Long-term outcome of enzyme-replacement therapy in advanced Fabry disease: evidence for disease progression towards serious complications

OBJECTIVE

The long-term effects of enzyme-replacement therapy (ERT) in Fabry disease are unknown. Thus, the aim of this study was to determine whether ERT in patients with advanced Fabry disease affects progression towards 'hard' clinical end-points in comparison with the natural course of the disease.

METHODS

A total of 40 patients with genetically proven Fabry disease (mean age 40 ± 9 years; n = 9 women) were treated prospectively with ERT for 6 years. In addition, 40 subjects from the Fabry Registry, matched for age, sex, chronic kidney disease stage and previous transient ischaemic attack (TIA), served as a comparison group. The main outcome was a composite of stroke, end-stage renal disease (ESRD) and death. Secondary outcomes included changes in myocardial left ventricular (LV) wall thickness and replacement fibrosis, change in glomerular filtration rate (GFR), new TIA and change in neuropathic pain.

RESULTS

During a median follow-up of 6.0 years (bottom and top quartiles: 5.1, 7.2), 15 events occurred in 13 patients (n = 7 deaths, n = 4 cases of ESRD and n = 4 strokes). Sudden death occurred (n = 6) only in patients with documented ventricular tachycardia and myocardial replacement fibrosis. The annual progression of myocardial LV fibrosis in the entire cohort was 0.6 ± 0.7%. As a result, posterior end-diastolic wall thinning was observed (baseline, 13.2 ± 2.0 mm; follow-up, 11.4 ± 2.1 mm; P < 0.01). GFR decreased by 2.3 ± 4.6 mL min(-1) per year. Three patients experienced a TIA. The major clinical symptom was neuropathic pain (n = 37), and this symptom improved in 25 patients. The event rate was not different between the ERT group and the untreated (natural history) group of the Fabry Registry.

CONCLUSION

Despite ERT, clinically meaningful events including sudden cardiac death continue to develop in patients with advanced Fabry disease.

Right ventricular involvement in patients with Fabry's disease and the effect of enzyme replacement therapy

PURPOSE

According to echocardiography reports, Fabry cardiomyopathy not only affects the left ventricle (LV) but also the right ventricle (RV). Until now no MRI studies about the effect of enzyme replacement therapy (ERT) on the RV are available. We evaluated the effect of ERT on the RV.

MATERIALS AND METHODS

In this prospective trial 14 patients with genetically proven Fabry's disease were examined using a 1.5 T MR scanner before ERT and after 13 ± 1 months of ERT. All patients underwent cardiac MR imaging and the RV/LV cardiac morphology and function were analyzed.

RESULTS

At baseline examination the values were as follows: RV mass 31 ± 6 g/m (2), end-diastolic volume (EDV) 88 ± 13 ml/m (2), end-systolic volume (ESV) 39 ± 9 ml/m (2), stroke volume (SV) 49 ± 7 ml/m (2) and ejection fraction (EF) 56 ± 5 %. The RV mass and EDV decreased significantly after 13 ± 1 months on ERT (mass 27 ± 7 g/m (2), p < 0.05, EDV 76 ± 24 ml/m (2), p < 0.05), with no significant change of ESV (33 ± 13 ml/m (2)), SV (43 ± 12 ml/m (2)) and EF (57 ± 7 %). The LV mass (102 ± 26 g/m (2) vs. 94 ± 27 g/m (2), p < 0.05), EDV (76 ± 13 ml/m (2) vs. 66 ± 22 ml/m (2), p < 0.05) and ESV (29 ± 9 ml/m (2) vs. 23 ± 9 ml/m (2), p < 0.05) decreased significantly while the EF (64 ± 7 % vs. 66 ± 5 %; p < 0.05) increased significantly.

CONCLUSION

Besides the known beneficial effect on the LV, ERT improves RV mass and EDV.

Nomen est omen. Fabry disease

A 47-year-old woman was referred with increasing dyspnoea and neuropathic pain. During echocardiography, she showed the typical signs for a Fabry cardiomyopathy: global left ventricular function was normal with an ejection fraction of 65%. She had a concentric left ventricular hypertrophy with very prominent papillary muscles. In addition, the magnetic resonance tomography showed regional late enhancement in the postero-lateral wall which is the typical location of fibrosis in Fabry patients. She suffered from a genetically proven Fabry disease, and interestingly her family name is Mrs Fabry. Thus summarized, Mrs Fabry with a confirmed Fabry disease presented with a typically Fabry cardiomyopathy.

Misleading terms in Anderson-Fabry disease

BACKGROUND

Signs and symptoms of classic Fabry disease manifest itself on the skin (angiokeratoma), the nervous system (acroparaesthesia), the heart (restrictive cardiomyopathy) and a variety of other organs.

MATERIALS AND METHODS

Diagnosis of Fabry disease was confirmed by genetic tests in a cohort of 100 patients and a standardized examination programme was performed in all patients. We were puzzled when applying well-established and textbook-anchored signs and symptoms to our patients.

RESULTS

Among the 47 male and 53 female patients (mean age 41 +/- 16 years) with genetically proven disease, the Fabry-type vascular skin lesions were without hyperkeratotic aspect and keratomas were virtually absent. The peripheral neuropathic pain found in all male patients was not compatible with the wording 'acro' and 'paraesthesia', suggesting a different pathophysiological mechanism. Upon echocardiographic examination, patients mainly revealed diastolic relaxation abnormalities of the heart and only one patient had a restrictive cardiac pattern.

CONCLUSIONS

Our findings suggest that some terms used to describe signs and symptoms of Fabry disease are historically derived and do not comply with state-of-the-art examination. We propose to replace the term 'angiokeratoma' with 'angioma', the term 'acroparaesthesia' with 'neuropathic pain' and the term 'restrictive cardiomyopathy' with 'cardiac hypertrophic storage disease'. As most of the physicians are not familiar with Fabry disease, terms used in the past might prevent the correct diagnosis of a potentially treatable disease.

Phänotypisierung durch „genetic field work”: Ist die Datenerhebung durch Fragebögen ausreichend?

BACKGROUND AND OBJECTIVE

Genetic studies of complex diseases such as diabetes mellitus (DM) require the recruitment of patients and acquisition of patient data in a time- and cost-effective manner. An effective method to do so may be genetic field work (GFW) that recruits the relatives of index cases, these relatives then replying to appropriate questionnaires. This study investigated the validity of GFW data compared with patient interviews by a physician who had examined those persons.

METHODS

122 relatives were identified through GFW among a cohort of 35 families with DM. Questionnaires with self-reported information on past medical history, cardiovascular risk factors and life style were obtained. In a second step these famiy members were interviewed and examined by a physician in an outpatient setting.

RESULTS

Comparison of the two data sets of the 122 individuals yielded clear differences which favored interviews by a physician. The number of persons declaring themselves as having DM was significantly lower by GFW than direct examination (18 vs. 27). Diabetic nephropathy was reported by four individuals by GFW, while examination resulted in the identification of 16 cases. Body weight was also clearly too low when self-reported, so that significantly lower values were recorded for BMI in the questionnaire. Hypertension was reported by 25 vs. 54 participants. The amount of cigarettes smoked was significant lower in the GFW than in physicians' examination. But the numbers recorded for myocardial infarction, peripheral vascular disease and stroke were not significantly different.

CONCLUSION

These data show that information obtained by GFW is less accurate than that collected in interview and examination by physicians. The latter are necessary to gain valid data for accurate phenotyping, while GFW is useful in the initial recruitment of relatives.

Fabry disease: baseline medical characteristics of a cohort of 1765 males and females in the Fabry Registry

The Fabry Registry is a global observational research platform established to define outcome data on the natural and treated course of this rare disorder. Participating physicians submit structured longitudinal data to a centralized, confidential database. This report describes the baseline demographic and clinical characteristics of the first 1765 patients (54% males (16% aged < 20 years) and 46% females (13% < 20 years)) enrolled in the Fabry Registry. The median ages at symptom onset and diagnosis were 9 and 23 years (males) and 13 and 32 years (females), respectively, indicating diagnostic delays in both sexes. Frequent presenting symptoms in males included neurological pain (62%), skin signs (31%), gastroenterological symptoms (19%), renal signs (unspecified) (17%), and ophthalmological signs (11%). First symptoms in females included neurological pain (41%), gastroenterological symptoms (13%), ophthalmological (12%), and skin signs (12%). For those patients reporting renal progression, the median age at occurrence was 38 years for both sexes, but onset of cerebrovascular and cardiovascular events was later in females (median 43 and 47 years, respectively) than in males (38 and 41 years, respectively). This paper demonstrates that in spite of the considerable burden of disease in both sexes that begins to manifest in childhood or adolescence, the recognition of the underlying diagnosis is delayed by 14 years in males and 19 years in females. The Fabry Registry provides data that can increase awareness of common symptoms in all age groups, as well as insight into treated and untreated disease course, leading to improved recognition and earlier treatment, and possibly to improved outcomes for affected individuals.

Clinical benefit of enzyme replacement therapy in Fabry disease

Enzyme replacement therapy (ERT) with recombinant human alpha-galactosidase A (r-halphaGalA) enhances microvascular globotriaosylceramide clearance and improves clinical symptoms in patients with Fabry disease. We evaluated whether these effects are translated into a long-term benefit of kidney and heart function. We did a single center, prospective, open label study in 26 patients with Fabry disease (one early death, follow-up in 25 patients). r-Alpha-GalA was administered in a dosage of 1 mg/kg body weight every second week. The effect of therapy on clinical end points (death, cardiac and cerebrovascular event, renal failure), cardiac and renal function monitored by Doppler echocardiography, 99Tc-GFR, and proteinuria was investigated. After a mean treatment time of 23 +/- 8 months, nine patients experienced 12 end points, including two deaths. All end points occurred in patients with impaired renal function (n = 16; GFR 71 +/- 17 ml/min/1.73 m2). Despite ERT, renal function deteriorated to 60 +/- 23 ml/min/1.73 m2 (P = 0.04) and left ventricular posterior wall thickness (PWT) did not change (14.0 +/- 2.1 vs 13.4 +/- 2.3 mm). In contrast, patients without impairment of renal function (n = 9) had a more favorable outcome (no clinical events; GFR 115 +/- 18 vs 102 +/- 14 ml/min/1.73 m2, NS; PWT 11.7 +/- 1 and 10.7+/-0.7 mm, P = 0.04). Proteinuria remained unchanged (1.34 +/- 0.94 vs 1.01 +/- 0.97 g/day, n = 10). Patients with impaired renal function have a less favorable outcome and may develop cardiovascular and renal end points despite ERT.

Morbus Fabry of the heart

Fabry Disease is an X-linked lysosomal storage disorder leading to the accumulation of glycosphingolipids, mainly globotriaosylceramides in all tissues and solid organs of the body. The disease was described by Johannes Fabry and William Anderson coevally in 1898. Beside the involvement of the central nervous system, peripheral nerves, kidneys, skin and endovascular endothelium, the heart plays a major role in the disease. Left ventricular hypertrophy is one hallmark initially presenting with preserved ventricular function. However, with progression of the disease patients die due to heart failure. Though angina is often reported, the incidence of epicardial coronary stenosis is not a dominant feature, if at all small vessel disease can occur. In respect of arrhythmias a broad spectrum can be seen including shortened or prolonged PR-intervals, AV blocks of different degrees and sometimes malignant ventricular arrhythmias. In the past, women were considered to be carriers of the disease but hardly to develop clinical symptoms. In recent years there is evidence that female carriers may more often be affected with severe symptoms. In addition, a group of Fabry patients displaying mainly cardiac involvement were described as having a cardiac variant of the disease. This implied the hypothesis that some of those patients with unexplained myocardial hypertrophy do suffer from Fabry disease. Since 2002 enzyme replacement therapy is available and there is first evidence for its efficacy to reduce hypertrophy and increase myocardial function. If this is associated with a prognostic improvement has to be determined in future studies.