C-fibre function in systemic lupus erythematosus

Clinical, histologic, and immunologic signatures of Small Fiber Neuropathy in Systemic Lupus Erythematosus

BACKGROUND AND OBJECTIVES

Systemic Lupus Erythematosus (SLE) often causes damage to small nerve fibers, leading to distressing painful and autonomic symptoms. Despite this, Small Fiber Neuropathy (SFN) remains an underrecognized complication for SLE patients. In this cross-sectional study, we aimed to assess SFN in patients with SLE and to explore its correlations with immunologic disease features and clinical manifestations.

METHODS

We recruited 50 SLE patients (1 male to 12.5 females, aged 20-80 years) reporting painful disturbances. We conducted a comprehensive clinical and neurophysiological evaluation, using Nerve Conduction Studies and Quantitative Sensory Testing. Additionally, we carried out an extensive laboratory assessment of disease-related serological parameters. We also performed a thorough skin biopsy analysis, investigating somatic and autonomic innervation while detecting complement and inflammatory cell infiltrates within the skin.

RESULTS

Out of 50 patients, 19 were diagnosed with SFN, primarily characterized by a non-length-dependent distribution; 7 had a mixed neuropathy, with both large and small fiber involvement. Patients with SFN were younger than patients with a mixed neuropathy (p = .0143); furthermore, they were more likely to have a history of hypocomplementemia (p = .0058) and to be treated with cyclosporine A (p = .0053) compared to patients without neuropathy. However, there were no significant differences in painful and autonomic symptoms between patients with and without SFN.

DISCUSSION

This study highlights the relevant frequency of SFN with a non-length-dependent distribution among SLE patients experiencing painful symptoms. Indeed, SFN emerges as an early manifestation of SLE-related neuropathy and is closely associated with hypocomplementemia, suggesting a potential pathogenic role of the complement system. Moreover, SFN may be influenced by disease-modifying therapies. However, the precise role of SFN in shaping painful and autonomic symptoms in patients with SLE remains to be fully elucidated.

Foot and ankle characteristics in systemic lupus erythematosus: A systematic review and meta-analysis

OBJECTIVE

To determine characteristics of the foot and ankle in people with systemic lupus erythematosus (SLE).

METHODS

Medline, CINAHL, Sports-Discus, Scopus and Cochrane Library databases were searched up to January 2018. Studies reporting foot- and ankle-related outcomes in the following domains were included: vascular, neurological, musculoskeletal, cutaneous (skin and nail) or pain/function. The Quality Index tool was used to assess methodological quality. Where appropriate, odds ratio (OR) and mean difference meta-analyses were conducted for case-control studies; and pooled mean prevalence meta-analyses for studies assessing characteristics in SLE.

RESULTS

Forty-nine studies were included with mean (range) quality scores of 75% (38-100%). Twenty-three studies assessed vascular characteristics, followed by musculoskeletal (n = 16), neurological (n = 11), cutaneous (n = 5) and pain/function (n = 4). Foot and ankle characteristics in people with SLE included impaired vascular supply, abnormal nerve function, musculoskeletal pathology, skin and nail pathology, and pain and functional disability. Twenty-four studies were included in meta-analyses. Pooled OR for abnormal ankle brachial index was 3.08 for SLE compared with controls. Pooled mean difference in brachial-ankle pulse-wave velocity between SLE and controls was significant (161.39 cm/s, P = 0.004). Pooled prevalence was 0.54 for intermittent claudication, 0.50 for Raynaud's phenomenon, 0.28 for chilblains, 0.00 for gangrene, 0.30 for hallux valgus, 0.15 for onychomycosis, 0.76 for history of foot pain, and 0.36 for current foot pain.

CONCLUSION

People with SLE experience a wide range of foot and ankle manifestations. Published research highlights the impact of peripheral arterial disease, peripheral neuropathy, musculoskeletal deformity, skin and nail pathology and patient-reported foot pain and disability.

Small fiber neuropathy: a common and important clinical disorder

Small fiber neuropathy (SFN) is a neuropathy selectively involving small diameter myelinated and unmyelinated nerve fibers. Interest in this disorder has considerably increased during the past few years. It is often idiopathic and typically presents with peripheral pain and/or symptoms of autonomic dysfunction. Diagnosis is made on the basis of the clinical features, normal nerve conduction studies (NCS) and abnormal specialized tests of small nerve fibers. Among others, these tests include assessment of epidermal nerve fiber density, temperature sensation tests for sensory fibers and sudomotor and cardiovagal testing (QSART) for autonomic fibers. Unless an underlying disease is identified, treatment is usually symptomatic and directed towards alleviation of neuropathic pain.

The use of pupillometry in joint and connective tissue diseases

The central and peripheral nervous systems are variably affected in the rheumatic diseases. Automated standardized infrared pupillometry allows the safe, noninvasive assessment of the pupillary innervation. Pupillometry has already been used in studying the autonomic nervous system (ANS) in various rheumatic diseases. In systemic lupus erythematosus, the irideal parasympathetic branch of ANS was more affected then the sympathetic branch. In Sjögren's syndrome, signs of pupillary parasympathetic denervation have been reported. In rheumatoid arthritis, pupil parasympathetic dysfunction has been shown to correlate with ocular dryness. In systemic sclerosis (SSc), both sympathetic and parasympathetic irideal impairment have been demonstrated. Beside providing autonomic innervation, sensory nerves fibers are able to control iris diameter. Exogenous ocular instillation of substance P (SP), a sensory neuropeptide, can determine an omathropine-resistant, non-cholinergic myosis, acting on specific receptors present on the iris sphincter muscle. We first studied pupillary SP-ergic responsiveness in SSc, evaluating substance P (SP)-stimulated pupillary diameters by pupillometry. A higher basal and SP-stimulated myosis was found in lSSc versus both dSSc and controls, whereas no differences existed between dSSc and controls. From the literature, the pupillary parasympathetic nervous system seems to be more affected than the sympathetic branch of ANS in the rheumatic diseases characterized by an inflammatory status. However, we found in SSc both sympathetic and parasympathetic pupil control to be equally impaired. From our experience, we conclude that pupillary nervous control is differently affected in the two subsets of SSc, and that the SP-ergic system seems to be impaired only in lSSc.

Small nerve fiber involvement in systemic lupus erythematosus: a controlled study

OBJECTIVE

To determine if patients with systemic lupus erythematosus (SLE) may have a peripheral neuropathy involving unmyelinated and small, myelinated nerve fibers, by immunostaining epidermal nerve fibers (ENF) in skin biopsy samples for the panaxonal marker, protein gene product 9.5 (PGP 9.5).

METHODS

Fifteen consecutive and nonselected SLE patients and 15 age- and sex-matched controls were included in the study. The age of the patients ranged from 25 years to 65 years, with a mean +/- SD age of 47.3 +/- 10.2 years and a disease duration of 2-28 years (mean +/- SD 14.8 +/- 8.6 years). Two 3-mm skin biopsy samples were obtained with a punch needle approximately 10 cm superior to the lateral malleolus of the right leg and immunostained with 0.1% rabbit polyclonal antibodies to human PGP 9.5. The number of ENF per millimeter was counted and recorded as the mean +/- SD of counts in six 50-microm sections, 3 from each of the 2 biopsy samples.

RESULTS

The mean number of ENF per mm in patients with SLE was 8.0 +/- 1.5 (range 5.0-9.9), while the matched controls had 12.2 +/- 3.8 ENF per mm (range 6.8-18.6) (P = 0.0006).

CONCLUSION

This study indicates that a small fiber involvement in patients with SLE may be responsible for the prevalent neuropathic symptoms and impaired warm sense that is observed in such patients.

Peripheral neuropathy in systemic lupus erythematosus--a longitudinal study

OBJECTIVE

Peripheral neuropathy (PN) is reported to occur in 5-27% of patients with systemic lupus erythematosus (SLE) mostly as a length-dependent sensorimotor axonopathy. Studies over time have not been performed. Design - Longitudinal study.

SUBJECTS AND METHODS

Thirty-three Caucasian SLE patients consented to participate in the study and were subjected to clinical examination, laboratory tests, and nerve conduction velocity (NCV) studies. At the follow-up 7 years later, 7 patients (21%) were dead, 4 refused to participate, and 2 did not want to perform NCV studies. Twenty patients were thus available for longitudinal study.

RESULTS

When all SLE patients were considered on a group basis at follow-up, 8 (33%) out of 24 NCV parameters showed significant deterioration despite correction for time, while 16 (67%) were unchanged. Analysis of change from baseline showed that, except for F-responses, several NCV changes were highly dependent (negative regression coefficients) on baseline levels at start of study. No demographic, laboratory, or disease associated quantitative factor was associated with these changes in NCV parameters over time. Nor was a consistent effect on NCV parameters from any qualitative demographic or disease associated factor confirmed by Repeated Measures ANOVA analyses.

CONCLUSIONS

A modest progressive neuropathic process exists in patients with SLE. Important is also the finding that, over time, the abnormalities of NCV parameters fluctuate in the individual patients, and the impairments are not necessarily irreversible. This study also shows no association to medication, demographic-, or other disease associated factors.

Neuromuscular complications of connective tissue diseases

The connective tissue diseases, such as rheumatoid arthritis, Sjögren's syndrome, systemic lupus erythematosus, systemic sclerosis, and vasculitis, may cause various disorders of the peripheral nervous system. In this review, the clinical effects of the connective tissues diseases on nerve and muscle are examined with particular attention to mononeuritis multiplex, distal symmetric neuropathy, fulminant motor neuropathy, compression neuropathy, sensory neuronopathy, and trigeminal sensory neuropathy.