Abstract
Background: Pompe disease (PD) is a rare genetic lysosomal storage disorder that causes glycogen deposition in different body tissues/organs. Diagnosis of PD is still difficult and often delayed due to several factors as a wide clinical spectrum, overlapping of signs and symptoms with other neuromuscular disorders, and difficulties in completing the diagnostic investigations. Therefore, it was imperative to identify cases of PD amongst the high-risk population. The primary aim of this study is to determine the prevalence of late-onset PD (LOPD) among the high-risk group [patients with limb-girdle muscle weakness (LGMW) with/without HyperCKemia of unknown cause] in the Kingdom of Saudi Arabia (KSA).
Methods: A multicenter, cross-sectional screening study with an interventional diagnostic procedure (dried blood spot enzymatic activity and genetic testing) to primarily assess the prevalence of LOPD in patients with LGMW with/without HyperCKemia of unknown cause in the KSA. All eligible patients were tested after obtaining written informed consent from their parents/guardians.
Results: The analyses of this study were descriptive, and the sample size was chosen to permit the collection of sufficient data in order to determine the prevalence of LOPD in patients with LGMW with/without HyperCKemia. Consequently, the sample size has not been assessed in terms of statistical power but rather precision based on the expected frequency.
Conclusion: Despite multiple previous studies reported the incidence or prevalence of Pome disease in Saudi Arabia. Still, none of them revealed the incidence of LOPD among the high-risk group (patients with LGMW with/without HyperCKemia of unknown cause). Our screening study was the first to reveal the true numbers of LOPD among the high-risk group in Saudi Arabia, and it set a model for future studies to be conducted in the Middle-East and North Africa region.

Key words: Pompe disease, late-onset Pompe disease, LOPD, limb-girdle muscle weakness, LGMW, Saudi Arabia.