Clinical and molecular findings in 44 Turkish patients with infantile-onset Pompe disease

Purpose: This study aims to investigate genotype–phenotype correlations in a cohort of 44 patients diagnosed with Infantile-onset Pompe disease (IOPD) Materials and Methods: This retrospective study analyzed the clinical and genetic characteristics of 44 Turkish infants diagnosed with IOPD between 2009 and 2025. Data on clinical presentation, GAA mutations, treatment, and outcomes were collected and evaluated. Results: The majority of patients (95.5%) presented with the classic IOPD phenotype. The mean age at symptom onset was 59.1 days, with cardiomegaly being the most common initial symptom. ERT was initiated at a mean age of 114.9 days. Despite treatment, the mortality rate remained high at 56.8%, with respiratory failure being the leading cause of death. All surviving patients exhibited improvement in cardiomyopathy; however, complications such as muscle weakness, kyphoscoliosis, and oropharyngeal dysfunction persisted. A total of 18 distinct GAA mutations were identified, including four novel variants. The most frequent mutation was p. L299P (42.9%). No definitive genotype–phenotype correlation was observed. Conclusion: These findings highlight the genetic heterogeneity and clinical complexity of IOPD in a highly consanguineous population. The high prevalence of the p.L299P mutation suggests that it may represent a founder mutation in the Turkish population..