A 23-year-old man had Danon disease from the age of 12 years, when symptoms began, until 23 years old when he succumbed to his disease. He was first admitted to the Affiliated Hospital of Jining Medical University at 12 years old because of transient loss of consciousness with palpitation. He had suffered from a poor ability of physical activity, mild mental retardation, and learning difficulty. Pansystolic murmur along the left lower sternal border was not observed. Echocardiography showed HCM with a maximum left ventricular end-diastolic diameter (LVEDd) of 45 mm, left ventricular posterior wall (LVPW) thickness of 12 mm, maximum interventricular septal (IVS) thickness of 11 mm, and left ventricular ejection fraction (LVEF) of 60%. Electromyography showed normal muscle strength and deep tendon reflexes. He was diagnosed with Danon disease at 13 years of age in Beijing Union Hospital by genetic testing, which showed that he carried a deletion mutation (c.257_258delCC) in exon 3 of the LAMP-2 gene. An endomyocardial biopsy and electron microscopic examination showed autophagic vacuoles. ECG showed type B Wolff–Parkinson–White (WPW) syndrome, a high voltage in the left ventricle, and an inverted T wave (). He then underwent successful ablation in Beijing Union Hospital. He was asymptomatic for the next 3 years.\nAt the age of 17 years, he had persistent palpitations and visited the hospital. ECG () showed an ectopic rhythm, paroxysmal supraventricular tachycardia, complete left bundle branch block, and high voltage in the left ventricle. He switched to sinus rhythm following treatment with propafenone. However, an ECG () showed ventricular premature contraction. At a physical examination, a heaving apical impulse and a grade 4/6 pansystolic murmur along the left lower sternal border were observed. Follow-up echocardiography indicated that left ventricular hypertrophy of the patient progressively worsened (). MRI was performed and showed LGE in the muscular interventricular septum and the front wall of the left ventricle. However, the liver and bilateral gastrocnemius skeletal muscles were negative for LGE (). This process of cardiac hypertrophy was rapidly advancing at this stage.\nIn the next 4 years, HCM progressed to the dilated phase. The LVEDd increased from 44 to 58 mm, while the IVS decreased from 24 to 19 mm and LVPW decreased from 31 to 17 mm. The LVEF was reduced from 60% to 22% (). At the age of 23 years, an ECG () showed atrial fibrillation. An MRI () showed that gadolinium contrast enhancement was visible in the liver, psoas muscle, and bilateral gastrocnemius muscles. These abnormal findings manifested with the classic triad of cardiomyopathy, skeletal myopathy, and intellectual disability in this patient. He received an automatic implantable cardioverter-defibrillator, even after considering a heart transplant, which he refused, and he finally succumbed to his disease with sudden cardiac arrest. Unfortunately, the patient did not undergo an investigation of his device to identify the trigger for cardiac death.\nDuring the 10-year follow-up, pertinent laboratory examination values, including creatine kinase (CK), creatine kinase isoenzyme (CK-MB), hydroxybutyrate dehydrogenase, alanine aminotransferase (ALT), aspartate aminotransferase, and lactic dehydrogenase levels, were considerably elevated (). Echocardiographic data indicated that HCM had progressed into DCM ().
A Chinese boy has been followed up from 10 years old. Genetic analysis at 10 years old showed that he had Danon disease and was hemizygous for an LAMP-2 mutation, c.257_258delCC, in exon 3 of LAMP-2. Biomarker levels were also considerably elevated (CK: 1986 U/L, CK-MB: 42 U/L, ALT: 339 U/L, aspartate aminotransferase: 398 U/L, hydroxybutyrate dehydrogenase: 1080 U/L, and lactic dehydrogenase: 1151 U/L). An ECG showed high voltage in the left ventricle and an inverted T wave (), and echocardiography was normal (LVEDd, IVS, LVPW thickness, and LVEF were 48 mm, 8 mm, 8 mm, and 53%, respectively). An ECG showed WPW syndrome, a high voltage in the left ventricle, and an inverted T wave at 13 years old (). Findings at this time were similar to those in case 1 at 13 years old. Changes in the LVEDd (55 to 51 mm), IVS (15 to 21 mm), LVPW (15 to 24 mm), and LVEF (63% to 61%) were recorded in the next 2 years (), as well as changes in MRI (). However, he was too overweight to ensure good image quality. MRI showed an expanded scope of gadolinium contrast enhancement, which was visible in the myocardium. However, the liver, psoas muscle, and bilateral gastrocnemius muscles were normal. The boy was deprived of education owing to his intellectual disability. Based on these data, the boy will be followed up in the hypertrophic stage to monitor progression of HCM to DCM.