Fabry disease Schwann cells release p11 to induce sensory neuron hyperactivity

Patients with Fabry disease suffer from chronic debilitating pain and peripheral sensory neuropathy with minimal treatment options, but the cellular drivers of this pain are unknown. Here, we propose a mechanism we believe to be novel in which altered signaling between Schwann cells and sensory neurons underlies the peripheral sensory nerve dysfunction we observed in a genetic rat model of Fabry disease. Using in vivo and in vitro electrophysiological recordings, we demonstrated that Fabry rat sensory neurons exhibited pronounced hyperexcitability. Schwann cells probably contributed to this finding because application of mediators released from cultured Fabry Schwann cells induced spontaneous activity and hyperexcitability in naive sensory neurons. We examined putative algogenic mediators using proteomic analysis and found that Fabry Schwann cells released elevated levels of the protein p11 (S100A10), which induced sensory neuron hyperexcitability. Removal of p11 from Fabry Schwann cell media caused hyperpolarization of neuronal resting membrane potentials, indicating that p11 may contribute to the excessive neuronal excitability caused by Fabry Schwann cells. These findings demonstrate that sensory neurons from rats with Fabry disease exhibit hyperactivity caused in part by Schwann cell release of the protein p11.

Left atrial strain correlates with severity of cardiac involvement in Anderson-Fabry disease

OBJECTIVES

Cardiac involvement in Anderson-Fabry disease (AFD) results in myocardial lipid depositions. An early diagnosis can maximize therapeutic benefit. Thus, this study aims to investigate the potential of cardiac MRI (CMR) based parameters of left atrial (LA) function and strain to detect early stages of AFD.

METHODS

Patients (n = 58, age 40 (29-51) years, 31 female) with genetically proven AFD had undergone CMR including left ventricular (LV) volumetry, mass index (LVMi), T1, and late gadolinium enhancement, complemented by LA and LV strain measurements and atrial emptying fractions. Patients were stratified into three disease phases and compared to age and sex-matched healthy controls (HC, n = 58, age 41 [26-56] years, 31 female).

RESULTS

A total of 19 early-, 20 intermediate-, and 19 advanced-phase patients were included. LV and LA reservoir strain was significantly impaired in all AFD phases, including early disease (both p < 0.001). In contrast, LA volumetry, T1, and LVMi showed no significant differences between the early phase and HC (p > 0.05). In the intermediate phase, LVMi and T1 demonstrated significant differences. In advanced phase, all parameters except active emptying fractions differed significantly from HC. ROC curve analyses of early disease phases revealed superior diagnostic confidence for the LA reservoir strain (AUC 0.88, sensitivity 89%, specificity 75%) over the LV strain (AUC 0.82).

CONCLUSIONS

LA reservoir strain showed impairment in early AFD and significantly correlated with disease severity. The novel approach performed better in identifying early disease than the established approach using LVMi and T1. Further studies are needed to evaluate whether these results justify earlier initiation of therapy and help minimize cardiac complications.

KEY POINTS

• Parameters of left atrial function and deformation showed impairments in the early stages of Anderson-Fabry disease and correlated significantly with the severity of Anderson-Fabry disease. • Left atrial reservoir strain performed superior to ventricular strain in detecting early myocardial involvement in Anderson-Fabry disease and improved diagnostic accuracies of approaches already using ventricular strain. • Further studies are needed to evaluate whether earlier initiation of enzyme replacement therapy based on these results can help minimize cardiac complications from Anderson-Fabry disease.

An expert consensus on practical clinical recommendations and guidance for patients with classic Fabry disease

Fabry disease is an X-linked inherited lysosomal disorder that causes accumulation of glycosphingolipids in body fluids and tissues, leading to progressive organ damage and reduced life expectancy. It can affect both males and females and can be classified into classic or later-onset phenotypes. In classic Fabry disease, α-galactosidase A (α-Gal A) activity is absent or severely reduced and disease manifestations have an early onset that can affect multiple organs. In contrast, in later-onset Fabry disease, patients have residual α-Gal A activity and clinical features are primarily confined to the heart. Individualized therapeutic goals in Fabry disease are required due to varying phenotypes and patient characteristics, and the wide spectrum of disease severity. An international group of expert physicians convened to discuss and develop practical clinical recommendations for disease- and organ-specific therapeutic goals in Fabry disease, based on expert consensus and evidence identified through a structured literature review. Biomarkers reflecting involvement of various organs in adult patients with classic Fabry disease are discussed and consensus recommendations for disease- and organ-specific therapeutic goals are provided. These consensus recommendations should support the establishment of individualized approaches to the management of patients with classic Fabry disease by considering identification, diagnosis, and initiation of disease-specific therapies before significant organ involvement, as well as routine monitoring, to reduce morbidity, optimize patient care, and improve patient health-related quality of life.

Rare presentation of Fabry disease as 'burnt-out' hypertrophic cardiomyopathy

We herein report the case of a 53-year-old man who was historically diagnosed with hypertrophic cardiomyopathy (HCM) and was lost to follow-up, before presenting with end-stage heart failure. This was initially suspected as dilated cardiomyopathy and then 'burnt-out phase' of HCM but subsequently the underlying diagnosis was Fabry disease. Fabry disease is an uncommon lysosomal-storage disease due to reduced or absent activity of the alpha-galactosidase A enzyme. Cardiac involvement most frequently comprises left ventricular hypertrophy. Early treatment of the underlying condition with enzyme replacement therapy may prevent the progression to end-stage heart failure. Fabry disease should be considered in all patients presenting with a clinical phenotype of HCM and a historical diagnosis should be re-evaluated in light of new diagnostic tools. Untreated Fabry can progress to a 'burnt out' phase, whereby initial hypertrophy undergoes eccentric remodelling to a dilated, severely impaired left ventricle.

Restrictive cardiomyopathy in a patient with systemic sclerosis and Fabry disease: a case-based review

Systemic sclerosis (SSc) is a rare immune-mediated vasculopathy characterized by fibrosis of the skin and internal organs. Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations in the GLA gene producing α-galactosidase-A enzyme (α-Gal A) deficiency. Being a systemic disease, cardiac involvement in FD has a high mortality rate due to heart failure and arrhythmia. The coexistence of these two entities has not been reported previously. We describe the case of a female patient with limited SSc (lcSSc), a diagnosis based on the presence of sclerodactyly, Raynaud phenomenon, microvascular involvement, and positive anti-centromere antibodies. On follow-up, she developed chest pain, a second-degree A-V block, and restrictive cardiomyopathy (without cardiovascular risk factors). Although heart involvement is common in these two entities, the abnormal thickening of lateral and inferior wall, the infiltration pattern and the conduction system disorders presented herein are more characteristic in a heterozygous female with a cardiac variant of FD. The diagnosis of FD was confirmed with high globotriaosylsphingosine (Lyso-Gb3) levels and identification of GLA gene mutation. The patient was treated with enzymatic replacement (agalsidase alpha) following mild improvement in ventricular mass at 6th month, without clinical deterioration. The related literature on SSc associated with FD is also reviewed.

Diagnosis and treatment of the cardiovascular consequences of Fabry disease

Fabry disease (FD) has been a diagnostic challenge since it was first recognized in 1898, with patients traditionally suffering from considerable delay before a diagnosis is made. Cardiac involvement is the current leading cause of death in FD. A combination of improved enzyme assays, availability of genetic profiling, together with more organized clinical services for rare diseases, has led to a rapid growth in the prevalence of FD. The earlier and more frequent diagnosis of asymptomatic individuals before development of the phenotype has focussed attention on early detection of organ involvement and closer monitoring of disease progression. The high cost of enzyme replacement therapy at a time of constraint within many health economies, moreover, has challenged clinicians to target treatment effectively. This article provides an outline of FD for the general physician and summarizes the aetiology and pathology of FD, the cardiovascular consequences thereof, modalities used in diagnosis and then discusses current indications for treatment, including pharmacotherapy and device implantation.