Clinical characterisation of sensory neuropathy with anti-FGFR3 autoantibodies.

OBJECTIVE: Sensory neuropathies (SNs) are often classified as idiopathic even if immunological mechanisms can be suspected. Antibodies against the intracellular domain of the fibroblast growth factor receptor 3 (FGFR3) possibly identify a subgroup of SN affecting mostly the dorsal root ganglion (DRG). The aim of this study was to identify the frequency of anti-FGFR3 antibodies and the associated clinical pattern in a large cohort of patients with SN. METHODS: A prospective, multicentric, European and Brazilian study included adults with pure SN. Serum anti-FGRF3 antibodies were analysed by ELISA. Detailed clinical and paraclinical data were collected for each anti-FGFR3-positive patient and as control for anti-FGFR3-negative patients from the same centres ('center-matched'). RESULTS: Sixty-five patients out of 426 (15%) had anti-FGFR3 antibodies, which were the only identified autoimmune markers in 43 patients (66%). The neuropathy was non-length dependent in 89% and classified as sensory neuronopathy in 64%, non-length-dependent small fibre neuropathy in 17% and other neuropathy in 19%. Specific clinical features occurred after 5-6 years of evolution including frequent paresthesia, predominant clinical and electrophysiological involvement of the lower limbs, and a less frequent mixed large and small fibre involvement. Brazilians had a higher frequency of anti-FGFR3 antibodies than Europeans (36% vs 13%, p<0.001), and a more frequent asymmetrical distribution of symptoms (OR 169, 95% CI 3.4 to 8424). CONCLUSIONS: Anti-FGFR3 antibodies occur in a subgroup of SN probably predominantly affecting the DRG. Differences between Europeans and Brazilians could suggest involvement of genetic or environmental factors.

Reducing the risk of misdiagnosis of indirect ELISA by normalizing serum-specific background noise: The example of detecting anti-FGFR3 autoantibodies.

Indirect enzyme-linked immunosorbent assay (ELISA) is an important diagnostic method as it enables the quantification of the presence of autoantibodies in human blood sera. However, unspecific binding of antibodies to the solid phase causes considerable serum-specific background noise (SSBN), involving the risk of false positive diagnosis. Therefore, we present a simple and concise, yet obvious proof-of-principle of a recently suggested normalization method. The method is based on subtracting SSBN by using non-coated ELISA wells as a control for each serum-of-interest. We performed ELISA to quantify anti-fibroblast growth factor receptor 3 (FGFR3) antibody levels in three positive controls (two anti-FGFR3-positive patients and a rabbit antiserum against FGFR3) and 58 negative controls (healthy blood donors). In all subjects, we found considerable unspecific reactivity which strongly varied among subjects. The conventional normalization method was not able to balance this strong SSBN, as demonstrated by 2/58 false positive healthy controls and one FGFR3-positive patient that was hidden in the noise (false negative). SSBN normalization reduced the frequency of false-positives to 0/58. Further, all three anti-FGFR3-positive sera were successfully detected and even doubled their z-score used to determine positivity. Albeit occupying more space on the ELISA plate, we strongly recommend considering this normalization method when working with blood sera. To better put the idea across to the community, we depict the SSBN issue and its solution in a graphic scheme. We conclude that SSBN normalization increases the sensitivity and specificity of indirect ELISA and thereby reduces the risk of false positive and false negative diagnosis. © 2019. Licensed under the Creative Commons [CC BY-NC 4.0 licence, https://doi.org/10.1016/j.jim.2019.01.004].

[Immune-mediated / inflammatory and hereditary neuropathies - overview and diagnostic algorithm]. / Immunvermittelte / inflammatorische und hereditäre Neuropathien ­ Übersicht und diagnostischer Algorithmus.

This paper is a practical survey of immune-mediated, inflammatory and hereditary neuropathies along with recommendations for diagnostic procedures. The large group of immune-mediated, inflammatory neuropathies includes the Guillain-Barré syndrome and chronic-inflammatory demyelinating polyradiculoneuropathy and their subtypes, vasculitic, paraneoplastic and paraproteinemic neuropathies as well as neuropathies resulting from connective tissue disorders. Besides clinical features such as time-dependent progression and distribution of sensorimotor deficits, characteristic electroneurographic findings and antibody profiles are considered. Recent studies in hereditary neuropathies reveal a prevalence of 10-28 out of 100 000 persons in Europe. Research into the genetic causes has made significant progress in the last 20 years; up to now more than 80 genes mutated in hereditary neuropathies have been identified. Besides classification into axonal, demyelinating or intermediate neuropathies based on electroneurography, distinguishing between sensorimotor, pure motor and (autonomous) sensory neuropathies as well as consideration of particular clinical features and ethnic origin can be helpful in orientating molecular genetic analysis.

A new approach to ELISA-based anti-glycolipid antibody evaluation of highly adhesive serum samples.

The enzyme-linked immunosorbent assay (ELISA) is a standard immunoassay used in measuring antibody reactivity (expressed as titers) for glycosphingolipids (GSLs) such as gangliosides and sulfoglycolipids in the sera of patients with Guillain-Barré syndrome (GBS), variants of GBS, and chronic inflammatory demyelinating polyneuropathy (CIDP). In the present study, anti-GSL antibodies were evaluated using a new formula of affinity parametric complex (APC), calculated from limiting-dilution serum assay data, followed by affinity parametric complex criterion (APCC). Using assay results based on APCC, we analyzed serum samples categorized into acute inflammatory demyelinating polyneuropathy (AIDP), acute motor-sensory axonal neuropathy (AMSAN), CIDP, CIDP with myasthenia gravis (MG), and amyotrophic lateral sclerosis (ALS). We were able to determine the affinity strength of antibodies otherwise hidden in the non-specific background activity in highly adhesive serum samples. The thin-layer chromatography (TLC)-immuno-overlay method assured us that this new method is an accurate and reliable way for evaluating anti-GSL antibodies using ELISA serum sample data.

[Ma2 antibody and multiple mononeuropathies]. / Mononeuropathie multiple et anticorps anti-Ma2.

Anti-Ma2 antibodies belong to a family of onconeuronal antibodies that target proteins expressed in brain, testis and several tumors. Previously observed in patients presenting with limbic encephalitis, they seem to be associated with several other paraneoplastic syndromes. We report the case of a 73-year-old woman presenting sensory and motor neuropathy associated with non-small-cell lung cancer who had Ma2-antibodies.

Hereditary neuropathies.

PURPOSE OF REVIEW: The purpose of this review is to help neurologists understand new concepts in hereditary neuropathies, from the clinician's point of view, in the molecular era after the burst of information regarding peripheral nerve biology. RECENT FINDINGS: Recent studies have focused on understanding the pathomechanisms involved in hereditary neuropathies. In the past year identification of new genes has slowed down since scientists have concentrated more on the function of genes causing Charcot-Marie-Tooth disease and Schwann cell-axon interactions to reveal the molecular cell biology of the disease. Animal models for the most common subtypes of human Charcot-Marie-Tooth disease are now available. SUMMARY: Rapid advances in the molecular genetics and cell biology of hereditary neuropathies have highlighted the great genetic complexity of Charcot-Marie-Tooth disease. The evolution from a simple clinical classification to a complex molecular one has not facilitated our understanding of the disease. Moreover, the new molecular classification is not simple to use as different mutations of the same gene produce a range of phenotypes. The clinicians have to look for specific clinical and electrophysiological clues to direct the patient to appropriate genetic testing.

Anti-tubulin antibodies in a sensorimotor neuropathy patient alter tubulin polymerization.

The effect of anti-tubulin antibodies present in the serum of a patient with a progressive sensorimotor neuropathy on microtubule assembly was examined. The patient's serum was reactive on immunoblots with a single band of proteins of 55-kDa from homogenates of neural tissues. Tubulin was identified as the quantitatively major component of these 55-kDa proteins. Polymerization of tubulin in vitro was significantly enhanced by the patient's serum. A monoclonal antibody to nerve-specific class III beta-tubulin precisely duplicated the immunoreactive profile of the patient's serum, while an antibody to class (I + II) beta-tubulins also reacted with tubulins in non-neural tissues. The results indicate for the first time that human antisera reactive with nerve specific beta-tubulin can alter tubulin polymerization-depolymerization dynamics.

Peripheral neuropathy associated with monoclonal IgG of undetermined significance: clinical, electrophysiologic, pathologic and therapeutic study of 14 cases.

Fourteen patients with peripheral neuropathy and monoclonal IgG of undetermined significance are reported with a retrospective study of the clinical features, electrophysiologic and sural nerve biopsy findings. There were two groups. Five patients had a relapsing chronic sensorimotor polyneuropathy with clinical (5/5), electrophysiologic (4/5) and pathologic (5/5) features compatible with chronic inflammatory demyelinating polyneuropathies (CIDP). The nine others had a slowly progressive sensory (5/9) (SPNP) or sensorimotor (4/9) (SMPNP) axonal polyneuropathy. Four patients of the first group were treated with intravenous human immunoglobulin (400 mg/kg/day for five days) with significant clinical improvement. The motor conduction velocities and distal latencies of two of these patients improved following treatment, thus matching the clinical improvement. Our results on peripheral nerve biopsies confirm the differentiation of patients with CIDP from those with SMPNP and SPNP. There was no specific immunologic serologic reactivity in any of the cases.

Coexistence of hereditary motor and sensory neuropathy type Ia and IgM paraproteinemic neuropathy.

A patient with minimal motor dysfunction dating from early childhood developed more rapidly progressive distal weakness and positive sensory symptoms due to peripheral neuropathy in the fourth decade of life. DNA analysis showed the partial duplication of chromosome 17p associated with hereditary motor and sensory neuropathy type Ia. In addition, the patient had an IgM paraproteinemia and the typical morphological features of IgM paraproteinemic neuropathy on nerve biopsy.

Class II antigen expression in peripheral neuropathies.

The expression of class II antigen was studied in sural nerve biopsies from patients with peripheral neuropathies. These included patients with chronic demyelinating polyradiculoneuropathy (CIDP), non-immune mediated neuropathies of diverse etiologies and controls without evidence of neuropathy. The major finding in CIDP was a marked increase in class II expression on Schwann cells. Endoneurial Schwann cell staining to the same degree as in CIDP was seen in diabetic symmetric proximal motor neuropathy, neuropathies associated with monoclonal gammopathies and hereditary sensory and autonomic neuropathy type 1. In the control nerves and the other non-immune mediated neuropathies class II expression was mainly restricted to endothelial and perineurial cells. Increased endoneurial expression of class II antigen was found to correlate with elevated cerebrospinal fluid (CSF) protein levels but not with other clinical variables or demyelination as defined by electrophysiologic criteria or teased fiber analysis. The increased expression of class II antigen on Schwann cells may be indicative of a breakdown in immunological tolerance but should not be used as a diagnostic marker for dysimmune neuropathies due to overlap with non-immune mediated neuropathies.

Motor neuropathy with activity of monoclonal IgM antibody to GD1a ganglioside.

A patient with motor neuropathy associated with monoclonal IgM protein is reported. Using enzyme-linked immunosorbent assays, the antibody activity of the monoclonal IgM was shown to be directed against GD1a ganglioside, a new and so far unreported specificity.

Reduced numbers of calcitonin gene-related peptide-(CGRP-) and tachykinin-immunoreactive sensory neurones associated with greater enkephalin immunoreactivity in the dorsal horn of a mutant rat with hereditary sensory neuropathy.

The mutilated foot rat is a mutant with autosomal recessive sensory neuropathy and frequent mutilation of the hindlimbs. Decreased numbers of dorsal root ganglion cells and diminished sensitivity to painful stimuli are characteristics of these animals. By use of immunocytochemistry, changes in the distributions of peptides involved in sensory and/or autonomic regulation, i.e., calcitonin gene-related peptide (CGRP), tachykinins, enkephalin and neuropeptide Y in spinal cord, dorsal root ganglia and skin of these animals, were studied. In comparison with normal litter-mate controls, the dorsal horn of mutilated foot rats contained substantially fewer CGRP- and tachykinin-immunoreactive fibres but more fibres immunoreactive for enkephalin. Many enkephalin-immunoreactive cell bodies were also found in the dorsal horn of the mutants, by contrast none were visible in control animals. Neuropeptide Y immunoreactivity was, however, unchanged in the spinal cord of the mutants. In the dorsal root ganglia of the mutants, the number of CGRP- or tachykinin-immunoreactive cells and their proportion to total neuronal numbers were significantly less in comparison with normal controls. The diameter range of CGRP- and tachykinin-immunoreactive cells shifted from small (15-25 microns) to medium size (25-45 microns) as revealed by frequency distribution histograms. The skin from the affected fore- and hindlimbs of the mutant rats, in keeping with fewer CGRP- and tachykinin-immunoreactive cells in the dorsal root ganglia, contained substantially less fibres immunoreactive for CGRP and tachykinins; a difference that was not seen in skin of unaffected areas (whiskers and snout). By contrast, neuropeptide Y-immunoreactive fibres showed a normal distribution around blood vessels and sweat glands of mutilated foot rats. The data suggest that diminished pain perception in the mutilated foot rat is related to loss of peptide-containing sensory neurones. Furthermore, the intraspinal increase of enkephalinergic neurons in the dorsal horn, concomitant with the decreased number of primary sensory neurones, may also play a contributory rôle in reducing pain thresholds.

Studies on Leber's optic neuropathy III.

Neurological investigations, HLA-typing and viral antibody studies were performed in patients with Leber's optic neuropathy (LON), in individuals at risk to develop the disease, in obligatory (female) carriers of the disease, and compared with controls. The only relevant findings were an excess of minor neurological abnormalities in patients with LON and in some individuals from the at risk group. Occasionally, an association of LON and a multiple sclerosis-like picture was observed.