, 1993
Summary
Lysinuric protein intolerance (LPI) causes osteoporosis due to defective cationic amino acid transport. Impaired collagen synthesis and increased collagen turnover contribute to bone density loss in LPI patients.
Area of Science:
- Biochemistry
- Genetics
- Orthopedics
Background:
- Lysinuric protein intolerance (LPI) is an autosomal recessive disorder affecting cationic amino acid transport.
- LPI patients exhibit a higher incidence of fractures and radiographic evidence of osteoporosis.
Purpose of the Study:
- To characterize osteopenia in patients with Lysinuric protein intolerance.
- Investigate bone metabolism, collagen synthesis, and bone structure in LPI.
Main Methods:
- Screened 29 Finnish LPI patients for bone metabolism parameters.
- Performed morphometric analysis on bone specimens from 9 patients.
- Studied collagen synthesis in cultured skin fibroblasts and measured collagen fibril sizes via electron microscopy.
Main Results:
- Histological bone analysis revealed osteoporosis in 8/9 patients; osteomalacia was excluded.
- Elevated serum free hydroxyproline and type III procollagen N-propeptide, along with increased urinary hydroxyproline, were observed in most LPI patients.
- Significantly decreased collagen synthesis in LPI fibroblasts compared to controls persisted until age 30.
Conclusions:
- Osteoporosis in LPI may stem from defective matrix protein synthesis due to protein deprivation and cationic amino acid deficiency.
- Increased collagen turnover is a potential contributing factor to osteoporosis in LPI patients.