An eight-year-old Hispanic boy presented with persistent palpitations. Past medical history included asthma, myopia, hypothyroidism, and speech delay. Family history was unremarkable for muscular dystrophies, cardiomyopathy, arrhythmias, or sudden cardiac death. On physical examination, he was hemodynamically stable. A grade 3/6 pansystolic murmur along the left lower sternal border was appreciated. Interestingly, no skeletal muscle disease was appreciated as the patient had 5/5 strength present bilaterally in upper and lower extremities.\nPertinent labs () included elevated brain natriuretic peptide (average 5228 ± 3660 pg/mL; normal <100 pg/mL), elevated creatine kinase (average 649 ± 105 U/L; normal 94–499 U/L), elevated AST (average 363 ± 44 U/L; normal 10–40 U/L), and elevated ALT (average 225 ± 47 U/L; normal 7–56 U/L) levels. No troponin levels were reported. Electrocardiogram (ECG) showed a Wolf-Parkinson-White (WPW) with a left bundle branch block pattern, and peaked QRS complexes consistent with hypertrophic cardiomyopathy (). Echocardiogram revealed hypertrophic cardiomyopathy (HCM) with initial septal thickness of 26 mm.
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.