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Background: Familial hypercholesterolemia (FH) is an autosomal dominant disease characterized by elevated plasma levels of LDLcholesterol that confers an increased risk of premature atherosclerotic cardiovascular disease. Early identification and treatment of FH patients can improve prognosis and reduce the burden of cardiovascular mortality.Aim of this study was to perform the mutational analysis of FH patients identified through a collaboration of 20 Lipid Clinics in Italy (LIPIGEN Study). Methods: We recruited 1592 individuals with a clinical diagnosis of definite or probable FH according to the Dutch Lipid Clinic Network criteria. We performed a parallel sequencing of the major candidate genes for monogenic hypercholesterolemia (LDLR, APOB, PCSK9, APOE, LDLRAP1, STAP1). Results: A total of 213 variants were detected in 1076 subjects. About 90% of them had a pathogenic or likely pathogenic variants. More than 94% of patients carried pathogenic variants in LDLR gene, 27 of which were novel. Pathogenic variants in APOB and PCSK9 were exceedingly rare. We found 4 true homozygotes and 5 putative compound heterozygotes for pathogenic variants in LDLR gene, as well as 5 double heterozygotes for LDLR/APOB pathogenic variants. Two patients were homozygous for pathogenic variants in LDLRAP1 gene resulting in autosomal recessive hypercholesterolemia. One patient was found to be heterozygous for the ApoE variant p.(Leu167del), known to confer an FH phenotype. Conclusions: This study shows the molecular characteristics of the FH patients identified in Italy over the last two years. Full phenotypic characterization of these patients and cascade screening of family members is now in progress.

Background Exome sequencing is a promising tool for gene mapping in Mendelian disorders. We utilized this technique in an attempt to identify novel genes underlying monogenic dyslipidemias. Methods and Results We performed exome sequencing on 213 selected family members from 41 kindreds with suspected Mendelian inheritance of extreme levels of low-density lipoprotein (LDL) cholesterol (after candidate gene sequencing excluded known genetic causes for high LDL cholesterol families) or high-density lipoprotein (HDL) cholesterol. We used standard analytic approaches to identify candidate variants and also assigned a polygenic score to each individual in order to account for their burden of common genetic variants known to influence lipid levels. In nine families, we identified likely pathogenic variants in known lipid genes (ABCA1, APOB, APOE, LDLR, LIPA, and PCSK9); however, we were unable to identify obvious genetic etiologies in the remaining 32 families despite follow-up analyses. We identified three factors that limited novel gene discovery: (1) imperfect sequencing coverage across the exome hid potentially causal variants; (2) large numbers of shared rare alleles within families obfuscated causal variant identification; and (3) individuals from 15% of families carried a significant burden of common lipid-related alleles, suggesting complex inheritance can masquerade as monogenic disease. Conclusions We identified the genetic basis of disease in nine of 41 families; however, none of these represented novel gene discoveries. Our results highlight the promise and limitations of exome sequencing as a discovery technique in suspected monogenic dyslipidemias. Considering the confounders identified may inform the design of future exome sequencing studies.

Chronic constipation that is unresponsive to laxative treatment is a severe illness, but children unresponsive to laxatives have been successfully treated with an elimination diet. We report the first cases of refractory chronic constipation caused by food hypersensitivity in adults. Four patients with refractory constipation who were unresponsive to high doses of laxatives were put on an oligo-antigenic diet and underwent successive double-blind, placebo-controlled, food challenges (DBPFC). Routine laboratory tests, immunological assays, colonoscopy, esophago-gastroduodenoscopy and rectal and duodenal histology were performed. While on an elimination diet, bowel habits normalized in all patients and a DBPFC challenge triggered the reappearance of constipation. In comparison with another 13 patients with refractory constipation unresponsive to the elimination diet, observed over the same period, the patients with food-hypersensitivity-related constipation had the following characteristics: longer duration of illness (p B/0.03), lower body mass index (p B/0.03), higher frequency of self-reported food intolerance (p B/0.01), higher frequency of nocturnal abdominal pain and anal itching (p B/ 0.01). In patients with food hypersensitivity, hemoglobin concentrations and peripheral leukocytes were lower than those in controls (p B/0.03). The duodenal and rectal mucosa histology showed lymphocyte and eosinophil infiltration, and the duodenal villi were flattened in two cases. In adult patients, refractory chronic constipation may be caused by food hypersensitivity and an elimination diet is effective in these subjects.

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