W.L. van der Pol

Relevance of Fcγ Receptor and Interleukin-10 Polymorphisms for Meningococcal Disease

The contribution of individual Fcgamma receptor (FcgammaR) subclasses to meningococcal phagocytosis was studied. In addition, functional FcgammaR polymorphisms were determined in 50 patients with meningococcal disease (MD), in 183 first-degree relatives of MD patients, and in 239 healthy control subjects, to study the association of FcgammaR genotypes with disease. Efficient internalization of opsonized Neisseria meningitidis serogroup B was mediated via multiple FcgammaR subclasses on phagocytes. Accordingly, a low-efficiency combination of FcgammaRIIa-R/R131, FcgammaRIIIa-F/F158, and FcgammaRIIIb-NA2/2 genotypes was increased significantly in relatives of patients with MD, compared with healthy control subjects (P<.05; odds ratio, 2.6; 95% confidence interval, 1.1-6.3). FcgammaRIIa and FcgammaRIIIa genotype distributions differed between patients with sepsis and those with meningitis. Combined genotypes of FcgammaRIIa and interleukin-10 -1082, which was previously reported as being associated with MD outcome, were distributed randomly in control subjects but not in relatives of patients with MD (P<.01). These data provide further evidence for the association of polymorphic genes on chromosome 1 and MD.

Activity of Human IgG and IgA Subclasses in Immune Defense Against Neisseria meningitidis Serogroup B

Both IgG and IgA Abs have been implicated in host defense against bacterial infections, although their relative contributions remain unclear. We generated a unique panel of human chimeric Abs of all human IgG and IgA subclasses with identical V genes against porin A, a major subcapsular protein Ag of Neisseria meningitidis and a vaccine candidate. Chimeric Abs were produced in baby hamster kidney cells, and IgA-producing clones were cotransfected with human J chain and/or human secretory component. Although IgG (isotypes IgG1–3) mediated efficient complement-dependent lysis, IgA was unable to. However, IgA proved equally active to IgG in stimulating polymorphonuclear leukocyte respiratory burst. Remarkably, although porin-specific monomeric, dimeric, and polymeric IgA triggered efficient phagocytosis, secretory IgA did not. These studies reveal unique and nonoverlapping roles for IgG and IgA Abs in defense against meningococcal infections.

Correlates of outcome and response to IVIg in 88 patients with multifocal motor neuropathy

Reply from the Authors: We thank Dr. Nabbout et al. for their comments on our article, in which we described 13 probands, and one of their mothers, with epilepsy variably associated with mental retardation and autistic features in whom the PCDH19 gene was mutated.1 The epilepsy phenotype was variable. Seven patients exhibited DS and 6 had focal epilepsy. These figures confirm that PCDH19 mutations can cause an epileptic encephalopathy resembling DS in girls.2 Therefore, if screening for SCN1A gene mutations, deletions, amplification, or duplications yields negative results, PCDH19 should be screened. In our cohort, girls with PCDH19 mutations and focal epilepsy had early seizure onset and either normal cognitive skills or mental retardation and autistic features. The spectrum of phenotypes associated with PCDH19 mutations is broad, ranging from mild epilepsy to a severe epileptic encephalopathy. Such phenotypic diversity might be partially explained by the cosegregation of other genetic factors either rescuing or worsening the phenotype. Since our article was accepted for publication, we have observed 6 more girls with PCDH19 mutations, none having a phenotype evocative of DS (unpublished data). Another article reported 3 girls with seizure onset in infancy and varying degrees of cognitive impairment and autistic features.3 However, the core clinical features of PCDH19-related epilepsy phenotypes seem to be early onset of seizures occurring in clusters and precipitated by fever. The spectrum of associated cognitive and behavioral impairment is variable and its relationship with epilepsy severity is not obvious. PCDH19 is clearly emerging as a major epilepsy gene in females. Analysis of larger cohorts, with unbiased recruitment, will clarify the full range of phenotypes caused by alterations in this gene.

Multifocal motor neuropathy Association of anti-GM1 IgM antibodies with clinical features

Objective: To determine the prevalence and specificity of antibodies against single gangliosides and ganglioside complexes in serum from 88 patients with multifocal motor neuropathy (MMN) and to study the association with clinical features. Methods: ELISA was used to detect immunoglobulin (Ig)M, IgG, and IgA antibodies against GM1, GM2, GD1a, GD1b, GM1b, GT1a, GT1b, GQ1b, GalNAc-GD1a, and the glycolipid SGPG; absorption studies were performed to study cross-reactivity. Presence of antibodies against ganglioside complexes consisting of any of combinations of GM1, GM2, GD1a, GD1b, GT1b, and GQ1b was also tested. Results: Anti-GM1 IgM, IgG, and IgA antibodies were detected in serum from 43%, 1%, and 5% of patients with MMN. Anti-GM2 IgM antibodies were detected in 6% and anti-GD1b IgM antibodies in 9% of patients. Patients with MMN with anti-GM1 IgM antibodies had more severe weakness (p < 0.01), more disability (p < 0.01), and more axon loss (p = 0.05) than patients without anti-GM1 IgM antibodies. Anti-GM1 IgM antibody titers correlated with Medical Research Council scores (correlation coefficient = 0.43; p < 0.0001). Anti-GD1b IgM antibody activity was associated with reduced vibration sense (p < 0.01). Absorption studies showed that anti-GD1b and anti-GM2 IgM antibodies cross-reacted with GM1. Antibodies against ganglioside complexes were not detected. Complexes containing GD1a, GD1b, GT1b, or GQ1b with GM1 lowered antibody activity against GM1. Conclusion: Anti-ganglioside IgM antibodies in MMN display limited specificity and are associated with severity and clinical characteristics. Results of this study suggest that anti-GM1 IgM antibodies may play a role in MMN pathogenesis.

The Lambert–Eaton myasthenic syndrome 1988–2008: A clinical picture in 97 patients

BACKGROUND Neuromuscular symptoms in patients with Lambert-Eaton myasthenic syndrome (LEMS) and a small cell lung cancer (SCLC) develop more rapidly than in LEMS patients without a SCLC. We studied how this clinical information, which is readily available at the first consultation, can be used to predict the presence of SCLC. PATIENTS AND METHODS In our study we included 52 LEMS patients with SCLC and 45 non-tumor patients (NT-LEMS). We interviewed patients using a structured checklist and reviewed their clinical records. We compared frequency and onset of symptoms during the course of LEMS. RESULTS In the first six months, over half the SCLC-LEMS patients had developed seven separate symptoms, while NT-LEMS patients developed only two symptoms. Proximal leg weakness and dry mouth were early symptoms in both groups. Rapid involvement of proximal arm muscles (p=0.0001), distal arm muscles (p=0.0037), distal leg muscles (p=0.0002), dysartria (p=0.0091) and the presence of erectile dysfunction (p=0.007) were found significantly more often in SCLC-LEMS patients in both cohorts. Cerebellar symptoms, although present in 9% of LEMS patients, were almost exclusively related to SCLC-LEMS. CONCLUSION A rapidly progressive course of disease from onset in LEMS patients should raise a high suspicion of SCLC. Special attention should be paid to involvement of upper extremities, involvement of distal arm and distal leg muscles, to erectile dysfunction and probably ataxia in order to discriminate between SCLC-LEMS and NT-LEMS.

Mutations in RYR1 are a common cause of exertional myalgia and rhabdomyolysis

Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are a common cause of neuromuscular disease, ranging from various congenital myopathies to the malignant hyperthermia (MH) susceptibility trait without associated weakness. We sequenced RYR1 in 39 unrelated families with rhabdomyolysis and/or exertional myalgia, frequent presentations in the neuromuscular clinic that often remain unexplained despite extensive investigations. We identified 9 heterozygous RYR1 mutations/variants in 14 families, 5 of them (p.Lys1393Arg; p.Gly2434Arg; p.Thr4288_Ala4290dup; p.Ala4295Val; and p.Arg4737Gln) previously associated with MH. Index cases presented from 3 to 45 years with rhabdomyolysis, with or without exertional myalgia (n=12), or isolated exertional myalgia (n=2). Rhabdomyolysis was commonly triggered by exercise and heat and, less frequently, viral infections, alcohol and drugs. Most cases were normally strong and had no personal MH history. Inconsistent additional features included heat intolerance, and cold-induced muscle stiffness. Muscle biopsies showed mainly subtle changes. Familial RYR1 mutations were confirmed in relatives with similar or no symptoms. These findings suggest that RYR1 mutations may account for a substantial proportion of patients presenting with unexplained rhabdomyolysis and/or exertional myalgia. Associated clinico-pathological features may be subtle and require a high degree of suspicion. Additional family studies are paramount in order to identify potentially MH susceptible relatives.

IgG receptor IIa alleles determine susceptibility and severity of Guillain-Barré syndrome

Objective: Guillain-Barré syndrome (GBS) is characterized by nerve infiltration of leukocytes and autoantibodies of the immunoglobulin G (IgG) isotype directed against nerve constituents. Leukocyte receptors for IgG (FcγR) constitute an important link between the humoral and cellular parts of the immune system and confer potent cellular effector functions to myelin-directed antibodies. Three FcγR subclasses exhibit genetically determined biallelic functional polymorphisms (FcγRIIa: R131 versus H131; FcγRIIIa: 158V versus 158F; FcγRIIIb: NA1 versus NA2) that determine efficacy of the cellular immune response. To study the relevance of these polymorphisms for susceptibility and severity of GBS, we compared FcγR genotype distributions in GBS patients with those in controls. Methods: Genomic DNA was isolated from whole blood of 31 randomly selected patients with GBS and 187 healthy blood donors. Genotypes of the three polymorphic FcγR genes were determined by PCR. Results: FcγRIIa-H131 homozygosity was significantly increased in patients as compared with healthy controls (OR 2.45; 95% CI 1.12 to 5.36; p = 0.037). Furthermore, FcγRIIa-H131 homozygous GBS patients had a higher risk for severe disease than did patients with other genotypes (OR 18.57; 95% CI 1.95 to 176.49; p = 0.007). Conclusion: FcγRIIa allotypes capable of initiating efficient cellular effector functions are associated with increased risk for GBS and a more severe disease course. FcγR alleles may constitute novel genetic risk markers for GBS.

Oral dexamethasone pulse therapy versus daily prednisolone in sub-acute onset myositis, a randomised clinical trial.

To determine if high-dose pulsed dexamethasone is more effective and safer than daily high-dose prednisolone in treatment-naive adult patients with inflammatory myopathies (sporadic inclusion body myositis excluded) we performed a multicenter, double-blind randomised controlled clinical trial with 18 months follow-up. Sixty-two patients were randomised into 28-day cycles of oral high-dose dexamethasone or daily high-dose prednisolone. Primary outcome measures included (1) seven point composite score of six clinically relevant outcomes and (2) (time-to) remission and (time-to) relapse. No difference between both treatment groups on the composite score was found. Side-effects occurred significantly less frequently in the dexamethasone group. Median time to relapse was 60 (2.9) weeks in the prednisolone and 44 (4.7) weeks in the dexamethasone group (log-rank test p=0.03). In conclusion, pulsed high-dose oral dexamethasone is not superior to daily prednisolone as first-line treatment of idiopathic inflammatory myopathies, but is a good alternative by causing substantially fewer side-effects.

A natural history study of late onset spinal muscular atrophy types 3b and 4.

BackgroundSpinal muscular atrophy (SMA) is caused by a homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene plays a disease modifying role. SMA is classified into four different subtypes based on age of onset and clinical course (SMA types 1–4). The natural history of early onset SMA types 1–3a has been studied extensively. Late onset SMA is rare and disease course has not been studied in detail.ObjectiveTo perform a prospective study on the clinical course and the correlation with SMN2 copy numbers of late onset SMA.MethodsPatients fulfilling the diagnostic criteria for late onset SMA (types 3b and 4) were included in the study. At inclusion and follow-up, muscle strength, respiratory function, functional status and quality of life were assessed. SMN2 copy number was determined in all patients.ResultsTwelve patients were identified and included. Six patients were siblings from one family, two patients were brothers from a second family and four patients were sporadic cases. All patients carried four copies of the SMN2 gene. Median age of disease onset was 22.2 years (10–37). Age of disease onset in patients from family one was lower as compared to the other patients. None of the outcome measures changed after a follow-up of 2.5 years. Five patients reported an increase in fatigue and muscle weakness. None of the patients showed symptoms of respiratory insufficiency.ConclusionsThis study indicates that late onset SMA is not characterized by disease progression and that alternative or surrogate disease markers are required for the design of future trials. This study confirms the finding that SMN2 copy number is a SMA disease course modifier.

RYR1‐related myopathies: a wide spectrum of phenotypes throughout life

Although several recent studies have implicated RYR1 mutations as a common cause of various myopathies and the malignant hyperthermia susceptibility (MHS) trait, many of these studies have been limited to certain age groups, confined geographical regions or specific conditions. The aim of the present study was to investigate the full spectrum of RYR1‐related disorders throughout life and to use this knowledge to increase vigilance concerning malignant hyperthermia.