Three female patients with Danon disease presenting with predominant cardiac phenotype: a case series

International Consensus on Differential Diagnosis and Management of Patients With Danon Disease: JACC State-of-the-Art Review

Danon disease is a rare X-linked autophagic vacuolar cardioskeletal myopathy associated with severe heart failure that can be accompanied with extracardiac neurologic, skeletal, and ophthalmologic manifestations. It is caused by loss of function variants in the LAMP2 gene and is among the most severe and penetrant of the genetic cardiomyopathies. Most patients with Danon disease will experience symptomatic heart failure. Male individuals generally present earlier than women and die of either heart failure or arrhythmia or receive a heart transplant by the third decade of life. Herein, the authors review the differential diagnosis of Danon disease, diagnostic criteria, natural history, management recommendations, and recent advances in treatment of this increasingly recognized and extremely morbid cardiomyopathy.

Genetic Contribution to End-Stage Cardiomyopathy Requiring Heart Transplantation

BACKGROUND

Many cardiovascular disorders propel the development of advanced heart failure that necessitates cardiac transplantation. When treatable causes are excluded, studies to define causes are often abandoned, resulting in a diagnosis of end-stage idiopathic cardiomyopathy. We studied whether DNA sequence analyses could identify unrecognized causes of end-stage nonischemic cardiomyopathy requiring heart transplantation and whether the prevalence of genetic causes differed from ambulatory cardiomyopathy cases.

METHODS

We performed whole exome and genome sequencing of 122 explanted hearts from 101 adult and 21 pediatric patients with idiopathic cardiomyopathy from a single center. Data were analyzed for pathogenic/likely pathogenic variants in nuclear and mitochondrial genomes and assessed for nonhuman microbial sequences. The frequency of damaging genetic variants was compared among cardiomyopathy cohorts with different clinical severity.

RESULTS

Fifty-four samples (44.3%) had pathogenic/likely pathogenic cardiomyopathy gene variants. The frequency of pathogenic variants was similar in pediatric (42.9%) and adult (43.6%) samples, but the distribution of mutated genes differed (P=8.30×10-4). The prevalence of causal genetic variants was significantly higher in end-stage than in previously reported ambulatory adult dilated cardiomyopathy cases (P<0.001). Among remaining samples with unexplained causes, no damaging mitochondrial variants were identified, but 28 samples contained parvovirus genome sequences, including 2 samples with 6- to 9-fold higher levels than the overall mean levels in other samples.

CONCLUSIONS

Pathogenic variants and viral myocarditis were identified in 45.9% of patients with unexplained end-stage cardiomyopathy. Damaging gene variants are significantly more frequent among transplant compared with patients with ambulatory cardiomyopathy. Genetic analyses can help define cause of end-stage cardiomyopathy to guide management and risk stratification of patients and family members.

Left ventricular non-compaction cardiomyopathy associated with the PRKAG2 mutation

Left ventricular non-compaction cardiomyopathy (LVNC) is one of the most common inherited cardiovascular diseases. The genetic backgrounds of most LVNC patients are not fully understood. We collected clinical data, family histories, and blood samples and performed genetic analysis using next-generation sequencing (NGS) from a Chinese family of 15 subjects. Clinically LVNC affected subjects showed marked cardiac phenotype heterogeneity. We found that these subjects with LVNC carried a missense heterozygous genetic mutation c.905G>A (p.R302Q) in γ2 subunit of AMP-activated protein kinase (PRKAG2) gene through NGS. Individuals without this mutation showed no symptoms or cardiac structural abnormalities related to LVNC. One subject was the victim of sudden cardiac death. To sum up, PRKAG2 mutation c.905G>A (p.R302Q) caused familial LVNC. Our results described a potentially pathogenic mutation associated with LVNC, which may further extend the spectrum of LVNC phenotypes related to PRKAG2 gene mutations.

Detection of intracellular histological abnormalities using cardiac magnetic resonance T1 mapping in patients with Danon disease: a case series

Background

Danon disease is an X-linked dominant disorder with defects in the lysosome-associated membrane protein 2 (LAMP2) gene and is characterized histologically by intracellular autophagic vacuoles in skeletal and cardiac muscles. Cardiac magnetic resonance (CMR) T1 mapping potentially allows to differentiate intracellular and extracellular cardiac abnormalities with a combination of native T1 value and extracellular volume (ECV) fraction.

Case summary

We assessed CMR T1 mapping in two Danon disease patients (a 22-year-old man and his 48-year-old mother), who had a LAMP2 c.864G>A p. Val288Val mutation, and two blood relatives without Danon disease (his 47-year-old maternal aunt and 49-year-old father). The male patient underwent a left ventricular (LV) assist device implantation at 15 months after the image acquisition because he was inotrope dependent (INTERMACS profile 3) and had no noticeable psychological or musculoskeletal symptoms. His mother was in New York Heart Association Class II with mildly reduced LV ejection fraction (46%). The Danon group showed late gadolinium enhancement (LGE) in the anterior and posterolateral LV walls. In the interventricular wall, where evident LGE was not noted, the Danon group had high native T1 value, compared with the T1 value in the non-Danon group, and normal ECV fraction. Cardiac biopsy from the interventricular wall showed intracytoplasmic autophagic vacuoles, which are characteristics of Danon disease.

Discussion

This characteristic pattern of high native T1 and normal ECV fraction in the areas without LGE, which may reflect the existence of intracytoplasmic autophagic vacuoles, may support the differential diagnosis of Danon disease from other cardiomyopathies.

Cardiac Phenotype Characterization at MRI in Patients with Danon Disease: A Retrospective Multicenter Case Series

Danon disease (DD) is a rare X-chromosome-linked dominant lysosomal glycogen storage disease. Its features have seldom been reported by using cardiac MRI. This case series aimed to evaluate cardiac features of DD on the basis of MRI observations from five centers in China. From January 2010 to May 2019, 16 patients with DD (13 male patients [81%]; median age, 19 years; age range, 14-44 years) underwent MRI. The most frequent DD cardiomyopathy manifestation was symmetric hypertrophy cardiomyopathy (HCM) phenotype (nine of 16; 56%), followed by asymmetric HCM phenotype (six of 16; 38%) and dilated cardiomyopathy phenotype (one of 16; 6%). The characteristic late gadolinium enhancement features included midbasal septum sparing (14 of 16; 88%) and apex involvement (16 of 16; 100%) with a base-to-apex increasing tendency, free wall involvement (15 of 16; 94%), and extensive subendocardium involvement (14 of 16; 88%). Abnormal T2 signal (seven of 16; 44%) and resting perfusion defect (14 of 16; 88%) were not uncommon in patients with DD. Furthermore, the cardiac MRI features of DD cohort in this study were compared with those of DD in previous literature and with genetically confirmed sarcomeric HCM.

Clinical features and cardiovascular magnetic resonance characteristics in Danon disease

AIMS

To investigate the clinical spectrum, cardiovascular magnetic resonance imaging (cMRI) characteristics, including T1 and extracellular volume fraction, and outcomes of Danon disease to facilitate further understanding of the phenotype of patients with Danon disease.

MATERIALS AND METHODS

The study comprised six male patients 8-23 years old recruited to the study between 2014-2019. The clinical presentation, laboratory examinations, pathology/genetic analysis, electrocardiography (ECG), echocardiography, and cCMRI characteristics were summarised.

RESULTS

Five out of six patients suffered from hypertrophic cardiomyopathy (HCM) phenotype of Danon disease, while one patient had dilated cardiomyopathy (DCM) phenotype. Left ventricular (LV) and left atrial (LA) function were impaired at strain measurement. Diffuse and focal late gadolinium enhancement (LGE) were observed separately in the LV walls of three patients and right ventricular (RV) insertion points of the remaining three patients. Furthermore, values for the native T1 (mean 1313.3 ms) and extracellular volume fraction (ECV; mean 39.17%) of three patients were increased.

CONCLUSIONS

Both dilated and hypertrophic cardiomyopathy may be the phenotypes of Danon disease. Comprehensive cCMRI played a unique role in the diagnosis and grading severity and risk factors of Danon disease in vivo, especially by using robust quantitative strain analysis, T1 mapping, and further ECV calculation.