Fabry disease among hypertrophic cardiomyopathy of genetic origin

Primary hypertrophic cardiomyopathy is a relatively frequent disease (1/500) which results from a mutation in a gene encoding a sarcomeric protein. In a series of 184 cases, nearly half (46 %) were secondary to a mutation in one of the 4 following genes : MYBPC3, MYH7, TNNI3, TNNT2. In Fabry disease, an exclusive or nearly exclusive cardiac expression is possible and referred to as "cardiac variant". The hypertrophic cardiomyopathy of Fabry disease is usually unspecific. Two series reported a prevalence of Fabry disease of about 6% among male cases. An Italian series of 34 female cases with hypertrophic cardiomyopathy demonstrated that it was feasible to diagnose Fabry disease in females by screening for specific lesions in myocardial biopsies. We detected a patient who initially presented with a common hypertrophic cardiomyopathy except that his ECG showed depression of ST segment and inversion of T wave in leads D1, VL and in precordial leads. The family history revealed several affected relatives and female carriers. In conclusion, an isolated common hypertrophic cardiomyopathy may be secondary to Fabry disease. Male patients should be screened systemically for enzyme defect except in cases of father-to-son transmission. In females, an affected male relative should be searched for screening or the GLA gene should be sequenced. It is important to think about a putative Fabry disease in cases with hypertrophic cardiomyopathy not associated with any obvious cause.     

Awareness of Fabry disease in cardiology: A gap to be filled

Introduction

In adults, unexplained left ventricular hypertrophy is usually due to sarcomeric hypertrophic cardiomyopathy (HCM). Fabry disease (FD) is rare but may mimic sarcomeric HCM, and has an adverse prognosis in the absence of specific treatment. We aimed to assess cardiologists’ awareness of FD based on data from the Portuguese Registry of Hypertrophic Cardiomyopathy.

Epidemiologic and clinical characteristics of cardiomyopathies in Japan: results from nationwide surveys.

Nationwide clinico-epidemiological surveys of cardiomyopathies in Japan were carried out. Disorders surveyed included idiopathic dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy (RCM), arrhythmogenic right ventricular dysplasia (ARVD), mitochondrial disease, Fabry's disease of the heart and prolonged Q-T interval syndrome. The total number of patients was estimated at 17,700 for DCM, 21,900 for HCM, 300 for RCM, 520 for ARVD, 640 for mitochondrial disease, 150 for Fabry's disease of the heart, and 1,000 for prolonged Q-T interval syndrome. The prevalence of both DCM and HCM was higher in men than women: the male-to-female ratios were 2.6 and 2.3 for DCM and HCM, respectively. Detailed data on patients with DCM or HCM were collected by a follow-up survey. In 1 year more patients with DCM (5.6%) died than with HCM (2.8%): congestive heart failure (CHF) and arrhythmias were the leading causes of death for DCM and HCM, respectively. Angiotensin converting enzyme inhibitors (64.6%) and beta-adrenergic blockers (40.9%) are commonly used to treat the CHF complicating DCM and may be associated with the clinical improvement in a significant number of DCM patients. Thus, the nationwide surveys of Japanese patients have yielded important current epidemiological and clinical information on the characteristics of cardiomyopathies in Japan.     

Prevalence of Fabry disease in a predominantly hypertensive population with left ventricular hypertrophy

Background

Patients with Fabry disease (FD) develop progressive left ventricular hypertrophy (LVH). In screening studies in patients with LVH, the prevalence of FD ranges from 0 to 12%. This variability is attributable to different factors like diverging inclusion and exclusion criteria, the evaluation of selected populations and suboptimal screening methods.In this study, we aimed to determine the prevalence of FD in an unselected population of everyday clinical practice presenting LVH, defined as a maximal end-diastolic septal or posterior wall thickness ≥ 13 mm, without exclusion of patients with arterial hypertension or valvular pathology, and using optimal screening methods.

Methods

In adult males, a two-tier approach was used; α-Galactosidase A (aGAL A) activity was measured using a dried bloodspot test (DBS) and diagnosis was confirmed by mutation analysis of the GLA gene. In females, mutation analysis was the primary screening tool.

Results

362 men and 178 women were screened. Six patients were diagnosed with a genetic sequence alteration of the GLA gene. One man had a novel mutation, GLA p.Ala5Glu (c.44C > A), presenting as classical FD. Another man and three women had the previously described GLA p.Ala143Thr (c.427G > A) mutation, which generally presents as an attenuated phenotype. One woman had a novel sequence alteration c.639 + 6A > C, which appeared to be a polymorphism. All true Fabry patients had arterial hypertension (AHT), and one had hypertrophic obstructive cardiomyopathy (HOCM).

Conclusions

In a group of unselected patients with LVH, we found a prevalence of Fabry disease of 0.9%. AHT or type of hypertrophy should not be an exclusion criterion for screening for FD.     

Fabry's disease cardiomyopathy: echocardiographic detection of endomyocardial glycosphingolipid compartmentalization.

OBJECTIVES: We sought to identify echocardiographic hallmarks of Fabry's disease cardiomyopathy (FC). BACKGROUND: The recognition of FC from other forms of left ventricular hypertrophy (LVH) by noninvasive imaging techniques is not yet available, and diagnosis, mostly in the absence of systemic manifestations, still relies on genetic and invasive studies. METHODS: Forty consecutive patients (mean age 39 +/- 15 years, 22 men and 18 women) with an established diagnosis of Fabry's disease were submitted to echocardiographic evaluation. Control population consisted of 40 consecutive patients with hypertrophic cardiomyopathy (HCM), 40 hypertensive patients with echocardiographic evidence of LVH, and 40 age- and gender-matched healthy subjects with no LVH. All HCM patients and FC with LVH and/or cardiac symptoms underwent cardiac catheterization with left ventricular endomyocardial biopsy. RESULTS: Echocardiography showed in 83% of FC patients (95% of FC patients with LVH) a binary appearance of endocardial border absent in all HCM, hypertensive, and healthy subjects. The sensitivity and specificity of this echocardiographic feature in detecting Fabry patients in study population were 94% and 100%, respectively. Comparison of echocardiographic with histologic and ultrastructural findings showed the binary appearance to reflect an endomyocardial glycosphingolipids compartmentalization, consisting of thickened glycolipid-rich endocardium, free glycosphingolipid subendocardial storage, and an inner severely affected myocardial layer with a clear subendocardial-midwall layer gradient of disease severity. CONCLUSIONS: Echocardiographic binary appearance of left ventricular endocardial border, reflecting endomyocardial glycosphingolipids compartmentalization, represents a sensitive and specific diagnostic hallmark of Fabry's disease cardiomyopathy.     

肥厚型心肌病样临床表现的Fabry病家系研究

目的对一个临床表现酷似肥厚型心肌病的Fabry病家系进行α-半乳糖苷酶（α-GalA）基因测序并发现其突变形式。方法该家系成员共15例,经过询问病史、体格检查、心电图及超声心动图检查,抽取外周静脉血标本,提取白细胞基因组DNA,PCR分段扩增α-GalA基因的7个外显子序列,产物纯化后直接测序,分析筛查基因的突变位点。结果家系中有9例发生α-GalA基因新的错义突变,突变位点位于α-GalA基因第5外显子的第32号密码子,均由TGG变为TGA,TGA为终止密码子,故可引起TGG正常编码的色氨酸残基编码中断。其中6例女性为带有突变基因的杂合子,3例男性为带有突变基因的半合子。9例患者中6例患有心肌肥厚。家系中正常人无此类突变。结论对心肌肥厚患者应与Fabry病进行鉴别诊断。α-GalA基因突变检测可用于Fabry病患者及其亲属,以明确诊断和进行病因学治疗。     

Uncertain diagnosis of Fabry disease: Consensus recommendation on diagnosis in adults with left ventricular hypertrophy and genetic variants of unknown significance

Background

Screening in subjects with left ventricular hypertrophy (LVH) reveals a high prevalence of Fabry disease (FD). Often, a diagnosis is uncertain because characteristic clinical features are absent and genetic variants of unknown significance (GVUS) in the α-galactosidase A (GLA) gene are identified. This carries a risk of misdiagnosis, inappropriate counselling and extremely expensive treatment. We developed a diagnostic algorithm for adults with LVH (maximal wall thickness (MWT) of > 12 mm), GLA GVUS and an uncertain diagnosis of FD.

Methods

A Delphi method was used to reach a consensus between FD experts. We performed a systematic review selecting criteria on electrocardiogram, MRI and echocardiography to confirm or exclude FD. Criteria for a definite or uncertain diagnosis and a gold standard were defined.

Results

A definite diagnosis of FD was defined as follows: a GLA mutation with ≤ 5% GLA activity (leucocytes, mean of reference value, males only) with ≥ 1 characteristic FD symptom or sign (neuropathic pain, cornea verticillata, angiokeratoma) or increased plasma (lyso)Gb3 (classical male range) or family members with definite FD. Subjects with LVH failing these criteria have a GVUS and an uncertain diagnosis. The gold standard was defined as characteristic storage in an endomyocardial biopsy on electron microscopy. Abnormally low voltages on ECG and severe LVH (MWT > 15 mm) < 20 years exclude FD. Other criteria were rejected due to insufficient evidence.

Conclusions

In adults with unexplained LVH and a GLA GVUS, severe LVH at young age and low voltages on ECG exclude FD. If absent, an endomyocardial biopsy with electron microscopy should be performed.     

A novel missense mutation in the myosin binding protein-C gene is responsible for hypertrophic cardiomyopathy with left ventricular dysfunction and dilation in elderly patients

OBJECTIVES: We studied the clinical features of hypertrophic cardiomyopathy (HCM) caused by a novel mutation in the myosin binding protein-C (MyBP-C) gene in patients and family members of Japanese descent. BACKGROUND: Previous reports have demonstrated that the clinical features of HCM associated with mutations in the MyBP-C gene include late onset and a favorable clinical course. Recently, some mutations in genes encoding sarcomeric proteins have been reported to be a cause of dilated cardiomyopathy (DCM), as well as HCM. However, mutations of the MyBP-C gene have not been reported as a cause of DCM up to now. METHODS: We analyzed MyBP-C gene mutations in 250 unrelated probands with HCM and in 90 with DCM. We used electrocardiography (ECG) and echocardiography to determine clinical phenotypes. RESULTS: We identified 17 individuals in 8 families (7 HCM, 1 DCM) with an Arg820Gln mutation in the MyBP-C gene. Overall, 2 (40%) of 5 carriers age >70 years displayed "burnt-out" phase HCM, and one of them had been diagnosed as having DCM before genetic identification. The disease penetrance in subjects age >50 years was 70% by echocardiography and 100% by ECG, and that in those age <50 years was 40% and 50%, respectively. CONCLUSIONS: Elderly patients with Arg820Gln mutation may show "burnt-out" phase HCM, and patients with this mutation may be included among those diagnosed as having DCM. Screening of patients with DCM, as well as HCM, for this mutation is of significant importance because patients with this mutation may be diagnosed clinically as having DCM.     

Comprehensive analysis of the beta-myosin heavy chain gene in 389 unrelated patients with hypertrophic cardiomyopathy

OBJECTIVES: We sought to determine the prevalence and phenotype of beta-myosin heavy chain gene MYH7 mutations in a large cohort of unrelated patients with hypertrophic cardiomyopathy (HCM). BACKGROUND: Hypertrophic cardiomyopathy is a heterogeneous cardiac disease. MYH7 mutations are one of the most common genetic causes of HCM and have been associated with severe hypertrophy, young age of diagnosis, and high risk of sudden cardiac death. However, these clinical findings from large, family studies have not been confirmed in a large unrelated cohort. METHODS: Deoxyribonucleic (DNA) samples obtained from 389 HCM outpatients seen at this tertiary referral center were analyzed for mutations, using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing for all 38 protein-coding exons of MYH7. Clinical data were extracted from patient records blinded to patient genotype. RESULTS: Fifty-eight patients (15%) harbored 40 different mutations in MYH7. Compared with HCM patients without MYH7 mutations, HCM patients with MYH7 were younger at diagnosis (32.9 vs. 42.7 years, p = 0.0002), had more hypertrophy (left ventricular wall thickness of 24.2 vs. 21.1 mm, p = 0.0009), and more frequently underwent myectomy (60% vs. 38%, p = 0.002). The HCM patients with MYH7 mutations more often had a family history of HCM (43% vs. 29%, p = 0.006), but there was no difference in family history of sudden death (16% vs. 14%, p = NS). CONCLUSIONS: In this setting, HCM patients with MYH7 were diagnosed at a younger age and had more hypertrophy, but they had no greater frequency of sudden death among first-degree relatives. Although these associations may prove useful for targeted gene screening, caution should be exercised in terms of using pathogenic status in risk stratification.     

Simple criteria for differentiation of Fabry disease from amyloid heart disease and other causes of left ventricular hypertrophy

AIMS: Fabry disease may be difficult to differentiate from other causes of left ventricular hypertrophy such as other myocardial storage diseases (including amyloidosis), hypertrophic cardiomyopathy (HCM), or hypertensive heart disease (HHD). We sought to determine simple criteria to best differentiate the above mentioned cardiac diseases. METHODS AND RESULTS: All patients in a six-year time period with left ventricular hypertrophy due to Fabry disease (13 patients), biopsy proven cardiac amyloidosis (16 patients), non-obstructive HCM (17 patients), and 22 randomly selected patients with advanced HHD were compared. Retrospective analysis of clinical characteristics, findings of electrocardiogram (ECG) and echocardiography by blind review was performed. RESULTS: No single clinical characteristic or findings of ECG or echocardiography could reliably differentiate between the various diseases. Increased echogenicity/granular sparkling, valvular abnormalities, abnormal renal function, and diastolic function were not helpful discriminators. In a univariate analysis, four criteria (acroparesthesia, anhydrosis, absence of hypertension and presence of Sokolow criteria for left ventricular hypertrophy in the ECG) were significant for Fabry disease. By logistic regression analysis, the following most suitable discriminative parameters were identified: hypertension in HHD (specificity 82%), orthostasis and/or pericardial effusion for amyloidosis (specificity 93%), papillary muscle anomaly in non-obstructive HCM (specificity 92%), and Fabry disease if neither hypertension orthostatis, pericardial effusion nor a papillary muscle anomaly was present (specificity 87%). CONCLUSION: A combination of symptoms, echocardiographic findings and ECG in unexplained left ventricular hypertrophy may help to differentiate amyloidosis, non-obstructive HCM and hypertensive heart disease from Fabry disease. The results of this preliminary study will have to be confirmed in a prospective study.     

Screening for Fabry Disease in Left Ventricular Hypertrophy: Documentation of a Novel Mutation

Background

Fabry disease is a lysosomal storage disease caused by enzyme α-galactosidase A deficiency as a result of mutations in the GLA gene. Cardiac involvement is characterized by progressive left ventricular hypertrophy.

Objective

To estimate the prevalence of Fabry disease in a population with left ventricular hypertrophy.

Methods

The patients were assessed for the presence of left ventricular hypertrophy defined as a left ventricular mass index ≥ 96 g/m² for women or ≥ 116 g/m² for men. Severe aortic stenosis and arterial hypertension with mild left ventricular hypertrophy were exclusion criteria. All patients included were assessed for enzyme α-galactosidase A activity using dry spot testing. Genetic study was performed whenever the enzyme activity was decreased.

Results

A total of 47 patients with a mean left ventricular mass index of 141.1 g/m² (± 28.5; 99.2 to 228.5 g/m²] were included. Most of the patients were females (51.1%). Nine (19.1%) showed decreased α-galactosidase A activity, but only one positive genetic test − [GLA] c.785G>T; p.W262L (exon 5), a mutation not previously described in the literature. This clinical investigation was able to establish the association between the mutation and the clinical presentation.

Conclusion

In a population of patients with left ventricular hypertrophy, we documented a Fabry disease prevalence of 2.1%. This novel case was defined in the sequence of a mutation of unknown meaning in the GLA gene with further pathogenicity study. Thus, this study permitted the definition of a novel causal mutation for Fabry disease - [GLA] c.785G>T; p.W262L (exon 5).     

Phenotype and genotype characterization and twin association in patients with Anderson-Fabry cardiomyopathy

Anderson-Fabry disease (FD), an X-linked recessive lysosomal storage disorder caused by a deficiency of α-galactosidase A (α-Gal A) activity, is associated with cardiac manifestations including arrhythmias, valvular abnormalities, and cardiomyopathy. Early initiation of enzyme replacement therapy (ERT) may have the potential to delay the underlying clinical outcomes in patients with FD. Clinical electrocardiogram (ECG) and echocardiography were used to characterize the cardiomyopathy. Diagnosis of FD was performed by measuring the α-Gal A activity in plasma and mutation analysis by direct sequencing using capillary electrophoresis. We identified four adult hemizygous male patients with cardiomyopathy and other symptoms related to FD; two of them were monozygotic twins. In all cases, ECG and echocardiography showed severe left ventricular (LV) hypertrophy. Some years later, all patients showed typical symptoms of FD, including angiokeratomas and neurological, renal, gastrointestinal, and ocular involvement. A deficiency of α-Gal A activity and point mutations in exon 5 of the GLA gene were detected in all patients. ERT (agalsidase-alfa) was administered every other week as a 0.2 mg/kg intravenous infusion over 40 min. In conclusion, these findings highlight the importance of screening middle-aged patients with LV hypertrophy for the early detection of FD, particularly in direct-line relatives such as twins.     

Prevalence of Fabry disease in male patients with unexplained left ventricular hypertrophy in primary cardiology practice: prospective Fabry cardiomyopathy screening study (FACSS)

Background

A number of studies have already investigated the prevalence of Fabry disease (FD) in adult patients with unexplained left ventricular hypertrophy (LVH) with rates varying from 0 % up to 12 % reflecting referral and gender bias as well as differences in diagnostic methodology. We aimed to perform a prospective screening study evaluating the prevalence of FD in male patients older than 30 years with strictly defined unexplained LVH followed by general cardiologists.

Methods

A predefined number of 100 men with unexplained LVH, defined as maximal wall thickness ≥ 13 mm, were identified during an echocardiographic examination in primary cardiology practice and screened by assessing α-galactosidase A activity in dried blood spots (DBS) or in plasma.

Results

Four men (52?±?4 years, maximal LV wall thickness 18?±?3 mm) were diagnosed with FD confirmed by enzyme analysis in leukocytes as well as by genetic analysis. Mild extracardiac manifestations of FD were present in two of them.

Conclusions

The prevalence of FD in our cohort of male patients followed in primary cardiology practice with strictly defined otherwise unexplained LVH was 4 %. We recommend systematic screening for FD in all men older than 30 years with LVH of unknown etiology even in the absence of obvious extracardiac manifestations of FD.     

Phenotype,disease severity and pain are major determinants of quality of life in Fabry disease: results from a large multicenter cohort study

Quality of life (QoL) is decreased in patients with Fabry disease (FD). To improve QoL, it is important to understand the influence of FD related characteristics, symptoms, and complications. In this retrospective cohort study we explored the effect of pain (measured by the Brief Pain Inventory), phenotype, treatment, and FD-related complications on QoL. QoL data of Fabry patients as assessed by the EuroQol five dimension questionnaire (EQ-5D) from two international centers of excellence were collected. The aim of this study was to evaluate the effect of sex, phenotype, age, different states of disease severity, pain, and ERT on EQ-5D utilities. For 286 adult FD patients (mean age 42.5 years, 40% men, 60% classical phenotype) 2240 EQ-5Ds were available. QoL is decreased in men as well as women with FD, especially in older men with a classical phenotype. At age 50, utility was lower in men with classical FD compared to those with non-classical disease (β = ?0.12, 95% CI: -0.23 – 0.01, p = 0.037) with further difference in the years thereafter. Cardiovascular complications, stroke or transient ischemic attacks, multiple FD-related complications and pain were also associated with decreased utilities. Overall, no change in utility was seen in patients on ERT over a mean follow-up of 6.1 years. FD leads to a decreased QoL compared to the general population. Disease complications and pain both negatively influence QoL. Adequate assessment and treatment of pain as well as improved strategies to prevent disease complications are needed to improve QoL in the FD population.     

Prevalence and association of ventricular tachycardia and complex ventricular arrhythmias with new coronary events in older men and women with and without cardiovascular disease

BACKGROUND: We report the prevalence of ventricular tachycardia (VT) and of complex ventricular arrhythmias (VA) and their association with new coronary events in older men and women. METHODS: The prevalence of VT and of complex VA detected by 24-hour ambulatory electrocardiograms and the incidence of new coronary events in older persons with coronary artery disease (CAD), with hypertension, valvular disease, or cardiomyopathy without CAD, and with no cardiovascular disease was investigated in 915 men (mean age 80 +/- 8 years) and in 1,874 women (mean age 81 +/- 8 years) in a long-term health care facility. Follow-up was 45 +/- 30 months in men and 47 +/- 30 months in women. RESULTS: The prevalence of VT was 16% in men and 15% in women with CAD, 9% in men and 8% in women with hypertension, valvular disease, or cardiomyopathy without CAD, and 3% in men and 2% in women with no cardiovascular disease. The prevalence of complex VA was 69% in men and 68% in women with CAD, 54% in men and 55% in women with hypertension, valvular disease, or cardiomyopathy without CAD, and 31% in men and 30% in women with no cardiovascular disease. In men and in women with CAD or with hypertension, valvular disease, or cardiomyopathy, VT and complex VA increased the incidence of new coronary events (p <.0001). Within each of the groups of patients, the incidences of new coronary events in men and in women with and without VT or complex VA were similar. CONCLUSIONS: The prevalence of VT and of complex VA were similar in older men and women. VT and complex VA were associated with a higher incidence of new coronary events in men and women with CAD or with hypertension, valvular disease, or cardiomyopathy without CAD, but not in men and women with no cardiovascular disease.     

D313Y variant in two related end-stage renal disease patients – Pathogenic or not yet?

Fabry disease is a multisystem lysosomal storage disorder caused by mutations in the GLA gene that result in a deficient or absent activity of alpha-galactosidase A. There is a wide spectrum of GLA gene variants, some of which are described as non-pathogenic. The clinical importance of the D313Y variant is still under debate, although in recent years it has been considered as a variant of unknown significance or a benign variant. Despite this prevailing notion, there are multiple case reports of patients with D313Y variant that presented signs and symptoms consistent with FD without any other etiological explanation. In this article, we present two family members with an important renal phenotype and other typical manifestations of FD (white matter lesions and left ventricular hypertrophy) that only had the D313Y variant. These cases suggest that this variant of unknown significance may contribute to the development of common features of FD and should not be undervalued.     

Pediatric cardiomyopathy: importance of genetic and metabolic evaluation

BackgroundCardiomyopathy is a heterogeneous disease with a strong genetic component. A research-based pediatric cardiomyopathy registry identified familial, syndromic, or metabolic causes in 30% of children. However, these results predated clinical genetic testing.Methods and ResultsWe determined the prevalence of familial, syndromic, or metabolic causes in 83 consecutive unrelated patients referred for genetic evaluation of cardiomyopathy from 2006 to 2009. Seventy-six percent of probands (n = 63) were categorized as familial, syndromic, or metabolic. Forty-three percent (n = 18) of hypertrophic cardiomyopathy (HCM) patients had mutations in sarcomeric genes, with MYH7 and MYBPC3 mutations predominating. Syndromic (17%; n = 7) and metabolic (26%; n = 11) causes were frequently identified in HCM patients. The metabolic subgroup was differentiated by decreased endocardial shortening fraction on echocardiography. Dilated cardiomyopathy (DCM) patients had similar rates of syndromic (20%; n = 5) and metabolic (16%; n = 4) causes, but fewer familial cases (24%; n = 6) compared with HCM patients.ConclusionsThe cause of cardiomyopathy is identifiable in a majority of affected children. An underlying metabolic or syndromic cause is identified in >35% of children with HCM or DCM. Identification of etiology is important for management, family-based risk assessment, and screening.     

Fabry disease: percutaneous transluminal septal myocardial ablation markedly improved symptomatic left ventricular hypertrophy and outflow tract obstruction in a classically affected male

Fabry disease (alpha-galactosidase A deficiency) is an X-linked recessive lysosomal storage disease in which left ventricular hypertrophy (LVH) is common, and if severe, may mimic hypertrophic obstructive cardiomyopathy. Alcohol-induced percutaneous transluminal septal myocardial ablation (PTSMA) has been used as a safe and effective method to alleviate LVH obstruction in patients with hypertrophic obstructive cardiomyopathy (HCM). We describe a case of a classically affected Fabry 53-year-old male with symptomatic HCM (NYHA class III with exertional angina) who was treated with PTSMA. The procedure safely and effectively alleviated symptomatic left ventricular outflow tract obstruction at long-term follow-up, and the patient's NYHA classification was reduced to NYHA class I to II.     

Myosin binding protein C mutations and compound heterozygosity in hypertrophic cardiomyopathy

OBJECTIVES: We sought to determine the frequency and phenotype of mutations in myosin binding protein C (MYBPC3) in a large outpatient cohort of patients with hypertrophic cardiomyopathy (HCM) seen at our tertiary referral center. BACKGROUND: Mutations in MYBPC3 are one of the most frequent genetic causes of HCM and have been associated with variable onset of disease and prognosis. However, the frequency of mutations and associated clinical presentation have not been established in a large, unrelated cohort of patients. METHODS: Using deoxyribonucleic acid from 389 unrelated patients with HCM, each protein coding exon of MYBPC3 was analyzed for mutations by polymerase chain reaction, denaturing high-performance liquid chromatography, and direct deoxyribonucleic acid sequencing. Clinical data were extracted from patient records blinded to patient genotype. RESULTS: Of 389 patients with HCM, 71 (18%) had mutations in MYBPC3. In all, 46 mutations were identified, 33 of which were novel (72%). Patients with MYBPC3 mutations did not differ significantly from patients with thick filament-HCM, thin filament-HCM, or genotype-negative HCM with respect to age at diagnosis, degree of hypertrophy, incidence of myectomy, or family history of HCM or sudden death. Patients with multiple mutations (n = 10, 2.6%) had the most severe disease presentation. CONCLUSIONS: This study defines the frequency and associated phenotype for MYBPC3 and/or multiple mutations in HCM in the largest cohort to date. In this cohort, unrelated patients with MYBPC3-HCM virtually mimicked the phenotype of those with mutations in the beta-myosin heavy chain. Patients with multiple mutations had the most severe phenotype.     

Adenosine monophosphate-activated protein kinase disease mimicks hypertrophic cardiomyopathy and Wolff-Parkinson-White syndrome: natural history

OBJECTIVES: The aim of this study was to investigate the clinical expression of adenosine monophosphate-activated protein kinase (AMPK) gene mutations (PRKAG2) in adenosine monophosphate (AMP) kinase disease based on 12 years follow-up of known mutation carriers and to define the prevalence of PRKAG2 mutations in hypertrophic cardiomyopathy (HCM). BACKGROUND: Adenosine monophosphate-activated protein kinase gene mutations cause HCM with Wolff-Parkinson-White syndrome and conduction disease. METHODS: Clinical evaluation of 44 patients with known AMP kinase disease was analyzed. Mutation analysis of PRKAG2 was performed by fluorescent single-strand confirmation polymorphism analysis and direct sequencing of abnormal conformers in 200 patients with HCM. RESULTS: Only one additional mutation was identified. The mean age at clinical diagnosis in the 45 gene carriers was 24 years (median 20 years, range 9 to 55 years). Symptoms of palpitation, dypspnea, chest pain, or syncope were present in 31 (69%) gene carriers; 7 (15%) complained of myalgia and had clinical evidence of proximal myopathy. Skeletal muscle biopsy showed excess mitochondria and ragged red fibers with minimal glycogen accumulation. Disease penetrance defined by typical electrocardiogram abnormalities was 100% by age 18 years. Thirty-two of 41 adults (78%) had left ventricular hypertrophy (LVH) on echocardiography, and progressive LVH was documented during follow-up. Survival was 91% at a mean follow-up of 12.2 years. Progressive conduction disease required pacemaker implantation in 17 of 45 (38%) at a mean age of 38 years. CONCLUSIONS: The AMP kinase disease is uncommon in HCM and is characterized by progressive conduction disease and cardiac hypertrophy and includes extracardiac manifestations such as a skeletal myopathy, consistent with a systemic metabolic storage disease. Defects in adenosine triphosphate utilization or in specific cellular substrates, rather than mere passive deposition of amylopectin, may account for these clinical features.