The Effect of Fabry Disease Therapy on Bone Mineral Density.

Fabry disease (FD) is an X-linked lysosomal storage disorder, characterised by the cellular accumulation of globotriaosylceramide due to impaired alpha-galactosidase A enzyme activity. FD may manifest with multisystem pathology, including reduced bone mineral density (BMD). Registry data suggest that the introduction of Fabry-specific therapies (enzyme replacement therapy or chaperone therapy) has led to significant improvements in overall patient outcomes; however, there are limited data on the impact on bone density. The aim of this study was to describe the effect of Fabry-specific therapies on longitudinal changes in bone mineral density (BMD) in FD. We performed a retrospective observational study analysing bone densitometry (DXA) in patients with genetically confirmed FD. Patients were grouped based on the use of Fabry-specific therapies. The between-group longitudinal change in BMD Z-score was analysed using linear mixed effects models. A total of 88 FD patients were analysed (50 untreated; 38 treated). The mean age at first DXA was 38.5 years in the untreated group (84% female) and 43.7 years in the treated group (34% female). There was no significant longitudinal between-group difference in the BMD Z-score at the lumbar spine. However, the Z-score per year at the total hip (ß = -0.105, p < 0.001) and femoral neck (ß = -0.081, p = 0.001) was significantly lower over time in the treated than the untreated group. This may reflect those receiving therapy having a more severe underlying disease. Nevertheless, this suggests that Fabry-specific therapies do not reverse all disease mechanisms and that the additional management of BMD may be required in this patient population.

GLA-modified RNA treatment lowers GB3 levels in iPSC-derived cardiomyocytes from Fabry-affected individuals.

Recent studies in non-human model systems have shown therapeutic potential of nucleoside-modified messenger RNA (modRNA) treatments for lysosomal storage diseases. Here, we assessed the efficacy of a modRNA treatment to restore the expression of the galactosidase alpha (GLA), which codes for α-Galactosidase A (α-GAL) enzyme, in a human cardiac model generated from induced pluripotent stem cells (iPSCs) derived from two individuals with Fabry disease. Consistent with the clinical phenotype, cardiomyocytes from iPSCs derived from Fabry-affected individuals showed accumulation of the glycosphingolipid Globotriaosylceramide (GB3), which is an α-galactosidase substrate. Furthermore, the Fabry cardiomyocytes displayed significant upregulation of lysosomal-associated proteins. Upon GLA modRNA treatment, a subset of lysosomal proteins were partially restored to wild-type levels, implying the rescue of the molecular phenotype associated with the Fabry genotype. Importantly, a significant reduction of GB3 levels was observed in GLA modRNA-treated cardiomyocytes, demonstrating that α-GAL enzymatic activity was restored. Together, our results validate the utility of iPSC-derived cardiomyocytes from affected individuals as a model to study disease processes in Fabry disease and the therapeutic potential of GLA modRNA treatment to reduce GB3 accumulation in the heart.

Clinical impact of genomic testing in patients with suspected monogenic kidney disease.

PURPOSE: To determine the diagnostic yield and clinical impact of exome sequencing (ES) in patients with suspected monogenic kidney disease. METHODS: We performed clinically accredited singleton ES in a prospectively ascertained cohort of 204 patients assessed in multidisciplinary renal genetics clinics at four tertiary hospitals in Melbourne, Australia. RESULTS: ES identified a molecular diagnosis in 80 (39%) patients, encompassing 35 distinct genetic disorders. Younger age at presentation was independently associated with an ES diagnosis (p < 0.001). Of those diagnosed, 31/80 (39%) had a change in their clinical diagnosis. ES diagnosis was considered to have contributed to management in 47/80 (59%), including negating the need for diagnostic renal biopsy in 10/80 (13%), changing surveillance in 35/80 (44%), and changing the treatment plan in 16/80 (20%). In cases with no change to management in the proband, the ES result had implications for the management of family members in 26/33 (79%). Cascade testing was subsequently offered to 40/80 families (50%). CONCLUSION: In this pragmatic pediatric and adult cohort with suspected monogenic kidney disease, ES had high diagnostic and clinical utility. Our findings, including predictors of positive diagnosis, can be used to guide clinical practice and health service design.

Elevated Lyso-Gb3 Suggests the R118C GLA Mutation Is a Pathological Fabry Variant.

BACKGROUND: Fabry disease (FD), an X-linked lysosomal storage disease, results from an α-galactosidase A deficiency and altered sphingolipid metabolism. An accumulation of globotriaosylsphingosine (lyso-Gb3) likely triggers the pathological cascade leading to disease phenotype. The pathogenic significance of several Fabry mutations including the R118C α-galactosidase (GLA) gene variant has been disputed. We describe three members of the same family with the R118C variant, each having documented clinical signs of FD, low residual enzyme levels, and an elevated lyso-Gb3 in one heterozygote.Determining the clinical significance of each GLA gene variant remains an ongoing challenge, with potential for inadequate treatment if the diagnosis of FD is missed. Elevated lyso-Gb3 has been shown to be the most reliable noninvasive marker of clinically relevant GLA variants. While the R118C variant will likely lead to a milder phenotype, additional genetic, epigenetic, and environmental factors can ameliorate or exacerbate the expression and impact on the resultant phenotype and associated complications. Patients affected with this variant warrant closer review and better management of disease risk factors.

A simple method for quantification of plasma globotriaosylsphingosine: Utility for Fabry disease.

Fabry disease (FD) results from impaired globotriaosylceramide (Gb3) catabolism, due to a deficiency of the lysosomal hydrolase, α-galactosidase A (α-GalA). As a direct consequence, the deacetylated derivative, globotriaosylsphingosine (lyso-Gb3), is produced and contemporary evidence exemplifies its use as a biomarker. Here we developed a simple method to enable quantification of lyso-Gb3 in just 0.01mL of plasma and explored its concentration in a cohort of 73 Australian FD patients, as well as in individuals with other sphingolipidoses. In 2000 patients without FD, but with related metabolic conditions, lyso-Gb3 returned concentrations of <5pmol/mL. In the FD cohort, 53/60 patients with classical mutations returned lyso-Gb3 concentrations≥5pmol/mL whereas only 4/13 patients with "late-onset" mutations had lyso-Gb3≥5pmol/mL. Five females with normal α-GalA activity and genetically confirmed FD returned lyso-Gb3≥5pmol/mL. The prevalence of clinically significant disease including cardiomyopathy, nephropathy and cerebrovascular disease was congruent with higher lyso-Gb3 concentrations. Repeat testing was available for 51 patients-26 undergoing enzyme replacement therapy-and concentrations of lyso-Gb3 remained unaltered throughout 6-18 months independent of sex, mutation or treatment status. Our data suggest that the optimum use of lyso-Gb3 resides in laboratory confirmation of classical FD and for monitoring at least the initial response to therapeutic intervention. There is no evidence that lyso-Gb3 can inform on clinical events.

Sleep Disturbance, Obstructive Sleep Apnoea and Abnormal Periodic Leg Movements: Very Common Problems in Fabry Disease.

OBJECTIVES: To assess the prevalence of sleep disorder(s) in males with Fabry disease and explore possible association with disease phenotype. BACKGROUND: Fabry disease, an X-linked lysosomal storage disease caused by deficiency in α-galactosidase, results in intracellular accumulation of globotriaosylceramide. It causes organ dysfunction, most significantly affecting renal, cerebrovascular and cardiovascular systems. Respiratory involvement may include obstructive lung disease, reduced diffusing capacity and thickened soft and hard palates. Patients commonly develop small-fibre sensory peripheral neuropathy manifested by acroparaesthesia and pain crises. Combined with self-reported sleep disturbance and snoring, these features suggest an increased risk of sleep disorders. METHODS: In-laboratory polysomnography (PSG) studies and sleep inventory assessments, including Epworth Sleepiness Scale (ESS), were performed in a cohort of male Fabry patients. PSGs were reviewed by a sleep physician. Sleep-disordered breathing and periodic leg movements were targeted for analysis. Associations with renal, cardiovascular and cerebrovascular function were sought. RESULTS: Twenty males underwent overnight PSG. Patient baseline characteristics included age 43.9 ± 10.7 years, BMI 24.3 ± 3.8 kg/m2, neck circumference 39.7 ± 3.3 cm and ESS 9.8 ± 5.1 (7/20, abnormal ESS >10). Abnormal periodic leg movement index (PLMI) was present in 95% (mean frequency 42.4 ± 28.5/min) and sleep-disordered breathing in 50% patients. Periodic leg movements were associated with pain and depression but not with increased cortical arousal. CONCLUSIONS: Sleep-disordered breathing and abnormal PLMI are highly prevalent in patients with FD. The presence of abnormal PLMI alone appears to have minimal impact on sleep disturbance, but is associated with depression and analgesic requirement.

Cardiovascular outcomes in Fabry disease are linked to severity of chronic kidney disease.

OBJECTIVES: Assess the impact of end-stage renal disease (chronic kidney disease stage 5 (CKD5)) on cardiovascular outcomes in patients with Fabry disease on enzyme replacement therapy. BACKGROUND: Fabry disease, an X-linked lysosomal storage disease, causes hypertrophic cardiomyopathy and cardiovascular dysfunction. METHODS: Cardiac and renal function of 25 male patients with Fabry disease were analysed at 0, 1, 2, 5, 7 and 10 years after initiation of treatment. Patients were grouped at baseline into those with CKD5 (n=10) and those without (n=15). ECG and echocardiography were performed 6 and 12 monthly, respectively, while renal function was measured yearly. RESULTS: After 10 years of treatment, cardiac and renal function in non-CKD5 patients remained unchanged. In contrast, CKD5 was associated with worse baseline cardiac parameters and progressive LV hypertrophy. LV mass index grew by 35.4±31.8 g/m(2.7) in CKD5 versus 5.7±7.9 g/m(2.7), p=0.044 in non-CKD5, predominantly due to increased interventricular septal wall thickness (7.7±5.5 mm vs 1.3±1.7 mm, p=0.003). Cardiovascular events, including sudden death, arrhythmia and pacing device insertion, occurred in 100% patients with CKD5 (21 events) and 26% non-CKD5 patients (7 events), p<0.0001. Additionally, estimated LV filling pressure (E/Ea) was significantly higher in patients having cardiovascular events (21.1±7.7 vs 12.5±4.5, p=0.008) irrespective of renal function. CONCLUSIONS: End-stage renal disease was the strongest indicator of cardiovascular disease progression in Fabry disease. Enzyme replacement initiated prior to CKD5 was associated with stability in cardiac and renal disease while patients with CKD5 showed ongoing deterioration. Additionally, E/Ea ≥15 may predict risk of cardiac events.

Antiepileptic medications increase osteoporosis risk in male fabry patients: bone mineral density in an Australian cohort.

BACKGROUND: Fabry disease (FD) is an inherited X-linked lysosomal storage disease with widespread clinical manifestations. Small prospective studies have shown increased osteopenia and osteoporosis in male FD patients. Limited information however exists about bone metabolism and osteoporosis risk factors within this group. We reviewed osteoporosis risk factors within our cohort. METHODS: A retrospective analysis of bone mineral density (BMD) results and fracture incidence in 44 patients (22 males and 22 females) was undertaken. Dual X-ray absorptiometry scans were performed at the lumbar spine, hip and femoral neck. The impact of risk factors including renal function, antiepileptic drug (AED), analgesia and vitamin D levels were assessed. RESULTS: Male FD patients had low T scores at all sites (spine -1.2 ± 1.06, hip -1.6 ± 0.9, femoral neck -2.23 ± 1.01). Female T scores showed more typical distribution (spine -0.07 ± 1.47, hip 0.02 ± 1.14, femoral neck -0.49 ± 1.31). A higher incidence of osteopenia and/or osteoporosis occurred in males versus females (spine 46.9% versus 31.8%, hip 75.5% versus 18.2% and femoral neck 86.4% versus 45.5%). Multiple regression analysis showed a 50.8% (p < 0.001) reduction in femoral neck BMD with AED usage, after adjustment for age, gender and renal function. Non-traumatic fractures occurred in 27.3% males over 205 patient-years versus 4.6% in females over 149 patient-years, p = 0.095. CONCLUSIONS: Low bone density was highly prevalent in male patients with increased incidence of non-traumatic fractures. AED usage significantly reduces BMD. Treatment to prevent BMD deterioration will depend on determining the bone turnover status.

Why older adults make more immediate treatment decisions about cancer than younger adults.

Literature relevant to medical decision making was reviewed, and a model was outlined for testing. Two studies examined whether older adults make more immediate decisions than younger adults about treatments for prostate or breast cancer in authentic scenarios. Findings clearly showed that older adults were more likely to make immediate decisions than younger adults. The research is important because it not only demonstrates the consistency of this age-related effect across disease domains, gender, ethnic groups, and prevalent education levels but begins to investigate a model to explain the effect. Major reasons for the effect focus on treatment knowledge, interest and engagement, and cognitive resources. Treatment knowledge, general cancer knowledge, interest, and cognitive resources relate to different ways of processing treatment information and preferences for immediate versus delayed decision making. Adults with high knowledge of treatments on a reliable test tended to make immediate treatment decisions, which supports the knowledge explanation. Adults with more cognitive resources and more interest tended to delay their treatment decisions. Little support was found for a cohort explanation for the relationship between age and preference for immediate medical decision making.