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Introduction: In this study we describe the clinical and molecular characteristics of limb-girdle muscular dystrophy (LGMD) due to LAMA2 mutations. Methods: Five patients clinically diagnosed with LGMD and showing brain white matter hyperintensities on MRI were evaluated using laminin α2 genetic and protein testing. Results: The patients had slowly progressive, mild muscular dystrophy with various degrees of CNS involvement. Epilepsy was observed in 2, and subtle symptoms of CNS involvement (mild deficit in executive functions and low IQ scores) were noted in 3 patients. Novel LAMA2 mutations were identified in all patients. The amount of laminin α2 protein in the muscle biopsies ranged from trace to about 50% compared with controls. Conclusions: This study represents the largest series of LGMD laminin α2–deficient patients and expands the clinical phenotype associated with LAMA2 mutations. The findings suggest that brain MRI could be included in the diagnostic work-up of patients with undiagnosed LGMD. Muscle Nerve, 2011

Studies of twins, adoptees, half siblings, and familial recurrence risk have shown that genetic and non-genetic factors are involved in multiple sclerosis (MS) etiology. Age at onset, gender, and parental MS status seem to influence sibling risk. We studied the recurrence risk in siblings of MS patients in an isolated population of Sardinia, Italy, which is genetically homogeneous, inbred, and very stable, with a high MS frequency. The Aalen-Nelson estimate of the recurrence risk in siblings is 4.7%, and the risk ratio compared with the general population is 31. Proportional hazards models were used to investigate the effect of sibling sex, sex, and age at onset of the proband, and number of affected relatives on a sibling's predicted MS risk. Sib's risk is influenced by age at onset (P = 0.02), and possibly by sex of the proband (P = 0.08). There is also a borderline significant interaction (P = 0.05) between the sex and age at onset of the proband: early age at onset influences sib's risk only if the proband is female. The number of affected relatives in the family is not found to influence sibling risk, but the power is lacking (95% CI 0.50-2.62). This result is consistent with a single dominant gene with an extremely low penetrance, a model that has not yet been disproved as a possible inheritance model for MS.

Association and linkage studies have established the importance of the major histocompatibility complex (MHC) in the susceptibility for multiple sclerosis (MS). We carried out a case-control study to investigate the ancestral haplotype A30B18DR3 and MS in the Nuoro population of Sardinia, which is isolated and genetically distinct from other populations in the Mediterranean basin and characterized by genetic homogeneity, high level of inbreeding, low migration, high prevalence of MS, high frequency of the relevant haplotype, and high past malaria prevalence. Cases and controls were serologically typed for the currently recognized HLA-A, B, and DR antigens. We used a log-linear approach to fit a wide class of models. We tested our hypothesis comparing different models via a likelihood ratio test. We overcame the complication due to unknown gametic phase using expectation-maximization (EM) algorithm as the estimation method. We estimated confidence intervals for odds ratio by using a profile likelihood approach. We found that: (1) the ancestral haplotype A30B18DR3 was associated to MS after allowing for a possible stratification in cases and controls; (2) DR3 allele was conditional independent on disease status, given A30B18 haplotype; (3) there was a tendency for ORs for the high-risk haplotypes to be higher in the high malaria strata; however, this indication did not achieve statistical significance (P = 0.11).