Introduction: Hypophosphatasia (HPP) is a very rare systemic musculoskeletal disease characterised by low tissue non-specific alkaline phosphatase (ALP). The prevalence of HPP and its associated morbidity in an adult setting is unclear.
Methods: A search for serum ALP results less than 36 IU/l within NHS Greater Glasgow and Clyde between 2017 and 2018 revealed 16 280 results. A further search for patients with two ALP <36 separated by 30 days or more yielded 1143 patients over the age of 18 years. Of these, 706 patients with conditions known to be associated with low ALP were excluded (62%) as were another 129 patients who were over 80 years old. The patient characteristics of the remaining cohort were identified using electronic health care records. Rate of symptoms were calculated using the frequency of symptoms over the cumulative lifespan of patients.
Results: A total of 312 patients were identified as having persistently low ALP. 4 had an existing diagnosis of HPP (1.3%). The median age was 50 years (1880), where 64% were female and 91% of British/Scottish ethnicity. The cohort was divided into ALP quartiles and their key characteristics are summarised in the table below:
|Rate of symptoms (per10 000 person years)|
|Lowest ALP (quartiles)||N||Known HPP Diagnosis (%)||All Fractures||Dental||Psychiatric||Joint Pains||Neurological||Hearing loss|
Conclusions: Our survey has identified a sizeable number of adults who have persistently low ALP. In these cases, fractures and non-specific joint pains were the most common symptoms and similar to that reported in the global HPP registry (Högler et al, 2019). There is a need to improve the awareness as well as identification of HPP within the health care setting.
Reference: Högler et al. Diagnostic delay is common among patients with hypophosphatasia. BMC Musculoskelet Disord 2019;20(1):80.