Danon disease is an underdiagnosed cause of advanced heart failure in young female patients: a LAMP2 flow cytometric study.

AIMS: Danon disease (DD) is a rare X-linked disorder caused by mutations in the lysosomal-associated membrane protein type 2 gene (LAMP2). DD is difficult to distinguish from other causes of dilated or hypertrophic cardiomyopathy (HCM) in female patients. As DD female patients regularly progress into advanced heart failure (AHF) aged 20-40 years, their early identification is critical to improve patient survival and facilitate genetic counselling. In this study, we evaluated the prevalence of DD among female patients with non-ischemic cardiomyopathy, who reached AHF and were younger than 40 years. METHODS AND RESULTS: The study cohort comprised 60 female patients: 47 (78%) heart transplant recipients, 2 (3%) patients treated with ventricular assist device, and 11 (18%) patients undergoing pre-transplant assessment. Aetiology of the cardiomyopathy was known in 15 patients (including two DD patients). LAMP2 expression in peripheral white blood cells (WBC) was tested by flow cytometry (FC) in the remaining 45 female patients. Whole exome sequencing was used as an alternative independent testing method to FC. Five additional female DD patients (two with different novel LAMP2 mutations) were identified by FC. The total prevalence of DD in this cohort was 12%. HCM phenotype (57% vs. 9%, * P = 0.022) and delta waves identified by electrocardiography (43% vs. 0%, ** P = 0.002) were significantly more frequent in DD female patients. CONCLUSIONS: Danon disease is an underdiagnosed cause of AHF in young female patients. LAMP2 expression testing in peripheral WBCs by FC can be used as an effective screening/diagnostic tool to identify DD in this patient population.

Prevalence and clinical characteristics of Danon disease among patients with left ventricular hypertrophy and concomitant electrocardiographic preexcitation.

BACKGROUND: Cardiac involvement in Danon disease typically manifests as left ventricular hypertrophy (LVH) and ventricular preexcitation. This study aimed to identify patients with Danon disease among patients with LVH and concurrent electrocardiographic preexcitation. METHODS: Electrocardiographic preexcitation was identified in 10 of 197 patients with unexplained LVH in whom genetic testing was performed using next-generation sequencing. RESULTS: Three (3/10, 30%) patients with Danon disease were found in association with different mutations in the gene of lysosome-associated membrane protein 2 (LAMP2). Compared to seven patients without Danon disease, these three patients presented with distinctive clinical phenotypes, including onset at an earlier age (20 ± 2 years vs. 53 ± 9 years, p < 0.001), more neurological involvements (100% vs. 0, p = 0.008), higher electrocardiographic voltages (10 ± 1 mV vs. 5 ± 1 mV, p < 0.001), wider QRS complexes (163 ± 5 ms vs. 115 ± 20 ms, p = 0.006), less common asymmetric hypertrophy (0% vs. 86%, p = 0.033), and more frequent elevation of three serum enzymes (creatine kinase, aspartate aminotransferase, and lactate dehydrogenase). Intracellular vacuoles accumulation with deficiencies of LAMP2 protein was found in both cardiac and skeletal myocytes of patients with Danon disease. CONCLUSION: In patients with coexistent LVH and ventricular preexcitation, Danon disease is common with distinctive clinical presentations. Comprehensive assessment of these resemble patients can provide valuable findings for early identification and clinical decision making of patients with Danon disease.

Danon disease: Gender differences in presentation and outcomes.

BACKGROUND: Danon disease (DD) is a rare X-linked autophagic vacuolar myopathy, characterized by high penetrance and severe cardiomyopathy. Because of its rarity, the natural history (NH) is uncertain. OBJECTIVES: We aimed to describe disease variability and outcomes through a systematic review of all published DD cases. METHODS: Among 83 manuscripts in MEDLINE and EMBASE on DD cases published until October 2017, we identified 146 patients with positive genetic testing for DD or positive muscle biopsy in a relative of a genetically diagnosed proband. RESULTS: 56 females and 90 males were identified. 92.5% of patients had cardiac abnormalities. Females presented with either hypertrophic cardiomyopathy (HCM, 70.3%) or dilated cardiomyopathy (DCM, 29.3%) whereas males presented with HCM 96.2% of the time. The composite outcome of death, heart transplant or ventricular assist devices occurred equally in both sexes (32% of females and 37% of males, p = 0.60) but later in females (median age 38 years) than in males (median age 21 years, p < 0.001). Whereas women present with isolated cardiac disease 73% of the time, in males DD was frequently multisystemic and presented as a triad of cognitive impairment, skeletal myopathy, and HCM in 42% of patients. CONCLUSIONS: In this first systematic review of DD, we confirmed the severe morbidity and mortality associated with disease in both sexes. Women presented with both HCM and DCM and generally with isolated cardiac disease, whereas in men DD usually presented as HCM and was frequently multi-systemic. Further prospective NH studies will be required to confirm these findings.

A Nationwide Survey on Danon Disease in Japan.

Danon disease, an X-linked dominant cardioskeletal myopathy, is caused by primary deficiency of lysosome-associated membrane protein-2 (LAMP-2). To clarify the clinicopathological features and management, we performed the first nationwide, questionnaire-based survey on Danon disease in Japan. A total of 39 patients (17 males, 22 females) from 20 families were identified in the analysis. All patients had cardiomyopathy. Of the 21 patients who died, 20 (95%) died of cardiac failure or sudden cardiac arrest. Most patients had hypertrophic cardiomyopathy. Wolf⁻Parkinson⁻White syndrome was present at a comparatively high incidence (54% in males, 22% in females). Only one female patient received a heart transplant, which is the most effective therapy. Histopathologically, all male patients showed autophagic vacuoles with sarcolemmal features in muscle. Half of the probands showed de novo mutations. Male patients showed completely absent LAMP-2 expression in muscle. In contrast, female patients showed decreased LAMP-2 expression, which is suggested to reflect LAMP-2 haploinsufficiency due to a heterozygous null mutation. In conclusion, Danon disease is an extremely rare muscular disorder in Japan. Cardiomyopathy is the most significant prognostic factor and the main cause of death. Our findings suggest that the present survey can extend our understanding of the clinical features of this rare disease.

Natural history of Danon disease.

BACKGROUND: Danon disease is a rare but serious cardiac and skeletal myopathy leading to substantial morbidity and early mortality due to arrhythmia and cardiomyopathy. The X-linked nature of inheritance accounts for reported differences in phenotypic severity between men and women. The rarity of Danon disease has limited understanding of the complete phenotype. Clinical estimates of ages of disease onset and survival based on gender have not been published. METHODS AND RESULTS: We present data on 82 patients with Danon disease from 36 families, the largest series to date. Men were severely affected with cognitive disabilities (100%), hypertrophic cardiomyopathy (88%), and muscle weakness (80%). Men had a high morbidity and were unlikely to reach the age of 25 years without a cardiac transplantation. Women were less severely affected but reported higher than expected levels of cognitive (47%) and skeletal muscle complaints (50%) and manifesting an equal prevalence of dilated cardiomyopathy and hypertrophic cardiomyopathy. Combining our data with that of 63 other Danon disease case reports in the literature, the average ages of first symptom, cardiac transplantation, and death were 12.1, 17.9, and 19.0 years in men and 27.9, 33.7, and 34.6 years in women, respectively. CONCLUSION: These data more broadly illuminate the Danon disease phenotype and should prove useful to physicians working with and providing genetic counseling to families with Danon disease. Women with Danon disease present with clinical symptoms and events approximately 15 years after men and report a higher proportion of cognitive and skeletal muscle problems than previously recognized.

Clinical, electrocardiographic, and electrophysiologic characteristics of patients with a fasciculoventricular pathway: the role of PRKAG2 mutation.

BACKGROUND: The ECG, clinical, and electrophysiologic profiles of patients with a fasciculoventricular pathway are well described. Fasciculoventricular pathways occurring in the setting of glycogen storage cardiomyopathy possess unique features. OBJECTIVE: The purpose of this study was to compare the clinical, ECG, and electrophysiologic characteristics of patients with a fasciculoventricular pathway, with or without glycogen storage cardiomyopathy. METHODS: Two groups of patients with a fasciculoventricular pathway were compared: group A consisted of 10 patients with the PRKAG2 mutation (Arg302gln), and group B consisted of 9 patients without the mutation. RESULTS: Thirty percent of group A patients had left ventricular hypertrophy, and none had an additional accessory pathway. Group B patients had no structural heart disease, and 33% had an additional accessory pathway. Group A patients had a slower resting heart rate (56 ± 7 vs 75 ± 10 bpm, P <0.0001), a wider QRS complex (0.15 ± 0.01 vs 0.11 ± 0.02 ms, P = .0004), and a longer HV interval (34 ± 1 vs 25 ± 3 ms, P = .0003). During long-term follow-up, 50% of group A patients developed complete AV block versus none in group B. Eighty percent of group A patients developed atrial flutter and/or atrial fibrillation. No Group B patient had any arrhythmia during follow-up after successful ablation of additional arrhythmia circuits. No sustained ventricular arrhythmia was induced in any patient from either group. CONCLUSION: Patients with a fasciculoventricular pathway associated with the PRKAG2 mutation have distinct clinical, ECG, and electrophysiologic profiles and should be correctly identified because of their ominous long-term prognosis. Patients without the mutation have an excellent arrhythmia-free prognosis after treatment of additional circuits.