A case report of delayed diagnosis of danon disease: Caused by a newly recognized mutation in the lysosome-associated membrane protein-2 gene

INTRODUCTION: Danon disease is a rare X-linked dominant genetic disorder caused by defects in the lysosome-associated membrane protein 2 (LAMP2) gene. Unless treated, cardiogenic death is the main cause of mortality. This case report describes a 19-year-old man who was diagnosed with Danon disease and survived for 3 years from symptom onset to death. The mutation in his LAMP2 gene (p.Gly221Ilefs∗19) had not been previously reported. PATIENT CONCERNS: A 19-year-old man patient was hospitalized for intermittent palpitations. He had no family history of cardiomyopathy, arrhythmia, or sudden cardiac death, but his sister had died of cirrhosis at age 12 years, but the exact cause of cirrhosis was unknown. DIAGNOSIS: Exome sequencing and Sanger sequencing identified a novel missense mutation (p.Gly221Ilefs∗19) in the LAMP2 gene of the proband. This mutation was also detected in his mother, confirming the diagnosis of Danon disease. INTERVENTIONS: The patient experienced various types of arrhythmia throughout the clinical process, including Wolff–Parkinson–White syndrome, non-sustained atrial tachycardia, atrial flutter, and third-degree atrioventricular block. He was therefore treated with cardiac ablation procedures and cardiac resynchronization therapy. OUTCOMES: The period from the onset of symptoms to the onset of heart failure was 2 years. The patient died of cardiogenic death during the third year, at age 22 years. LESSONS: Danon disease is a rare disease that is difficult to recognize because of its hidden early manifestations. Early identification of its clinical symptoms can lead to early diagnosis and treatment.