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A moderate form of hypophosphatasia (HPP) characterized by adult onset osteomalacia, chondrocalcinosis, osteoarthropathy, stress fractures and dental anomalies.
ORPHA:247676Classification level: Subtype of disorder
- Adult Rathbun disease
- Adult phosphoethanolaminuria
- Prevalence: Unknown
- Inheritance: Autosomal dominant or Autosomal recessive
- Age of onset: Adult
- ICD-10: E83.3
- OMIM: 146300
- UMLS: C0268413
- MeSH: -
- GARD: -
- MedDRA: -
The prevalence of adult hypophosphatasia is not known. However the prevalence of moderate HPP (childhood, adult and odontoHPP) cases taken together has been estimated at 1/6300.
Adult HPP is clinically very heterogeneous. In its mildest form it is the least severe form of hypophosphatasia (HPP), characterized by non-specific symptoms in later age, such as osteoporosis, musculoskeletal pain, chondrocalcinosis. Most patients present features during middle age but some may have had a history of mild rickets or other musculoskeletal manifestations in childhood. Cardinal features include stress fractures and pseudo-fractures of the lower limbs, along with foot, thigh, and hip pain. The most common fracture types are metatarsal and tibial and femoral pseudofractures. Osteomalacia, chondrocalcinosis, and osteoarthropathy may develop with age. Some patients report history of early loss of primary dentition. Loss of permanent dentition is also common and some cases of enamel hypoplasia and tooth mobility are described. Patients with the adult form of HPP may have had some manifestations in early life between the prenatal period and childhood (prenatal benign HPP or childhood HPP). The presence of bone symptoms (osteomalacia, fractures) distinguish adult HPP from odontohypophosphatasia.
Mutations in the ALPL gene (1p36.12) are known to cause hypophosphatasia.
Diagnosis is based on clinical presentation, alkaline phosphatase assay and confirmed by genetic testing.
The main differential diagnosis is osteogenesis imperfecta.
Inheritance may be autosomal recessive (rare) or autosomal dominant (the vast majority of cases).
Management and treatment
Management is typically supportive.
Overall prognosis is typically good, although affected individuals may experience some physical limitations depending on the extent and progression of the disease.
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