A prospective, observational study of patients with uncommon distal symmetric painful small-fiber neuropathy

Magnitude of the Potential Screening Gap for Fabry Disease in Manitoba: A Population-Based Retrospective Cohort Study

Background:

Fabry disease is a rare disorder caused by the deficient activity of α-galactosidase A (GLA) that often leads to organ damage. Fabry disease can be treated with enzyme replacement or pharmacological therapy, but due to its rarity and nonspecific manifestations, it often goes undiagnosed. Mass screening for Fabry disease is impractical; however, a targeted screening program for high-risk individuals may uncover previously unknown cases.

Objective:

Our objective was to use population-level administrative health databases to identify patients at high risk of Fabry disease.

Design:

Retrospective cohort study.

Setting:

Population-level health administrative databases housed at the Manitoba Centre for Health Policy.

Patients:

All residents of Manitoba, Canada, between 1998 and 2018.

Measurements:

We ascertained the evidence of GLA testing in a cohort of patients at high risk of Fabry disease.

Methods:

Individuals without a hospitalization or prescription indicative of Fabry disease were included if they had evidence of 1 of 4 high-risk conditions for Fabry disease: (1) ischemic stroke <45 years of age, (2) idiopathic hypertrophic cardiomyopathy, (3) proteinuric chronic kidney disease or kidney failure of unknown cause, or (4) peripheral neuropathy. Patients were excluded if they had known contributing factors to these high-risk conditions. Those who remained and had no prior GLA testing were assigned a 0% to 4.2% probability of having Fabry disease depending on their high-risk condition and sex.

Results:

After applying exclusion criteria, 1386 individuals were identified as having at least 1 high-risk clinical condition for Fabry disease in Manitoba. There were 416 GLA tests conducted during the study period, and of those, 22 were conducted in individuals with at least 1 high-risk condition. This leaves a screening gap of 1364 individuals with a high-risk clinical condition for Fabry disease in Manitoba who have not been tested. At the end of the study period, 932 of those individuals were still alive and residing in Manitoba, and if screened today, we expect between 3 and 18 would test positive for Fabry disease.

Limitations:

The algorithms we used to identify our patients have not been validated elsewhere. Diagnoses of Fabry disease, idiopathic hypertrophic cardiomyopathy, and peripheral neuropathy were only available via hospitalizations and not physician claims. We were only able to capture GLA testing processed through public laboratories. Patients identified to be at high risk of Fabry disease by the algorithm did not undergo GLA testing due to a clinical rationale that we were unable to capture.

Conclusions:

Administrative health databases may be a useful tool to identify patients at higher risk of Fabry disease or other rare conditions. Further directions include designing a program to screen high-risk individuals for Fabry disease as identified by our administrative data algorithms.

Observational case-control study of small-fiber neuropathies, with regards on smoking and vitamin D deficiency and other possible causes

Introduction

Small fiber neuropathies (SFNs) are disorders of skin nerve endings inducing pruritus, burning pain, numbness, and paresthesia. The aims of this study were to search for putative etiologies of SFN and their occurrence in a cohort of patients and to compare patients with SFN to a group of patients without SFN to highlight potential factors associated with SFN.

Methods

This study was observational, retrospective, and monocentric. All patients with symptoms of SFN who underwent skin biopsies with intraepidermal nerve density counts were included. Patients with a count lower than 5 percentiles were considered to be in the SFN group. Other patients were considered to be the control group.

Results

A total of 162 patients with SFN and 161 controls were included. No cause was identified for 108 patients (61.7%). The established causes were autoimmune diseases (9.1%), diabetes or glucose intolerance (8%), medication (4%), liver disease (3.4%), and monoclonal gammopathy of undetermined significance (2.9%). Current or former smokers were more numerous in the SFN group (26.5%) than in the control group (16.1%), while vitamin D amounts were significantly lower in the SFN group than in the control group.

Discussion

Hence, tobacco smoking and vitamin D deficiency might be new putative causes of SFN.

Hereditary transthyretin amyloidosis in Sweden: Comparisons between a non-endemic and an endemic region

INTRODUCTION

Hereditary transthyretin amyloidosis (ATTRv) is endemic in northern Sweden (Västerbotten). The awareness of ATTRv amyloidosis is lower in Stockholm, a non-endemic region in Sweden. The aim of this study was to compare the possible differences in diagnostic delay, disease phenotypes, treatment and survival between a non-endemic and an endemic region in Sweden.

METHODS

The in- and outpatient diagnosis registry at the Department of Neurology at Karolinska University Hospital and the Amyloidosis Centre at University Hospital of Umeå were used to identify patients between January 2006 and November 2017.

RESULTS

In total, 21 patients in Stockholm and 134 patients in Västerbotten were included. The time between symptom onset to time-point of diagnosis was significantly longer in Stockholm vs Västerbotten. This corresponded to a longer median time between first visit at amyloidosis centre to time-point of diagnosis in Stockholm vs in Västerbotten. The most common reason for a diagnostic delay was negative tissue biopsies.

CONCLUSION

There was a diagnostic-, but no patient-delay in non-endemic Stockholm vs endemic Västerbotten. Despite a more severe neuropathic phenotype in Stockholm at the onset, the systemic affection over the course of disease and of survival seems not to be influenced by the diagnosis delay in Stockholm.

Type-I Cryoglobulinaemia Associated to Monoclonal Gammapathy of Undetermined Significance

Cryoglobulins are immunoglobulins that undergo reversible precipitation at cold temperatures. Monoclonal type-I cryoglobulinaemia is the least frequent and is associated to hematological diseases such as multiple myeloma, Waldenström's macroglobulinaemia, chronic lymphocytic leukaemia and lymphoma. We describe the case of a 60-year-old female patient, who suffered from burning pain in her feet for ten months before her admission. The patient presented intermittent distal cyanosis that progressed to digital ischaemia. She also reported paresthesia in her hands, difficulty in writing, and a 26-kg-weight loss. At the physical examination, it was identified livedo reticularis, palpable purpura, and painful ecchymotic lesions in her calves and feet. Moreover, peripheral pulses were palpable and symmetrical. It was observed an atrophy of the right first dorsal interosseous and both extensor digitorum brevis, as well as a distal bilateral apalesthesia and allodynia. Both Achilles reflexes were absent. Laboratory tests revealed anemia, high erythrosedimentation rate and C-reactive protein. Serum protein electrophoresis showed a monoclonal IgG-Kappa gammopathy. The results also evidenced the presence of Bence-Jones proteinuria. The bone marrow biopsy revealed less than 10% of plasma cells, and skin biopsy informed leukocytoclastic vasculitis. The patient was treated with high-dose intravenous steroids and cyclophosphamide. The treatment showed that the skin lesions had improved, pain disappeared and motor deficit stopped its progression.

Scientific Advances in and Clinical Approaches to Small-Fiber Polyneuropathy: A Review

IMPORTANCE

Small-fiber polyneuropathy involves preferential damage to the thinly myelinated A-delta fibers, unmyelinated C sensory fibers, or autonomic or trophic fibers. Although this condition is common, most patients still remain undiagnosed and untreated because of lagging medical and public awareness of research advances. Chronic bilateral neuropathic pain, fatigue, and nausea are cardinal symptoms that can cause disability and dependence, including pain medication dependence.

OBSERVATIONS

Biomarker confirmation is recommended, given the nonspecificity of symptoms. The standard test involves measuring epidermal neurite density within a 3-mm protein gene product 9.5 (PGP9.5)-immunolabeled lower-leg skin biopsy. Biopsies and autonomic function testing confirm that small-fiber neuropathy not uncommonly affects otherwise healthy children and young adults, in whom it is often associated with inflammation or dysimmunity. A recent meta-analysis concluded that small-fiber neuropathy underlies 49% of illnesses labeled as fibromyalgia. Initially, patients with idiopathic small-fiber disorders should be screened by medical history and blood tests for potentially treatable causes, which are identifiable in one-third to one-half of patients. Then, secondary genetic testing is particularly important for familial and childhood cases. Treatable genetic causes include Fabry disease, transthyretin and primary systemic amyloidosis, hereditary sensory autonomic neuropathy-1, and ion-channel mutations. Immunohistopathologic evidence suggests that small-fiber dysfunction and denervation, especially of blood vessels, contributes to diverse symptoms, including postexertional malaise, postural orthostatic tachycardia, and functional gastrointestinal distress. Preliminary evidence implicates acute or chronic autoreactivity in some cases, particularly in female patients and otherwise healthy children and young adults. Different temporal patterns akin to Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy have been described; here, corticosteroids and immunoglobulins, which are often efficacious for inflammatory neuropathic conditions, are increasingly considered.

CONCLUSIONS AND RELEVANCE

Because small fibers normally grow throughout life, improving contributory conditions may permit regrowth, slow progression, and prevent permanent damage. The prognosis is often hopeful for improving quality of life and sometimes for abatement or resolution, particularly in the young and otherwise healthy individuals. Examples include diabetic, infectious, toxic, genetic, and inflammatory causes. The current standard of care requires prompt diagnosis and treatment, particularly in children and young adults, to restore life trajectory. Consensus diagnostic and tracking metrics should be established to facilitate treatment trials.

Screening for Fabry disease and Hereditary ATTR amyloidosis in idiopathic small-fiber and mixed neuropathy

INTRODUCTION

In this study we assessed the value of genetic screening for Fabry disease (FD) and hereditary ATTR amyloidosis in patients with idiopathic small-fiber neuropathy (SFN) or mixed neuropathy in a clinical setting.

METHODS

This was a Nordic multicenter study with 9 participating centers. Patients with idiopathic SFN or mixed neuropathy were included. Genetic sequencing of the TTR and GLA genes was performed.

RESULTS

There were 172 patients enrolled in the study. Genetic screening was performed in 155 patients. No pathogenic mutations in the TTR gene were found. A single patient had a possible pathogenic variant, R118C, in the GLA gene, but clinical investigation showed no firm signs of FD.

DISCUSSION

Screening for hereditary ATTR amyloidosis and FD in patients with idiopathic SFN or mixed neuropathy without any additional disease-specific symptoms or clinical characteristics in a Nordic population appears to be of little value in a clinical setting. Muscle Nerve 59:354-357, 2019.

Neurologic manifestations associated with cryoglobulinemia: A single center experience

INTRODUCTION

Limited information is available describing the spectrum of neurological complications of cryoglobulinemia.

METHODS

Single center retrospective review of patients with neurologic symptoms and elevated serum cryoglobulins, with their potential association being classified as definite, possible, or unlikely using defined criteria.

RESULTS

Among 492 patients, 131 (87 classified as definite and 44 as possible) had neurologic symptoms associated with cryoglobulinemia. Common comorbidities included hepatitis C (N = 43), monoclonal gammopathy of undetermined significance (N = 20), Sjogren's syndrome (N = 17), membranoproliferative glomerulonephritis (N = 17), and systemic lupus erythematosus (N = 10). Features supporting an association between cryoglobulinemia and neurological symptoms were the presence of purpura (p < .001), positive rheumatoid factor (p = .001) and low C4 (p = .002). Common peripheral neurological diagnoses were symmetric polyneuropathy (N = 84), small fiber neuropathy (N = 25), and mononeuritis multiplex (N = 16). Central neurological manifestations were infrequent and included seizures (N = 3), posterior reversible encephalopathy syndrome (N = 2), intracerebral hemorrhage (N = 1), vasculitis (N = 1), rapidly progressive dementia (N = 1), lymphoma (N = 1), and myelitis/meningitis (N = 1). Treatments utilized included corticosteroids (N = 74), rituximab (N = 42), cyclophosphamide (N = 27), methotrexate, azathioprine, or mycophenolate mofetil (N = 28), anti-viral therapy (N = 20), plasmapheresis (N = 16), and intravenous immunoglobulin (N = 20). Neurologic symptoms associated with cryoglobulinemia remained stable or improved in 86% of patients.

CONCLUSION

This study describes a wide spectrum of patients with neurologic symptoms attributed to cryoglobulinemia and provides a framework to approach this challenging diagnosis.

[Transthyretin familial amyloid polyneuropathy]

Transthyretin family amyloid polyneuropathy (TTR-FAP) is a progressive, ultimately fatal disease. It manifests itself primarily with sensory, motor and autonomic polyneuropathy and/or cardiomyopathy and is caused by extracellular deposition of insoluble amyloid fibrils in the endoneurium. The cause of TTR-FAP is the mutation in the gene encoding transthyretin, more than 100 types of mutations are known. Given the phenotypic diversity of TTR-FAP, it is difficult for clinicians to make this diagnosis. An erroneous diagnosis is a frequent occurrence, risking the onset of an organ pathology. The paper addresses the issues of the pathogenesis, diagnosis and treatment of TTR-FAP.

Genetic Analysis of Hereditary Transthyretin Ala97Ser Related Amyloidosis

Genetic testing is the most reliable test for hereditary transthyretin related amyloidosis and should be performed in most cases of transthyretin amyloidosis (ATTR). ATTR is a rare but fatal disease with heterogeneous phenotypes; therefore, the diagnosis is sometimes delayed. With increasing attention and broader recognition on early manifestations of ATTR as well as emerging treatments, appropriate diagnostic studies, including the transthyretin (TTR) genetic test, to confirm the types and variants of ATTR are therefore fundamental to improve the prognosis. Genetic analyses with polymerase chain reaction (PCR) methods confirm the presence of TTR point mutations much more quickly and safer than conventional methods such as southern blot. Herein, we demonstrate genetic confirmation of the ATTR Ala97Ser mutation, the most common endemic mutation in Taiwan. The protocol comprises four main steps: collecting whole blood specimen, DNA extraction, genetic analysis of all four TTR exons with PCR, and DNA sequencing.