Myasthenia gravis patients with anti-MuSK antibodies.

In myasthenia gravis (MG) patients without detectable anti-acetylcholine receptor (anti-AChR) antibody, referred to as seronegative myasthenia gravis patients, there is a variable proportion of patients with antibodies against the muscle-specific kinase (MuSK). MuSK antibodies were found in 8 (29.6%) of our 27 patients with generalized MG without anti-AChR antibodies. All these patients were female. The age at the onset ranged from 22 to 38 years. All patients had ocular and bulbar symptoms, and two patients also had generalized limb weakness. Two patients had pure ocular symptoms for 7 or 8 years before the development of bulbar symptoms. All anti-MuSK positive patients were treated with immunosuppressive drugs, three received plasmapheresis and one patient required mechanical ventilation. Our results are consistent with other literature reports.

Apolipoprotein H (apoH)-dependent autoantibodies and apoH protein polymorphism in selected patients showing lupus anticoagulant activity.

Apolipoprotein H (apoH) is considered to be a necessary cofactor for the binding of certain antiphospholipid antibodies to anionic phospholipids. Some apoH-dependent antiphospholipid antibodies also exert lupus anticoagulant (LA) activity, which seems to depend on antiphospholipid antibody epitope specificity. The aim of this study was to evaluate whether the presence of less frequent apoH alleles may induce structural or conformational changes in these "LA-dependent" regions that may initiate more frequent autoimmune responses in subjects. We selected patients with confirmed LA activity and none or low titers of anticardiolipin antibodies that had been sent to the laboratory for routine antiphospholipid antibody determination. Many of them had some clinical manifestation of antiphospholipid syndrome. Antibodies to apoH were determined with a commercially available anticardiolipin/apoH ELISA kit. ApoH protein polymorphism (apoH phenotype) was demonstrated by isoelectric focusing and immunoblotting. Our results showed that 47/74 (63.5%) of our selected LA-positive patients also had elevated apoH-dependent antiphospholipid antibody titers. These results point to two subgroups of patients according to the LA potency of apoH-dependent antibodies. A strong positive correlation (non-linear or linear) for apoH-dependent antibody titers and LA activity was observed in both subgroups of patients. In this study, we did not find significant differences in the distribution of apoH phenotypes among control subjects and patients with apoH-dependent/LA-positive auto- antibodies.

Apolipoprotein H genetic variability in the population of Krk Island, Croatia.

Apolipoprotein polymorphisms are emerging as suitable markers for the study of the formation of human populations. In contrast to the data available for apolipoprotein E, the data regarding apolipoprotein H (protein, apoH; gene, APOH) variations are only beginning to accumulate. By blood plasma isoelectric focusing and immunoblotting, we analyzed the distribution of apoH phenotypes in 397 individuals (192 males; 205 females) from seven villages of an autochthonous population of the eastern Adriatic island of Krk. APOH allele frequencies were: APOH*2 = 0.877, APOH*3 = 0.098, APOH*1 = 0.025, with the majority of the sample being homozygous. No significant differences between villages were observed. When these data were compared to those of other populations studied so far, a significant association between APOH allele frequencies and latitude was observed. We hypothesize that this association reflects differences in diet composition across different climatic zones.