AbstractWater channels are a recognized “novel” target for central nervous system, inflammatory, autoimmune, demyelinating diseases, and represent an evolving spectrum of disorders termed neuromyelitis optica (NMO) spectrum disorders (SD). These disorders should now be considered under the umbrella term “autoimmune aquaporin‐4 channelopathy”. NMOSD represent the first multiple sclerosis (MS)‐like disease for which a specific antigen has been identified – the astrocytic water channel aquaporin‐4 (AQP4). MS lacks a distinguishing biomarker. This discovery represents a seismic shift from historic emphasis on the oligodendrocyte and myelin to the astrocyte. The NMO of today represents a relapsing spectrum of disease, not necessarily restricted to the optic nerves and spinal cord, that is different from the monophasic disorder in which near simultaneous bilateral optic neuritis and transverse myelitis occur, as was originally described by Devic. Recent clinical, radiological and pathological findings have documented brain involvement in NMO spectrum disorders, particularly in children. Most patients with NMOSD have brain abnormalities on magnetic resonance imaging, and these are consistent with MS in up to 10% of patients. Others have lesions in areas that highly express AQP4 including the circumventricular organs accounting for intractable nausea and vomiting, and the syndrome of inappropriate antidiuresis as presenting symptoms or heralds of relapse. Diencephalic involvement might explain recently recognized sleep disorders and endocrinopathies. Continued progress in our understanding of the immunobiology of AQP4 autoimmunity necessitates continuing revision of the clinical diagnostic criteria for NMO spectrum disorders. As the clinical spectrum broadens, the importance of highly specific assays that detect pathogenic AQP4‐immunoglobulin G targeting extracellular epitopes of AQP4 cannot be overemphasized.
Aquaporin 4 IgG Serostatus and Outcome in Recurrent Longitudinally Extensive Transverse Myelitis
ABSTRACTIntroductionThe clinical significance of striational antibodies (StrAbs) detected in the course of paraneoplastic antibody testing is unknown.MethodsWe compared all 203 striational antibody (StrAb)‐seropositive patients identified (2004–2005) during evaluation for paraneoplastic antibodies with age‐ and sex‐matched seronegative controls.ResultsThymoma and myasthenia gravis (MG) were significantly more common among cases (P<0.0001). Cancers more rarely detected after StrAb detection were adenocarcinoma in 5 patients and sarcoma in 3 patients. All patients who had a cancer identified after StrAb testing had a titer of ≥1:7680 or a coexisting muscle AChR‐binding antibody. Autoimmune disorders more commonly observed among cases (with any StrAb value) included: hypothyroidism; rheumatoid arthritis; and pernicious anemia (all P<0.05).ConclusionsStrAbs may serve as a diagnostic clue for an autoimmune diagnosis. There is a low likelihood of oncological significance in patients with StrAb titers <1:7680 without coexisting paraneoplastic Abs. Muscle Nerve, 2013