Clinical utility of genetic testing in the early diagnosis of Danon disease mimicking hypertrophic cardiomyopathy: A case report

Background: Danon disease (OMIM 300257) is an X-linked lysosomal storage disorder, characterized by hypertrophic cardiomyopathy (HCM), skeletal myopathy, variable intellectual disability, and other minor clinical features. This condition accounts for ~ 4% of HCM patients, with a more severe and early onset phenotype in males, causing sudden cardiac death (SCD) in the first three decades of life. Genetic alterations in the LAMP2 gene are the main cause of this inherited fatal condition. Up to date, more than 100 different pathogenic variants have been reported in the literature. However, the majority of cases are misdiagnosed as HCM or have a delay in the diagnosis. Case presentation: Here, we describe a young boy with an early diagnosis of HCM. After 2 episodes of ventricular fibrillation within 2 years, genetic testing identified a novel LAMP2 pathogenic variant. Subsequently, further clinical evaluations showing muscle weakness and mild intellectual disability confirmed the diagnosis of Danon disease. Conclusions: This report highlights the role of genetic testing in the rapid diagnosis of Danon disease, underscoring the need to routinely consider the inclusion of LAMP2 gene in the genetic screening for HCM, since an early diagnosis of Danon disease in patients with a phenotype mimicking HCM is essential to plan appropriate treatment, ie cardiac transplantation.