NMO-IgG in the diagnosis of neuromyelitis optica

Current therapeutic recommendations in multiple sclerosis

Recent clinical studies in multiple sclerosis have provided new data on glatiramer acetate, interferon-beta preparations and natalizumab, which will have important implications for optimising patient care. Once a diagnosis has been made with confidence, early initiation of immunotherapy is warranted because of the presence of continuous inflammatory disease activity. Approval for therapy in patients with a clinically isolated syndrome has been granted to several first-line treatments, and most recently to glatiramer acetate. The utility of systematic frequent MRI monitoring of disease activity and response to therapy is not yet clearly established. Treatment efficacy after initiating therapy at the first demyelinating episode has to be followed carefully and re-evaluated whenever necessary. The occurrence of further relapses, confirmed disability progression or MRI evidence of persistent or aggravated disease activity would be regarded as evidence for an inadequate treatment response. However, limitations of clinical scores in faithfully reflecting disease activity at all times, as well as uncertainties about the discriminatory capacity of surrogate measures such as MRI, need to be clarified before clear-cut recommendations on treatment failure can be advocated. Escalation therapy is reserved for patients presenting with 'aggressive disease', which can be operationally defined as the occurrence of two severe relapses within twelve months, together with either MRI evidence for persistent disease activity or a two-point progression of disability on the EDSS.

A new Purkinje cell antibody (anti-Ca) associated with subacute cerebellar ataxia: immunological characterization

We report on a newly discovered serum and cerebrospinal fluid (CSF) reactivity to Purkinje cells (PCs) associated with subacute inflammatory cerebellar ataxia. The patient, a previously healthy 33-year-old lady, presented with severe limb and gait ataxia, dysarthria, and diplopia two weeks after she had recovered from a common cold. Immunohistochemical studies on mouse, rat, and monkey brain sections revealed binding of a high-titer (up to 1:10,000) IgG antibody to the cerebellar molecular layer, Purkinje cell (PC) layer, and white matter. The antibody is highly specific for PCs and binds to the cytoplasm as well as to the inner side of the membrane of PC somata, dendrites and axons. It is produced by B cell clones within the CNS, belongs to the IgG1 subclass, and activates complement in vitro. Western blotting of primate cerebellum extract revealed binding of CSF and serum IgG to an 80-97 kDa protein. Extensive control studies were performed to rule out a broad panel of previously described paraneoplastic and non-paraneoplastic antibodies known to be associated with cerebellar ataxia. Screening of >9000 human full length proteins by means of a protein array and additional confirmatory experiments revealed Rho GTPase activating protein 26 (ARHGAP26, GRAF, oligophrenin-1-like protein) as the target antigen. Preadsorption of the patient's serum with human ARHGAP26 but not preadsorption with other proteins resulted in complete loss of PC staining. Our findings suggest a role of autoimmunity against ARHGAP26 in the pathogenesis of subacute inflammatory cerebellar ataxia, and extend the panel of diagnostic markers for this devastating disease.

B cells and antibodies in MS

Increasing research activities on humoral immune responses involved in the immunopathogenesis of multiple sclerosis (MS) led to a revival of the importance of B cells and antibodies in MS. B cells seem now to play various immunopathogenetic roles in the initiation and propagation of inflammatory demyelinating processes at different disease stages of MS. The biological activities of antibodies in MS is, in general, still less known, although it emerges that antibodies are specifically involved in demyelination or, at least, mirror tissue destruction in the central nervous system. Finally, there is growing evidence that treatments, which specifically target B cells and/or antibodies, are effective in MS and its variants neuromyelitis optica (NMO). This chapter therefore aims to summarize the present knowledge and to outline future directions about the role of B cells and antibodies in research and therapy of MS and NMO.

Recurrent neuromyelitis optica in Brazilian patients: clinical, immunological, and neuroimaging characteristics

Neuromyelitis optica has not been thoroughly studied in Brazilian patients following the discovery of NMO-IgG and its specific antigen aquaporin-4. In this study we aimed to describe the clinical NMO-IgG immunological status and neuroimaging characteristics of recurrent neuromyelitis optica in a series Brazilian patients. We undertook a retrospective study of 28 patients with recurrent neuromyelitis optica, according to 1999 Wingerchuk’s diagnostic criteria. Data on NMO-IgG status, clinical features, and MRI findings were analyzed. Three men and 25 women were evaluated. Median age at onset of disease was 26 years (range 7—55); median time of follow-up was 7 years (range 2—14). The mean time elapsed between the first and the second attack was 17 months (median 8.5; range 2—88). NMO-IgG was detected in 18 patients (64.3%). Four patients died due to respiratory failure. Most patients presented with cervical (36%) and cervical-thoracic myelitis (46.4%). Holocord lesion was the most common pattern of involvement (50%) on the axial plane. We did not find a statistical association between myelitis extension and NMO-IgG result. Our series of Brazilian patients showed a younger age of onset than previously reported. In our series, in contrast to previous reports, there was no correlation between the extension of myelitis and NMO-IgG positivity.

The idiotype connection: linking infection and multiple sclerosis

B cells present idiotopes (Id) from their B cell receptor to Id-specific CD4(+) T cells. Chronic Id-driven T-B cell collaboration can cause autoimmune disease in mice. We propose that Id-driven T-B cell collaboration mediates the development of multiple sclerosis by perpetuating immune responses initiated against infectious agents. During germinal centre reactions, B cells express a multitude of mutated Ids. While most mutations lead to decreased affinity and deletion of the B cell, some B cells could be rescued by Id-specific T cells. Such Id-connected T-B cell pairs might initiate inflammatory foci in the central nervous system. This model may explain the intrathecal synthesis of low-avidity IgG against viruses, and the synthesis of oligoclonal IgG with unknown specificity in multiple sclerosis.

Antibody-negative neuromyelitis optica with heavy B-cell infiltration

There are several distinct clinical phenotypes of inflammatory demyelinating diseases of the central nervous system. In classical multiple sclerosis (MS) there are varied pathological patterns, possibly with differences in pathogenesis. Neuromyelitis optica (NMO) is often associated with a specific antibody, suggesting a distinct pathogenesis. We report a case of a young Caucasian male who presented with right hemiparesis secondary to a left fronto-parietal inflammatory brain lesion, which improved over years leaving minimal deficit. Seventeen years later he re-presented with a progressive tetraparesis secondary to cervical myelitis that did not respond to treatment. The NMO antibody was not detected and neuropathological examination was unusual with evidence of a persistent B-cell inflammatory response in the cord. Although having some of the clinical features of NMO, this case presented novel clinico-pathological features that do not easily fit into current MS subtypes.

Optical coherence tomography helps differentiate neuromyelitis optica and MS optic neuropathies

OBJECTIVE

To evaluate the retinal nerve fiber layer (RNFL) thickness and macular volume in neuromyelitis optica (NMO) spectrum patients using optical coherence tomography (OCT).

BACKGROUND

OCT can quantify damage to retinal ganglion cell axons and can identify abnormalities in multiple sclerosis and optic neuritis (ON) eyes. OCT may also be useful in the evaluation of patients with NMO.

METHODS

OCT and visual function testing were performed in 26 NMO spectrum patients with a history of ON, 17 patients with isolated longitudinally extensive transverse myelitis (LETM) without ON, 378 patients with relapsing-remitting multiple sclerosis (RRMS), and 77 healthy controls at 2 centers.

RESULTS

Substantial RNFL thinning was seen in NMO ON eyes (63.6 microm) relative to both RRMS ON eyes (88.3 microm, p < 0.0001) and control eyes (102.4 microm, p < 0.0001). A first episode of ON was estimated to cause 24 microm more loss of RNFL thickness in NMO than RRMS. Similar results were seen for macular volume. ON also was associated with more severe visual impairment in NMO spectrum patients than in RRMS patients. Eyes in the LETM group and unaffected NMO eyes were not significantly different from controls, though conclusions about these subgroups were limited by small sample sizes.

CONCLUSIONS

Optical coherence tomography (OCT) shows more severe retinal damage after optic neuritis (ON) episodes in neuromyelitis optica (NMO) than in relapsing-remitting multiple sclerosis. Identification of substantial retinal nerve fiber layer loss (>15 microm) after ON in a non-multiple sclerosis patient should prompt consideration of an NMO spectrum condition. OCT may be a useful tool for the evaluation of patients with NMO.

Anti-endothelial serum antibodies in a patient with Susac's syndrome

BACKGROUND

Susac's syndrome (SS) is a rare arteriopathy affecting the microvasculature of the brain, retina, and inner ear, resulting in encephalopathy, branch retinal artery occlusion and hearing loss. Anecdotal reports exist on SS being associated with a humoral immune response against endothelial cells. However, no original data has ever been published.

OBJECTIVE

To analyze serum and CSF from a patient with SS for the presence of CNS auto-antibodies and, if present, to further characterize such antibodies immunologically.

METHODS

Serum and CSF samples were examined by indirect immunofluorescence on adult mouse cerebrum, cerebellum, brain stem, and inner ear tissue sections, and IgG subclasses were determined.

RESULTS

Anti-endothelial antibodies were found at a titre of 1:960 in serum but not CSF. Antibodies belonged to the complement activating IgG1 subclass. Glucocorticoid treatment resulted in a decrease of titres (1:480), though the antibodies remained clearly detectable.

CONCLUSION

Our finding of anti-endothelial cell antibodies in a patient with SS is important in the light of previous pathological data suggesting that SS is associated with endothelial damage. Larger serological studies are now warranted to assess systematically the frequency and relevance of auto-antibodies in SS.

Absence of neuromyelitis optica IgG antibody in an active relapsing-remitting multiple sclerosis population

BACKGROUND

Neuromyelitis optica (NMO, Devic disease) had been defined clinically until a novel autoantibody directed against the aquaporin-4 channel (NMO IgG antibody) was identified. Although previous studies have demonstrated that the NMO IgG antibody is not present in patients with multiple sclerosis (MS), these studies may have been biased by the inclusion of patients with inactive MS. We resolved to test for NMO antibody in a population of patients with active relapsing-remitting (RR) MS.

METHODS

A total of 130 patients with RRMS previously enrolled in phase I (n = 26) and phase II (n = 104) trials of rituximab therapy were tested for serum NMO IgG antibody at the Mayo Clinic Neuroimmunology Laboratory by indirect immunofluorescence on a substrate of mouse central nervous system tissue. Serum samples were obtained at baseline before initiation of therapy. All patients had experienced at least one relapse in the year before study entry and had not received treatment with immunomodulatory agents for at least 2 months.

RESULTS

None of the 130 patients with active RRMS tested positive for NMO IgG antibody.

CONCLUSIONS

Our findings indicate that anti-aquaporin-4 immunoreactivity is unlikely to play a role in the pathogenesis of RRMS and support the results of previous studies suggesting that that the NMO IgG antibody is specific for NMO. Similar studies in a larger cohort will be necessary to fortify our conclusions.

Neuromyelitis optica-IgG in idiopathic inflammatory demyelinating disorders amongst Hong Kong Chinese

BACKGROUND

Idiopathic inflammatory demyelinating disorders (IIDD) affect the central nervous system. In classical multiple sclerosis (CMS), brain, optic nerves [optic neuritis (ON)] and spinal cord [acute transverse myelitis (ATM)] are affected. In neuromyelitis optica (NMO), optic nerves and spinal cord are predominantly affected. NMO-IgG, an autoantibody targeting aquaporin-4, is a marker for NMO. We studied the frequency and clinical relevance of NMO-IgG seropositivity in IIDD patients.

METHODS

Neuromyelitis optica-IgG was detected by indirect immunofluorescence using primate cerebellum.

RESULTS

Neuromyelitis optica-IgG was detected in six of 10 NMO patients (60%), six of 10 idiopathic relapsing transverse myelitis (IRTM) patients (60%), two of nine idiopathic relapsing ON patients (22%), one of 11 patients (9%) having single ON attack, one of 30 CMS patients (3%), and none of patients having single ATM attack or controls. Comparing NMO-IgG seropositive (n = 12) with NMO-IgG seronegative (n = 8) patients having NMO or IRTM, NMO-IgG seropositivity was associated with a higher relapse rate in first 2 years, 1.5 and 0.6 attacks/year for seropositive and seronegative groups respectively (P = 0.006), and non-significant trend towards more severe ON and myelitis with poorer clinical outcome.

CONCLUSION

Neuromyelitis optica -IgG facilitates diagnosis of NMO spectrum disorders. NMO-IgG seropositivity is associated with higher relapse rate in first 2 years.

Neuromyelitis optica positive antibodies confer a worse course in relapsing-neuromyelitis optica in Cuba and French West Indies

Background

In Caucasian populations Neuromyelitis Optica (NMO-IgG) antibody has been detected in 27.1% / 78.2% of patients with relapsing-NMO (R-NMO). The prevalence reported for the disease in the Caribbean is 3.1/100,000 in the French West Indies (FWI) and 0.52 /100,000 in Cuba, but the NMO antibody status is unknown.

Objective

To assess the NMO-IgG antibody status of Cuban/FWI RNMO patients, comparing with European cases tested at the same laboratories.

Methods

Serum NMO-IgG antibodies were assayed in 48 R-NMO patients (Wingerchuck´s 1999 criteria): Cuba (24)/FWI (24), employing Lennon et al´s method. We compared the demographic, clinical, disability and laboratory data between NMO-IgG +/- patients. All the data were reviewed and collected blinded to the NMO-IgG status.

Results

Seropositivity of the NMO-IgG antibody demonstrated a lower rate in the Caribbean (33.3%), as compared with Caucasian patients from Spain/Italy (62.5%) and France (53.8%). Caribbean patients with NMO-IgG (+) displayed more attacks, more spinal attacks and a higher EDSS than NMO-IgG (-) cases, while brain and spinal cord MRI lesions were more frequent during remission, with more vertebral segments, more gray, white matter and holocord involvement.

Conclusions

NMO IgG positive antibodies in NMO patients had a lower rate in the Caribbean area – where the population has a predominant African ancestry – than in Caucasian Europeans, suggesting the influence of a possible ethnic factor in the pathogenesis of the disease, but they confer a worse course with more attacks, more disability and MRI lesions.

Neuromyelitis optica in Brazil: a study on clinical and prognostic factors

Objectives

To describe the clinical characteristics of patients with relapsing neuromyelitis optica (NMO) from a tertiary care center in Brazil and compare the groups with normal and abnormal brain magnetic resonance imaging (MRI).

Methods

Retrospective review of 41 patients followed at the Neuroimmunology Clinic of the Federal University of São Paulo, Brazil, from 1994 to 2007.

Results

All patients had relapsing-remitting optic-spinal disease, long extending spinal cord lesions, and brain MRI not meeting Barkhof criteria for multiple sclerosis (MS), thus fulfilling the 1999 and 2006 Wingerchuck criteria for NMO. Mean follow-up time was 52 months; mean age of onset was 32.6 years. The mean relapse rate (RR) and progression index (PI) were 1.0 and 0.9, respectively. Twenty-four patients had brain lesions not compatible with MS on MRI, and there were no statistical differences on PI and RR between patients who had brain lesions and patients who did not. Incomplete recovery, but not the type of first relapse, correlated with a worse prognosis. Seventeen patients were tested for NMO-IgG (anti-aquaporin-4 antibody) with 41% positivity.

Conclusions

In this series, we did not find a statistical difference of disease progression between patients with and without brain lesions, suggesting that the presence of brain abnormalities is not a marker of disease severity.

Neuromyelitis optica and asian phenotype of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS), whereas neuromyelitis optica (NMO) is an inflammatory disease of the CNS selectively affecting the optic nerves and spinal cord. The pathological hallmark in MS is sharply demarcated demyelinating plaque with axons relatively preserved, whereas in NMO both axons and myelin are involved, resulting in necrotic cavitation. The nosological position of NMO has long been a matter of debate. In Asians, MS is rare; however, when it appears, the selective but severe involvement of the optic nerves and spinal cord is characteristic. This form, termed opticospinal MS (OSMS), has similar features to those of the relapsing form of NMO in Western populations. Recent discovery of a specific immunoglobulin G (IgG) against NMO, designated NMO-IgG, suggests that NMO is a distinct disease entity with a fundamentally different etiology from that of MS. Because NMO-IgG has been reported to be present in about 50%-60% of OSMS patients with longitudinally extensive spinal cord lesions (LESCLs), OSMS in Asians has been suggested to be the same entity as NMO. About half of the patients with the anti-aquaporin 4 (AQP4) antibody demonstrate brain lesions fulfilling the Barkhof criteria, whereas OSMS patients without the anti-AQP4 antibody show significantly fewer brain lesions. These findings indicate that the mechanism of LESCLs in Asians is heterogeneous, both related and unrelated to anti-AQP4 antibody, and that the disease condition with anti-AQP4 antibody does not completely overlap OSMS in Asians. This review discusses possible mechanisms for OSMS and anti-AQP4 autoimmune syndrome of the CNS.

Spectrum of pediatric neuromyelitis optica

OBJECTIVE

Our goal was to describe the spectrum of clinical phenotypes, laboratory and imaging features, and treatment in pediatric patients with neuromyelitis optica.

PATIENTS AND METHODS

The study consisted of a retrospective chart review of patients followed in a pediatric multiple sclerosis center with a diagnosis of neuromyelitis optica spectrum disorder.

RESULTS

Nine patients with neuromyelitis optica spectrum disorders were included, all of whom were female. There were 4 black children, 2 Latin American children, 2 white children, and 1 child of mixed Latin American/white heritage. Median age at initial attack was 14 years (range: 1.9-16 years). Median disease duration was 4 years (range: 0.6-9 years). Tests for neuromyelitis optica immunoglobulin G were positive for 7 patients. Eight patients had transverse myelitis and optic neuritis, and 1 patient had longitudinally extensive transverse myelitis without optic neuritis but had a positive neuromyelitis optica immunoglobulin G antibody titer. Cerebral involvement on MRI was found in all subjects, 5 of whom were symptomatic with encephalopathy, seizures, hemiparesis, aphasia, vomiting, or hiccups. Immunosuppressive therapy reduced attack frequency and progression of disability.

CONCLUSIONS

Pediatric neuromyelitis optica has a diverse clinical presentation and may be difficult to distinguish from multiple sclerosis in the early stages of the disease. The recognition of the broad spectrum of this disease to include signs and symptoms of brain involvement is aided by the availability of a serum biomarker: neuromyelitis optica immunoglobulin G. Early diagnosis and immunosuppresive treatment may help to slow the accumulation of severe disability.

Pelvic pain as an unusual first presentation of a demyelinating disease

Pelvic pain as the presenting symptom of demyelinating disease is rare. We report on a 49-year-old female patient that initially had symptoms of pain and anesthesia in the perineum. Symptoms later evolved to include both lower and upper extremity weakness and were associated with enhancing spinal cord lesions on MRI. Recognizing that the patient's disease was localized only to the spinal cord led to an eventual serological diagnosis of neuromyelitis optica (Devic's disease), a demyelinating syndrome that is now considered distinct from multiple sclerosis and that primarily affects the spinal cord and optic nerves. Pelvic pain is an unusual first presentation of this illness. Additionally, this case illustrates the challenges of establishing a diagnosis of neuromyelitis optica. Recognizing the distinct clinical features of this rare illness, referring specifically from a spinal cord or ophthalmological etiology, is essential for its rapid diagnosis, and hence for initiation of appropriate therapy.

Antibody to aquaporin-4 in the long-term course of neuromyelitis optica

Neuromyelitis optica (NMO) is a severe inflammatory CNS disorder of putative autoimmune aetiology, which predominantly affects the spinal cord and optic nerves. Recently, a highly specific serum reactivity to CNS microvessels, subpia and Virchow-Robin spaces was described in patients with NMO [called NMO-IgG (NMO-immunoglobulin G)]. Subsequently, aquaporin-4 (AQP4), the most abundant water channel in the CNS, was identified as its target antigen. Strong support for a pathogenic role of the antibody would come from studies demonstrating a correlation between AQP4-Ab (AQP4-antibody) titres and the clinical course of disease. In this study, we determined AQP4-Ab serum levels in 96 samples from eight NMO-IgG positive patients (median follow-up 62 months) in a newly developed fluorescence-based immunoprecipitation assay employing recombinant human AQP4. We found that AQP4-Ab serum levels correlate with clinical disease activity, with relapses being preceded by an up to 3-fold increase in AQP4-Ab titres, which was not paralleled by a rise in other serum autoantibodies in one patient. Moreover, AQP4-Ab titres were found to correlate with CD19 cell counts during therapy with rituximab. Treatment with immunosuppressants such as rituximab, azathioprine and cyclophosphamide resulted in a marked reduction in antibody levels and relapse rates. Our results demonstrate a strong relationship between AQP4-Abs and clinical state, and support the hypothesis that these antibodies are involved in the pathogenesis of NMO.

Neuromyelitis optica: a distinct demyelinating disease of the central nervous system

OBJECTIVES

We review and discuss the pathogenesis, epidemiology, diagnosis as well as recent advances in the treatment of NMO. We also highlight areas of future research.

METHODS

A review was carried out on reports drawn from MEDLINE until 2007.

RESULTS

Neuromyelitis optica (NMO) is a relative uncommon demyelinating disease of the central nervous system (CNS) that preferentially affects the optic nerves and spinal cord. NMO follows an unpredictable course, being either monophasic or relapsing. The relapsing form of NMO primarily affects women with onset varying from childhood to adults in their 40s or elderly. Until recently, NMO was considered to be a variant of multiple sclerosis. However, in contrast to multiple sclerosis, NMO attacks are not mediated by T cells but rather by B cells and NMO-immunoglobulin G antibodies that target aquaporin-4. Humoral immune mechanisms, including complement activation plays an important role in the pathogenesis of NMO. At present, parenteral corticosteroids are widely employed as first-line treatment of optic neuritis and myelitis attacks, whereas therapeutic plasmapheresis is applied in the case of corticosteroids failure. Various strategies for the prevention of NMO relapses have been employed in small case series with modest activity.

CONCLUSION

Recent advances in the clinical, neuroimaging, laboratory and pathological hallmarks have established that NMO is a distinct demyelinating disease of the CNS.

Differential diagnosis of suspected multiple sclerosis: a consensus approach

BACKGROUND AND OBJECTIVES

Diagnosis of multiple sclerosis (MS) requires exclusion of diseases that could better explain the clinical and paraclinical findings. A systematic process for exclusion of alternative diagnoses has not been defined. An International Panel of MS experts developed consensus perspectives on MS differential diagnosis.

METHODS

Using available literature and consensus, we developed guidelines for MS differential diagnosis, focusing on exclusion of potential MS mimics, diagnosis of common initial isolated clinical syndromes, and differentiating between MS and non-MS idiopathic inflammatory demyelinating diseases.

RESULTS

We present recommendations for 1) clinical and paraclinical red flags suggesting alternative diagnoses to MS; 2) more precise definition of "clinically isolated syndromes" (CIS), often the first presentations of MS or its alternatives; 3) algorithms for diagnosis of three common CISs related to MS in the optic nerves, brainstem, and spinal cord; and 4) a classification scheme and diagnosis criteria for idiopathic inflammatory demyelinating disorders of the central nervous system.

CONCLUSIONS

Differential diagnosis leading to MS or alternatives is complex and a strong evidence base is lacking. Consensus-determined guidelines provide a practical path for diagnosis and will be useful for the non-MS specialist neurologist. Recommendations are made for future research to validate and support these guidelines. Guidance on the differential diagnosis process when MS is under consideration will enhance diagnostic accuracy and precision.

NMO-IgG positive neuromyelitis optica in a patient with myasthenia gravis but no thymectomy

Here we report on a 44-year old woman presenting with both myasthenia gravis (MG) and neuromyelitis optica (NMO). MRI showed transverse myelitis extending from C2 to T4, multifocal demyelinating lesions in the supratentorial white matter, and left optic neuritis. Serological analysis demonstrated antibodies to acetylcholine receptors as well as NMO-IgG. To our knowledge, this is the first case of NMO-IgG positive NMO in a patient with MG but no history of thymectomy or immunosuppression.

Seroprevalence of NMO-IgG antibody in Brazilian patients with neuromyelitis optica

OBJECTIVE: To determine the seroprevalence of neuromyelitis optica antibody (NMO)-IgG in Brazilian patients with clinical diagnosis of relapsing neuromyelitis optica, also known as Devic's disease. METHOD: We determined NMO-IgG titers in 28 patients (25 of them females) that fulfilled the 1999 NMO diagnostic criteria proposed by Wingerchuk et al. RESULTS: NMO-IgG was detected in 18 NMO patients (64.3%). CONCLUSION: Our results showed that seroprevalence of NMO-IgG in Brazilian NMO patients was similar to the observed in other studies.

Mechanisms of disease: aquaporin-4 antibodies in neuromyelitis optica

Neuromyelitis optica (NMO) is a rare CNS inflammatory disorder that predominantly affects the optic nerves and spinal cord. Recent serological findings strongly suggest that NMO is a distinct disease rather than a subtype of multiple sclerosis. In NMO, serum antibodies, collectively known as NMO-IgG, characteristically bind to cerebral microvessels, pia mater and Virchow-Robin spaces. The main target antigen for this immunoreactivity has been identified as aquaporin-4 (AQP4). The antibodies are highly specific for NMO, and they are also found in patients with longitudinally extensive transverse myelitis without optic neuritis, which is thought to be a precursor to NMO in some cases. An antibody-mediated pathogenesis for NMO is supported by several observations, including the characteristics of the AQP4 antibodies, the distinct NMO pathology--which includes IgG and complement deposition and loss of AQP4 from spinal cord lesions--and emerging evidence of the beneficial effects of B-cell depletion and plasma exchange. Many aspects of the pathogenesis, however, remain unclear.

[Neuromyelitis optica]

Neuromyelitis optica (NMO, Devic syndrome) is a rare demyelinating disease of the central nervous system which mostly follows a relapsing course. Key features of this disorder include unilateral or bilateral optic neuritis and longitudinally extensive myelitis (> or = three segments). Brain lesions are rarely present at onset. They may however evolve during the course of disease but usually remain asymptomatic. The histopathology of NMO is suggestive of an underlying humoral autoimmune pathomechanism and indicates that NMO is a distinct entity rather than a variant of multiple sclerosis. The recent detection of NMO-specific serum autoantibodies against the water channel aquaporin-4 (Aqp4) is of significant diagnostic relevance and classifies NMO as the first inflammatory demyelinating disorder of the CNS with a defined autoantigen. More recent therapeutic strategies such as plasma exchange or pharmacological B-cell depletion are expected to improve long-term prognosis of NMO.

Neuromyelitis optica spectrum disorder in a patient with systemic lupus erythematosus and anti-phospholipid antibody syndrome

Neuromyelitis optica (NMO) is a demyelinating disease of the central nervous system characterized by severe episodes of optic nerve and spinal cord inflammation. NMO-IgG (anti-aquaporin-4) has been recently described as a sensitive and specific marker for NMO. As there have been prior published reports of an association between NMO and systemic autoimmune diseases, the prognostic value of the antibody test in these cases is uncertain. We describe a 47-year old woman with recurrent transverse myelitis and a long-standing history of systemic lupus erythematosus (SLE) and antiphospholipid antibody syndrome (APLS). While she did not have a history of optic neuritis, serological testing for the NMO-IgG was positive when she was admitted for her second episode of transverse myelitis. Testing for the NMO-IgG in cases of isolated or recurrent transverse myelitis attributed to current SLE and APLS may help clarify the diagnosis of a distinct disease process likely to cause recurrent and severe disability, warranting more aggressive immunotherapy.

NMO-IgG and Devic's neuromyelitis optica: a French experience

Background A serum autoantibody biomarker, NMO-IgG has been recently described in patients with Devic's neuromyelitis optica (DNMO) and so called `high-risk' patients for this disease. Our objectives were to replicate the test and to assess its usefulness.

Methods Indirect immunofluorescence with a substrate of adult rat cerebellum and midbrain was used to identify the distinctive NMO-IgG staining pattern. We tested masked sera from 26 patients with DNMO (group 1), 21 patients with idiopathic acute transverse myelitis (ATM) (group 2), 21 patients with bilateral and/or recurrent idiopathic optic neuritis (group 3), 52 patients with classical multiple sclerosis (MS) (group 4), 36 patients with HTLV-1 infection (group 5) and 7 patients with miscellaneous disorders (group 6).

Results We identified a vascular staining pattern typical of NMO-IgG. This particular staining was observed in 14/26 samples in group 1, 7/21 in group 2 (positive only in longitudinally extensive acute transverse myelitis: 7/13), 4/21 in group 3 (with bilateral loss of vision in all seropositive cases), 5/52 in group 4 (none of them suggestive of DNMO), 0/36 in group 5 and 0/7 in group 6. Sensitivity of the test was 54% considering detection of DNMO (group 1), and specificity was respectively 94% and 90% when considering groups 4, 5 and 6 altogether or group 4 of MS patients only.

Conclusion Detection of NMO-IgG is contributory to the distinction of DNMO and `DNMO high-risk' syndromes from MS. This test may allow earlier diagnosis and help therapeutic decisions. Multiple Sclerosis 2008; 14: 440—445. http://msj.sagepub.com

Neuromyelitis optica in a patient with an early onset demyelinating episode: clinical and autoantibody findings

Recent clinical and laboratory findings have substantially advanced our understanding of neuromyelitis optica (NMO) as a humorally mediated, autoimmune disorder. We report on a patient who suffered a first episode of transverse myelitis at the age of 6 months following diphtheria-pertussis-tetanus (DPT) vaccination which had therefore been considered suggestive of acute disseminated encephalomyelitis (ADEM). Fifteen years later, the further disease course revealed typical NMO meeting all diagnostic criteria. This development points to a broad clinical and temporal heterogeneity of NMO, with ADEM probably occurring in the context of a shared autoimmune diathesis. Despite therapy response following B-cell depletion by rituximab, positive NMO-IgG autoantibody status remained unchanged, whereas direct testing for anti-aquaporin-4 (AQP-4)-antibodies was negative throughout. Our findings challenge the pathogenic relevance of NMO-IgG and indicate a varying diagnostic value of testing for NMO-IgG and AQP-4-autoantibodies.

Neuromyelitis optica: clinical syndrome and the NMO-IgG autoantibody marker

Neuromyelitis optica (NMO) is a severe demyelinating disease of the CNS that preferentially affects the optic nerves and spinal cord, tends to relapse, and results in early permanent disability for most affected patients. A new autoantibody marker called neuromyelitis optica immunoglobulin G (NMO-IgG), which targets the water channel protein aquaporin-4, is highly specific for NMO. The marker has demonstrated that the NMO spectrum of disorders is wider than previously known and includes some patients with single-episode or recurrent longitudinally extensive myelitis, recurrent isolated optic neuritis, Asian optic-spinal multiple sclerosis, and patients with co-existing systemic autoimmune diseases such as lupus erythematosus or Sjögren's syndrome. We review the place of NMO within the nosology of CNS demyelinating diseases, the discovery of NMO-IgG and its impact on the definition of NMO and its spectrum, implications for understanding NMO pathogenesis, and informing treatment decisions.

The spectrum of neuromyelitis optica

Neuromyelitis optica (also known as Devic's disease) is an idiopathic, severe, demyelinating disease of the central nervous system that preferentially affects the optic nerve and spinal cord. Neuromyelitis optica has a worldwide distribution, poor prognosis, and has long been thought of as a variant of multiple sclerosis; however, clinical, laboratory, immunological, and pathological characteristics that distinguish it from multiple sclerosis are now recognised. The presence of a highly specific serum autoantibody marker (NMO-IgG) further differentiates neuromyelitis optica from multiple sclerosis and has helped to define a neuromyelitis optica spectrum of disorders. NMO-IgG reacts with the water channel aquaporin 4. Data suggest that autoantibodies to aquaporin 4 derived from peripheral B cells cause the activation of complement, inflammatory demyelination, and necrosis that is seen in neuromyelitis optica. The knowledge gained from further assessment of the exact role of NMO-IgG in the pathogenesis of neuromyelitis optica will provide a foundation for rational therapeutic trials for this rapidly disabling disease.

Neuromyelitis optica: Changing concepts

Neuromyelitis optica (NMO; Devic's disease) and the NMO spectrum disorders are idiopathic inflammatory demyelinating disorders that affect the central nervous system and have a predilection for optic nerves and spinal cord. The identification of NMO-IgG as a disease-specific marker and aquaporin 4 as the target antigen has renewed interest in NMO. Based on current data, we suspect that autoantibodies arising from peripheral B cells bind to aquaporin 4 expressed on astrocyte foot processes on the abluminal surface of microvessels, activate complement and initiate inflammatory demyelination and necrosis. The development of animal models and further analysis of the association of NMO-IgG with disease severity and treatment response will elucidate the pathobiology of NMO.