I. Illa

Investigations of Caspr2, an autoantigen of encephalitis and neuromyotonia

To report clinical and immunological investigations of contactin‐associated protein‐like 2 (Caspr2), an autoantigen of encephalitis and peripheral nerve hyperexcitability (PNH) previously attributed to voltage‐gated potassium channels (VGKC).

Inflammation in dysferlin myopathy: immunohistochemical characterization of 13 patients.

Inflammation was detected in 9 of 13 patients with different phenotypes of dysferlin myopathy. Endomysial or perivascular infiltrates consisted of 11.1% ± 6.6% CD8+ cells, 40.6% ± 22.8% CD4+ cells, 36.7% ± 23.7% macrophages, and no B cells. Major histocompatibility complex class I was not upregulated in normal muscle fibers. In young patients with sporadic proximal weakness, very high creatine kinase levels, necrotic fibers and inflammation in the muscle biopsy, a diagnosis of dysferlin myopathy should be considered.

Long-lasting treatment effect of rituximab in MuSK myasthenia.

Objective: Rituximab has emerged as an efficacious option for drug-resistant myasthenia gravis (MG). However, reports published only describe the short-term follow-up of patients treated and little is known about their long-term clinical and immunologic evolution. Our objective was to report the clinical and immunologic long-term follow-up of 17 patients (6 MuSK+MG and 11 AChR+MG) and compare the response between AChR+MG and MuSK+MG patients. Methods: Myasthenia Gravis Foundation America postintervention status and changes in treatment and antibody titers were periodically determined. Lymphocyte subpopulations, total immunoglobulin, immunoglobulin G (IgG) anti-MuSK subclasses, and anti-tetanus toxoid IgG before and after treatment were also studied. Results: After a mean post-treatment period of 31 months, 10 of the AChR+MG patients improved but 6 of them needed reinfusions. In contrast, all MuSK+MG patients achieved a remission (4/6) or minimal manifestations (2/6) status and no reinfusions were needed. Consequently, in the MuSK+MG group, prednisone doses were significantly reduced and concomitant immunosuppressants could be withdrawn. Clinical improvement was associated with a significant decrease in the antibody titers only in the 6 MuSK+MG patients. At last follow-up MuSK antibodies were negative in 3 of these patients and showed a decrease of over 80% in the other 3. Conclusion: In view of the long-lasting benefit observed in MuSK+MG patients, we recommend to use rituximab as an early therapeutic option in this group of patients with MG if they do not respond to prednisone. Classification of evidence: This study provides Class IV evidence that IV rituximab improves the clinical and immunologic status of patients with MuSK+MG.

Effect of intraventricular injection of an anti-Purkinje cell antibody (anti-Yo) in a guinea pig model

Female guinea pigs had intraventricular injections of either IgG from a patient with paraneoplastic cerebellar degeneration (PCD) and anti-Purkinje cell antibodies (anti-Yo IgG) or control IgG. In animals that received a single injection of control or anti-Yo IgG and were killed at different time intervals, IgG immunoreactivity was present in the cytoplasm of Purkinje cells at 2 h and persisted at 24 h. In guinea pigs injected for 15 days with control or anti-Yo IgG and sacrificed 24 h after the last injection, IgG was detected into the Purkinje cells in both groups, whereas animals killed 7 and 30 days after the last injection had no staining for IgG in the Purkinje cells. Clinical or pathologic evidence of cerebellar involvement was not seen in any of the animals. This study suggests that anti-Yo antibody alone may not be the cause of the Purkinje cell loss in PCD.

Chronic neuropathy with IgM anti-ganglioside antibodies: Lack of long term response to rituximab

Two patients with chronic motor neuropathy, high antiganglioside antibody (AGA) titers, and a declining response to IV immunoglobulins were treated with rituximab at a standard dose. The drug was well tolerated and effectively eliminated peripheral B cells (CD20+), but AGA titers continued significantly high. No clinical improvement was detected during the 1-year follow-up.

Redefining dysferlinopathy phenotypes based on clinical findings and muscle imaging studies

Background: The most frequent phenotypes of dysferlin myopathy are limb-girdle muscular dystrophy 2B (LGMD2B) and Miyoshi myopathy (MM). Our objective was to find clinical or MRI markers to differentiate phenotypes of dysferlin myopathy regardless of initial symptoms. Methods: This retrospective study included 29 patients with confirmed mutations in the DYSF gene (14 MM, 12 LGMD2B, 1 asymptomatic hyperCKemia, and 2 symptomatic carriers). All underwent an annual clinical examination (Medical Research Council scale), functional status assessment, and creatine kinase, pulmonary, and cardiac testing. For research purposes, we performed lower limb MRI studies in all 29 patients to identify the pattern of muscle impairment and to quantify involvement. Statistical correlations between MRI findings and phenotype, disease duration, and functional status were determined. Results: The mean clinical follow-up was 6.4 ± 5.7 years. No significant differences were found in the rate of progression, functional prognosis, or mutations between patients with MM and patients with LGMD2B. The MRI pattern of muscle involvement was the same for patients with MM and patients with LGMD2B. The adductor magnus and gastrocnemius medialis were the first to be impaired in both phenotypes. The progression of muscle involvement correlated with clinical status. Conclusions: Splitting dysferlin myopathy into separate phenotypes does not reveal significant differences in terms of rate of progression, prognosis, genotype, or MRI pattern. The finding that proximal and distal muscles are already impaired in the MRI at onset in both MM and LGMD2B favors grouping all phenotypes under the term dysferlin myopathy.

Dysferlin expression in monocytes: A source of mRNA for mutation analysis

Dysferlin protein is expressed in peripheral blood monocytes. The genomic analysis of the DYSF gene has proved to be time consuming because it has 55 exons. We designed a mutational screening strategy based on cDNA from monocytes to find out whether the mutational analysis could be performed in mRNA from a source less invasive than the muscle biopsy. We studied 34 patients from 23 families diagnosed with dysferlinopathy. The diagnosis was based on clinical findings and on the absence of protein expression using either immunohistochemistry or Western blot of skeletal muscle and/or monocytes. We identified 28 different mutations, 13 of which were novel. The DYSF mutations in both alleles were found in 30 patients and only in one allele in four. The results were confirmed using genomic DNA in 26/34 patients. This is the first report to furnish evidence of reliable mutational analysis using monocytes cDNA and constitutes a good alternative to genomic DNA analysis.

The expanding field of IgG4-mediated neurological autoimmune disorders

At least 13 different disease entities affecting the central nervous system, peripheral nervous system and connective tissue of the skin or kidneys are associated with immunoglobulin G4 (IgG4) immune reactivity. IgG4 has always been considered a benign, non‐inflammatory subclass of IgG, in contrast to the well‐known complement‐activating pro‐inflammatory IgG1 subclass. A comprehensive review of these IgG4 autoimmune disorders reveals striking similarities in epitope binding and human leukocyte antigen (HLA) associations. Mechanical interference of extracellular ligand−receptor interactions by the associated IgG4 antibodies seems to be the common/converging disease mechanism in these disorders.

Symptomatic dysferlin gene mutation carriers: Characterization of two cases

Objective: To describe two symptomatic dysferlin gene mutation carriers. Methods: One patient had limb girdle weakness. His brother was diagnosed with limb girdle muscular dystrophy 2B with two mutations in the dysferlin gene (D625Y and E1734G). The second patient had distal weakness. He had two sons with Miyoshi myopathy with a homozygous mutation (G519R). We performed immunofluorescence (dystrophin, DAG proteins, dysferlin, caveolin-3), Western blot (dysferlin, caveolin-3, calpain-3), and real-time PCR (dysferlin) using skeletal muscle samples. We also studied dysferlin in peripheral blood monocytes (PBMs) by Western blot. Results: In addition to the muscle weakness, both patients showed elevated creatine kinase and abnormal muscle MRI. They presented a mutation in only one allele after screening of the whole gene (skeletal muscle and monocyte mRNA and genomic DNA). A muscle biopsy specimen showed moderate dystrophic changes and patchy dysferlin expression in the sarcolemma. Western blot of both PBMs and skeletal muscle demonstrated a significant reduction in dysferlin. All the other proteins including caveolin-3 and calpain-3 were normal. Real-time PCR showed normal levels of dysferlin mRNA vs the patients affected relatives. Conclusions: The diagnosis of symptomatic carriers of dysferlin mutations should be considered when a pathologic pattern of dysferlin protein is observed.

Antiganglioside antibodies in acute self-limiting ataxic neuropathy: incidence and significance

Antidisialosyl antibodies have been previously associated to chronic and acute ataxic neuropathies. We studied the presence of these antibodies in nine patients with acute self-limiting ataxic neuropathy (ASLAN) using ELISA and TLC immunodetection. One patient showed serum IgG immunoreactivity against gangliosides GD3 and GQ1b. The patients IgG was able to bind to the nodes of Ranvier on frozen human dorsal root. Our studies confirmed that antidisialosyl reactivity is associated to ataxic neuropathy and its specific binding to the dorsal root could explain the predominant sensory involvement. Nevertheless, the low incidence of this reactivity indicates that a different pathogenic mechanism should be involved in most ASLAN patients.