ESPE Abstracts

Introduction: Alkaline Phosphatase (ALP) is an enzyme produced mainly by the liver and bones. Several conditions such as vitamin deficiencies or hypothyroidism can impair ALP synthesis and lead to low serum levels. Low levels can also be caused by rarer conditions such as hypophosphatasia. We noticed low levels of ALP in several of our patients with Duchenne Muscular Dystrophy (DMD) and wondered if this could be caused by low bone turnover due to high dose steroids.

Methods: This was an observational study including boys under 18 years of age with DMD in South Wales. We evaluated the data from case records available on “Welsh Clinical Portal”. We analysed serum ALP levels as per our laboratories’ normal ranges within various age groups. We also evaluated the usage of continuous vitamin D supplements (one of the audit criteria recommended by the North Star network).

Results: Our sample size included 37 boys (mean age 12.5 years). The average age of initiation of steroid treatment was 6 years. Out of 37 boys, 22 had ALP measured before starting steroid therapy and of these 77.3% (17/22) had low ALP prior to starting steroids. The mean ALP for them was 130.3 IU/L, normal range being 156-369 IU/L. Twenty-five boys were started with prednisolone, six with deflazacort, three switched from prednisolone to deflazacort later and three never received steroids. In 2 out of 5 boys with initial normal levels, ALP levels significantly reduced after starting steroid therapy. The mean Vitamin D level at the first analysis was 41.2 nmol/L with everyone receiving daily vitamin D supplements thereafter.

Conclusion: Within the cohort of DMD boys in South Wales the majority who had ALP measured pre and post initiation of high dose steroids had lower ALP levels before initiating steroid therapy, other causes of low ALP levels were not excluded before starting steroids. This therefore contradicts our theory of steroids as a causation. In 2 boys the initiation of steroids could be implicated in reducing ALP. The literature regarding ALP levels in DMD is quite scarce and our study shows low ALP levels in DMD which is contrary to a study by Zhu et al which suggested that ALP levels are raised in DMD. We have been unable to identify the reason for the low levels and would recommend further studies to evaluate the aetiology of low alkaline phosphatase in Duchenne Muscular Dystrophy.