Hypophosphatasia is characterized by defective mineralization of growing or remodeling bone, with or without root-intact tooth loss, in the presence of low activity of serum and bone alkaline phosphatase (ALP). Biallelic ALPL pathogenic variants often result in severe hypophosphatasia that can result in stillbirth without mineralized bone, while heterozygous ALPL pathogenic variants are more likely to manifest as modest, mild, or even asymptomatic disease. Regardless of the number of ALPL pathogenic variants, many individuals with hypophosphatasia suffer from pain, disability, and reduced quality of life. Variability of clinical manifestations is common in both childhood and adult forms of hypophosphatasia and even occurs within affected families. While the disease spectrum is a continuum, seven clinical forms of hypophosphatasia are usually recognized based on age at diagnosis and severity of features. Perinatal (severe): Characterized by restrictive lung disease, respiratory failure, vitamin B6-dependent seizures, hypercalcemia with high morbidity, and mortality Perinatal (benign): Prenatal skeletal manifestations that slowly resolve into one of the milder forms Infantile: Onset between birth and age six months of clinical features of rickets without elevated serum ALP activity Severe childhood (juvenile): Variable presenting features progressing to rickets Mild childhood: Present later in childhood without rachitic disease, low bone mineral density for age, increased risk of fracture, and premature loss of primary teeth with intact roots Adult: Characterized by osteomalacia and stress fractures and pseudofractures of the lower extremities in middle age, sometimes associated with early loss of adult dentition. Adults with hypophosphatasia may also have significant bone pain and pronounced non-skeletal disease, with muscle weakness, dental problems, and reduced quality of life. Odontohypophosphatasia: Characterized by premature exfoliation of primary teeth and/or severe dental caries without skeletal manifestations [from GeneReviews]
- MedGen UID:
- 120636
- •Concept ID:
- C0268413
- •
- Disease or Syndrome