Reports from North America and Northern Europe have suggested that antimitochondrial antibody (AMA) negative primary biliary cirrhosis (PBC) is a distinct chronic cholestatic liver disease with high prevalence of serum non‐organ‐specific autoantibodies other than AMA. To evaluate if such a peculiar serum immunoreactivity is associated with clinically relevant characteristics, we reviewed our experience with 297 Italian patients who have had a clinical and histological diagnosis of PBC and were regularly followed‐up at our Center from June 1974 to June 1994. AMA‐negative and AMA‐positive patients were compared in terms of biochemical and clinical features, and clinical outcome of the disease. At presentation, 30 of 297 patients (10%) tested negative for AMA by indirect immunofluorescence. Six of them tested positive for antimitochondrial M2 antibodies (AMA‐M2) by immunoblotting analysis, therefore, diagnosis of AMA‐negative PBC was made in 24 patients (8%). At the initial visit, AMA‐negative and AMA‐positive patients were similar in terms of biochemical and clinical features. Antinuclear and anti‐smooth‐muscle antibodies (ANA and ASMA) were more frequently positive in the AMA‐negative patients (71% vs. 31%, and 37% vs. 9%; both P = .0002). Incidence of complications of cirrhosis and development of liver failure resulting in death or referral for liver transplantation did not differ significantly between the two populations. In conclusion, data from this historical cohort study suggest that the distinct serological features of AMA‐negative PBC are not associated with substantial differences in the clinical spectrum or course of the disease.

Abstract-Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial arrhythmogenic disorder associated with mutations in the cardiac ryanodine receptor (RyR2) and cardiac calsequestrin (CASQ2) genes. Previous in vitro studies suggested that RyR2 and CASQ2 interact as parts of a multimolecular Ca 2ϩ -signaling complex; however, direct evidence for such interactions and their potential significance to myocardial function remain to be determined. We identified a novel CASQ2 mutation in a young female with a structurally normal heart and unexplained syncopal episodes. This mutation results in the nonconservative substitution of glutamine for arginine at amino acid 33 of CASQ2 (R33Q). Adenoviral-mediated expression of CASQ2 R33Q in adult rat myocytes led to an increase in excitationcontraction coupling gain and to more frequent occurrences of spontaneous propagating (

Background— Four distinct mutations in the human cardiac calsequestrin gene ( CASQ2 ) have been linked to catecholaminergic polymorphic ventricular tachycardia (CPVT). The mechanisms leading to the clinical phenotype are still poorly understood because only 1 CASQ2 mutation has been characterized in vitro. Methods and Results— We identified a homozygous 16-bp deletion at position 339 to 354 leading to a frame shift and a stop codon after 5aa (CASQ2 G112+5X ) in a child with stress-induced ventricular tachycardia and cardiac arrest. The same deletion was also identified in association with a novel point mutation (CASQ2 L167H ) in a highly symptomatic CPVT child who is the first CPVT patient carrier of compound heterozygous CASQ2 mutations. We characterized in vitro the properties of CASQ2 mutants: CASQ2 G112+5X did not bind Ca 2+ , whereas CASQ2 L167H had normal calcium-binding properties. When expressed in rat myocytes, both mutants decreased the sarcoplasmic reticulum Ca 2+ -storing capacity and reduced the amplitude of I Ca -induced Ca 2+ transients and of spontaneous Ca 2+ sparks in permeabilized myocytes. Exposure of myocytes to isoproterenol caused the development of delayed afterdepolarizations in CASQ2 G112+5X . Conclusions— CASQ2 L167H and CASQ2 G112+5X alter CASQ2 function in cardiac myocytes, which leads to reduction of active sarcoplasmic reticulum Ca 2+ release and calcium content. In addition, CASQ2 G112+5X displays altered calcium-binding properties and leads to delayed afterdepolarizations. We conclude that the 2 CASQ2 mutations identified in CPVT create distinct abnormalities that lead to abnormal intracellular calcium regulation, thus facilitating the development of tachyarrhythmias.