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To the Editor: In the review article on inflammatory muscle diseases, Dalakas (April 30 issue) 1 outlines four major subtypes. In 1998, Gherardi et al. described a new but underrecognized clinical variant, called macrophagic myofasciitis, 2 a condition that presents as diffuse myalgias of variable intensity associated with chronic fatigue. Myalgia predominantly affects the lower limbs and is often aggravated by exercise. It is associated with arthralgias in 50 to 60% of patients, as well as fever in 30% of patients. 3 Results on electromyography may be myopathic, and creatine kinase levels may be elevated in up to 50% of patients. 4 This disease . . .

Summary Background The high variability in clinical manifestations of Fabry disease can lead to delays between symptom onset and correct diagnosis, and between correct diagnosis and initiation of enzyme replacement therapy. We investigated whether these delays have improved in recent years. Methods Data were analysed from the Fabry Outcome Survey (FOS; Shire; extracted August 2013) for “index patients”, defined as the first patient diagnosed with Fabry disease from a family with several or no additional members registered in FOS. Results Periods analysed: 2001‐2006 vs. 2007‐2013, in patients overall and from Europe vs. the rest of the world (ROW). Overall, 598 patients were diagnosed within the study periods. Median age (95% CI) at symptom onset in 2001‐2006 and 2007‐2013 was 7.0 (5.0‐11.0) and 9.0 (6.0‐11.0) in children, and 21.0 (15.0‐28.0) and 31.0 (26.0‐35.0) in adults, respectively. Overall, the delay in diagnosis did not improve, despite showing a trend towards earlier diagnosis in adults (median 14.0 [95% CI 9.0‐20.0] vs. 10.5 [8.0‐13.0] years) and children (5.0 [1.0‐9.0] vs. 4.0 [0.0‐8.0] years). In contrast, the delay in treatment onset significantly decreased from 2001‐2006 to 2007‐2013 in children (4.3 [2.0‐7.0] vs. 1.0 [0.8‐1.4] year; P<.001) and adults (2.1 [1.3‐3.2] vs. 0.9 [0.8‐1.1] years; P<.001). Geographically, the delay in treatment onset significantly decreased in the ROW among children (5.3 [4.2‐8.0] vs. 1.0 [0.8‐1.4] year; P<.001) and adults (5.4 [4.8‐6.0] vs. 1.1 [0.9‐1.1] years; P<.001), but it did not change in Europe. Conclusion We found that the delay in diagnosis has not improved substantially whereas the delay in treatment onset has improved in recent years.

The clinical use of agalsidase alfa as enzyme replacement therapy (ERT) for Fabry disease (FD) has spread since 2001, and a large body of evidence of its effectiveness has been collected. This review presents the clinical and laboratory results achieved with agalsidase alfa, which has been published in the literature. Agalsidase alfa infusion slows down or stops the progression of renal damage, expressed by reduction or stabilization of the annual decline of the glomerular filtration rate; yearly decrease of glomerular filtration rate (slope) sometimes is reduced until its stabilization. ERT prevents or reduces the occurrence of hypertrophic cardiomyopathy or slows the increase over time if it is already present. Moreover, regarding neurological manifestations, ERT improves neuropathic pain and quality of life, and recent data indicated that it may also prevent the burden of cerebrovascular disease. In addition to ERT's clinical benefits, crucial topics like the most appropriate time to start therapy and the role of anti-drug antibodies (ADA) are analyzed. Treatment with agalsidase alfa in patients with FD substantially improves their outcomes and enhances their quality of life in patients with FD.

Background Patient registries provide long-term, real-world evidence that aids the understanding of the natural history and progression of disease, and the effects of treatment on large patient populations with rare diseases. The year 2021 marks the 20th anniversary of the Fabry Outcome Survey (FOS), an international, multicenter, observational registry (NCT03289065). The primary aims of FOS are to broaden the understanding of Fabry disease (FD), an X-linked lysosomal storage disorder, and to improve the clinical management of affected patients. Here, we review the history of FOS and the analyses and publications disseminated from the registry, and we discuss the contributions FOS studies have made in understanding FD. Results FOS was initiated in April 2001 and, as of January 2021, 4484 patients with a confirmed diagnosis and patient informed consent have been enrolled from 144 centers across 26 countries. Data from FOS have been published in nearly 60 manuscripts on a wide variety of topics relevant to FD. Analyses of FOS data have investigated the long-term effectiveness and safety of enzyme replacement therapy (ERT) with agalsidase alfa and its effects on morbidity and mortality, as well as the benefits of prompt and early treatment with agalsidase alfa on the progression of cardiomyopathy and the decline in renal function associated with FD. Based on analyses of FOS data, ERT with agalsidase alfa has also been shown to improve additional signs and symptoms of FD experienced by patients. FOS data analyses have provided a better understanding of the natural history of FD and the specific populations of women, children, and the elderly, and have provided practical tools for the study of FD. FOS has also provided methodology and criteria for assessing disease severity which contributed to the continuous development of medical practice in FD and has largely improved our understanding of the challenges and needs of long-term data collection in rare diseases, aiding in future rare disease real-world evidence studies. Conclusion FOS over the last 20 years has substantially increased the scientific knowledge around improved patient management of FD and continues to expand our understanding of this rare disease.

Background Fabry disease and Gaucher disease are rare genetic disorders characterized by defective degradation of glycosphingolipids caused by enzymatic deficiencies in α–galactosidase A and β–glucocerebrosidase, respectively, and often require life-long treatment. Treatment options for these disorders include replacing the deficient enzymes via enzyme replacement therapy (ERT). Agalsidase alfa for Fabry disease and velaglucerase alfa for Gaucher disease are two ERT options with demonstrated efficacy, safety, and tolerability. ERT infusions administered by a health care provider (HCP) in the clinic/hospital, or at the patient’s home are considered HCP-supported infusions. Self-administration of ERT (by patient, partner, relative, or caregiver) is optional in patients who tolerate the HCP-supported infusions at home and have a suitable home environment. This analysis explored the safety profiles of self-administered agalsidase alfa (202 patients) and velaglucerase alfa (30 patients) versus HCP-supported infusions using data from the Fabry Outcome Survey (FOS) and Gaucher Outcome Survey (GOS) registries. Results The frequency of infusion-related reactions (IRRs) adverse events (AEs) recorded in the two registries was lower in patients self-administering (FOS: 4.5%, GOS: 0%) versus patients receiving HCP-supported infusions (FOS: 13.6%, GOS: 1.6%). In the FOS registry, AE rates per 100 patient-years (100PY) of follow-up were similar between the self-administration (7.99) and HCP-supported infusion (6.78) groups. In patients self-administering agalsidase alfa, cardiac disorders were the most frequently reported AEs (19 [9.4%] patients) and serious AEs (12 [5.9%]) and gastrointestinal disorders were the most frequently reported IRRs (3 [1.5%]). In the GOS registry, AE rates per 100PY were similar between self-administration (4.97) and HCP-supported infusion (4.67) groups. In patients self-administering velaglucerase alfa, skin and subcutaneous disorders (4 [13.3%]) and infections and infestations (2 [6.7%]) were the most reported AEs and serious AEs, respectively, and no IRRs were reported. Conclusions These findings suggest that self-administration of agalsidase alfa or velaglucerase alfa infusions are not associated with additional safety risks compared with HCP-supported infusions and are a suitable option for qualifying patients. Further research is warranted to support these findings and to explore further the long-term safety and efficacy of ERT self-administration. FOS trial registration: ClinicalTrials.gov, NCT03289065. Registered 01 April 2001, https://clinicaltrials.gov/study/NCT03289065 . GOS trial registration: ClinicalTrials.gov, NCT03291223. Registered 27 July 2010, https://classic.clinicaltrials.gov/ct2/show/NCT03291223 .

ObjectiveHereditary myopathy with early respiratory failure (HMERF) is caused by titin A-band mutations in exon 344 and considered quite rare. Respiratory insufficiency is an early symptom. A collection of families and patients with muscle disease suggestive of HMERF was clinically and genetically studied.MethodsAltogether 12 new families with 19 affected patients and diverse nationalities were studied. Most of the patients were investigated using targeted next-generation sequencing; Sanger sequencing was applied in some of the patients and available family members. Histological data and muscle MRI findings were evaluated.ResultsThree families had several family members studied while the rest were single patients. Most patients had distal and proximal muscle weakness together with respiratory insufficiency. Five heterozygous TTN A-band mutations were identified of which two were novel. Also with the novel mutations the muscle pathology and imaging findings were compatible with the previous reports of HMERF.ConclusionsOur collection of 12 new families expands mutational spectrum with two new mutations identified. HMERF is not that rare and can be found worldwide, but maybe underdiagnosed. Diagnostic process seems to be complex as this study shows with mostly single patients without clear dominant family history.

ObjectivesThe PRoposing Early Disease Indicators for Clinical Tracking in Fabry Disease (PREDICT-FD) initiative aimed to reach consensus among a panel of global experts on early indicators of disease progression that may justify FD-specific treatment initiation.Design and settingAnonymous feedback from panellists via online questionnaires was analysed using a modified Delphi consensus technique. Questionnaires and data were managed by an independent administrator directed by two non-voting cochairs. First, possible early indicators of renal, cardiac and central/peripheral nervous system (CNS/PNS) damage, and other disease and patient-reported indicators assessable in routine clinical practice were compiled by the cochairs and administrator from panellists’ free-text responses. Second, the panel scored indicators for importance (5-point scale: 1=not important; 5=extremely important); indicators scoring ≥3 among >75% of panellists were then rated for agreement (5-point scale: 1=strongly disagree; 5=strongly agree). Indicators awarded an agreement score ≥4 by >67% of panellists achieved consensus. Finally, any panel-proposed refinements to consensus indicator definitions were adopted if >75% of panellists agreed.ResultsA panel of 21 expert clinicians from 15 countries provided information from which 83 possible current indicators of damage (kidney, 15; cardiac, 15; CNS/PNS, 13; other, 16; patient reported, 24) were compiled. Of 45 indicators meeting the importance criteria, consensus was reached for 29 and consolidated as 27 indicators (kidney, 6; cardiac, 10; CNS/PNS, 2; other, 6; patient reported, 3) including: (kidney) elevated albumin:creatinine ratio, histological damage, microalbuminuria; (cardiac) markers of early systolic/diastolic dysfunction, elevated serum cardiac troponin; (CNS/PNS) neuropathic pain, gastrointestinal symptoms suggestive of gastrointestinal neuropathy; (other) pain in extremities/neuropathy, angiokeratoma; (patient-reported) febrile crises, progression of symptoms/signs. Panellists revised and approved proposed chronologies of when the consensus indicators manifest. The panel response rate was >95% at all stages.ConclusionsPREDICT-FD captured global opinion regarding current clinical indicators that could prompt FD-specific treatment initiation earlier than is currently practised.

Guillain–Barré syndrome (GBS) is a rare, but potentially fatal, immune-mediated disease of the peripheral nerves and nerve roots that is usually triggered by infections. The incidence of GBS can therefore increase during outbreaks of infectious diseases, as was seen during the Zika virus epidemics in 2013 in French Polynesia and 2015 in Latin America. Diagnosis and management of GBS can be complicated as its clinical presentation and disease course are heterogeneous, and no international clinical guidelines are currently available. To support clinicians, especially in the context of an outbreak, we have developed a globally applicable guideline for the diagnosis and management of GBS. The guideline is based on current literature and expert consensus, and has a ten-step structure to facilitate its use in clinical practice. We first provide an introduction to the diagnostic criteria, clinical variants and differential diagnoses of GBS. The ten steps then cover early recognition and diagnosis of GBS, admission to the intensive care unit, treatment indication and selection, monitoring and treatment of disease progression, prediction of clinical course and outcome, and management of complications and sequelae.

Adult polyglucosan body disease is a rare genetic condition caused by biallelic pathogenic variants in GBE-1 gene. Affected patients typically have urinary dysfunction, progressive gait disturbance and cognitive impairment. We report a 63-year-old woman with urinary incontinence, walking difficulty and episodes of forgetfulness. She had symmetrical limb weakness with upper motor neurone signs, distal sensory loss and a broad-based ataxic gait. MR scans of the brain and spine showed white matter changes with cerebellar and spinal cord atrophy. Sural nerve biopsy identified intra-axonal polyglucosan bodies. A multigene panel test identified a GBE-1 pathogenic variant, confirming the diagnosis of adult polyglucosan body disease. This case emphasises the importance of considering rare genetic disorders in people with autonomic dysfunction, mixed upper and lower motor neurone signs, peripheral neuropathy and cognitive impairment.