Symptoms and Signs of Hypophosphatasia
Hypophosphatasia presents with a spectrum of manifestations ranging from severe skeletal hypomineralization with rickets and respiratory failure in infants to non-specific musculoskeletal pain, fatigue, and dental problems in adults, with the hallmark finding being persistently low alkaline phosphatase activity. 1
Skeletal Manifestations
The skeletal features are the most recognized presentations:
- Rickets and osteomalacia with defective bone mineralization 1
- Bone deformities including leg deformities (varus or valgus) 1
- Pseudofractures - characteristic indicator of severely compromised enzyme activity, particularly in adults 1
- Craniosynostosis - premature fusion of cranial sutures 1
- Skeletal abnormalities and bone dysplasia 2
- Failure to thrive in infants 1
Dental and Oral Manifestations
Dental problems are frequently the presenting feature, especially in milder forms:
- Premature loss of deciduous (primary) teeth - often the first sign 1, 3
- Dental abscesses and maxillofacial cellulitis 1
- Periodontal disease 4
- Dental manifestations occur in approximately 42.6% of adult-onset cases 4
Muscular and Pain Symptoms
These non-canonical symptoms are increasingly recognized as key findings and may occur even without overt skeletal manifestations 1:
- Generalized musculoskeletal pain - reported in 52.5% of adult-onset patients 4
- Muscle weakness and muscular hypotonia 1
- Fatigue - present in 23.4% of adult-onset cases 4
- Gait disturbances and delayed motor development in children 1
- Muscular/pain symptoms reported in 79.5-100% of patients 5
Neurological Manifestations
- Vitamin B6-dependent seizures - particularly in severe infantile forms 1
- Neuropsychiatric issues 1
- Neurological signs related to craniosynostosis complications 1
Respiratory Complications
- Lung hypoplasia in severe perinatal forms 1
- Respiratory failure leading to premature death in infants 6
Other Systemic Manifestations
- Gastrointestinal issues 1
- Recurrent fractures - 22.0% of adult-onset patients 4
- Constitutional/metabolic symptoms 4
- Reduced mobility requiring use of mobility aids 5
Clinical Presentation by Age of Onset
The disease exists on a continuum 3:
Perinatal/Infantile Forms:
- Most severe presentation
- Skeletal hypomineralization
- Respiratory complications
- Seizures
- High mortality risk
Juvenile Forms:
- Bone deformities
- Delayed motor development
- Dental problems
- Growth disturbances
Adult Forms:
- Chronic bone pain (most common at 52.5%) 4
- Pseudofractures
- Dental manifestations
- Non-specific symptoms (pain, weakness, fatigue)
- Often misdiagnosed due to non-specific presentation
Critical Diagnostic Clue
The main diagnostic clue is persistently low alkaline phosphatase (ALP) activity for age and sex 2. This biochemical finding, combined with clinical manifestations and genetic confirmation of ALPL variants, establishes the diagnosis 1.
Important Clinical Pitfall
HPP is associated with substantial disease burden, including reduced mobility and quality of life, even in the absence of skeletal manifestations 5. The importance of considering HPP in patients with low ALP activity, an ALPL variant, and muscular/pain manifestations cannot be overstated, as these non-skeletal presentations are frequently overlooked 5.