Aims As of 2016, there were five patients with Pompe in Slovenia (two infantile, one childhood and two adult onset) with a prevalence of 1:400 000; however, the prevalence of late-onset Pompe disease (LOPD) in some other countries means this ratio could be an underestimate. Since an LOPD muscle biopsy could be unspecific or even normal, the purpose of this study is to assess the prevalence of LOPD in patients with non-diagnostic muscle biopsies.

Methods Six hundred biopsies were recorded at the Neuromuscular Tissue Bank of the University of Ljubljana for the period 2004–2014. All adult patients with non-diagnostic muscle biopsies were invited to the National Slovenian Neuromuscular Centre for dried blood spot testing for LOPD.

Results A total of 90 patients (56% of those invited) responded. No patient with LOPD was found. A total of 49 patients (54%) had fixed muscle weakness, 31 (34%) had mild symptoms and no weakness and 10 (11%) had asymptomatic hyperCKemia. Ventilatory insufficiency associated with proximal muscle weakness was found in two patients (2%). No patients exhibited vacuolar myopathy, globular accumulations of glycogen or regions of increased acid phosphatase activity within the sarcoplasm.

Conclusions The study results do not support the hypothesis that LOPD is underestimated in Slovenian patients with non-diagnostic muscle biopsies; this could be consistent with the fact that LOPD is of low prevalence in Slovenia, as is the case in the populations of Finland, French-speaking Belgium, west Sweden and west Denmark.