Evaluation prevalence of Pompe disease in Iranian patients with myopathies of unknown etiology.

Background: Pompe disease is a rare but potentially treatable metabolic disorder having an estimated worldwide incidence of one in forty thousand live births. While the introduction of enzyme replacement therapy (ERT) has considerably increased the awareness of the disease, the delay in diagnosis is still consistent and most patients go undetected.

Objective: This study aimed to determine the prevalence of late-onset Pompe disease (LOPD) in a high-risk population, using dried blood spot (DBS) as a main screening tool.

Methods: This cross-sectional study was performed on the 93 patients who attended to the neuromuscular center of Bu-ali hospital in Tehran, Iran, during 2014-2015. Inclusion criteria were: 1) age ≥1 years, 2) proximal myopathies of unknown etiology in lower limbs or symptoms of limb girdle muscle weakness (LGMW), and 3) unexplained elevated CPK (>174). Acid α-glucosidase (GAA) activity was measured separately on DBS by fluorometric method. For the final diagnosis, GAA deficiency was confirmed by a biochemical assay in skeletal muscle, whereas genotype was assessed by GAA molecular analysis. All statistical tests were performed using the SPSS version 16. Results are presented as mean (SD) or median (IQR), as appropriate.

Results: In a 12-month period, we studied 93 cases: 5 positive samples (5.3%) were detected by DBS screening, biochemical and molecular genetic studies finally confirmed LOPD diagnosis in 3 cases (3.22%). Among the 93 patients, 100% showed hyperCKemia, 89 patients (95.7%) showed LGMW and 4 patients had symptoms of proximal myopathies in the lower limb.

Conclusions: Results from the LOPED study suggest that GAA activity requires accurate screening by DBS in all patients referred for hyperCKemia and/or LGMW.