Double heterozygosity for BRCA1 and hMLH1 gene mutations in a 46-year-old woman with five primary tumors.

Germline mutations in BRCA1 and BRCA2 genes predispose to hereditary breast cancer, whereas carriers of mutations in any of the mismatch repair genes (MMR; hMLH1, hMSH2, hMSH6, hPMS2) are highly susceptible to Lynch syndrome. In the present study, we describe a woman affected by unilateral breast cancer at the age of 35 years. After 4 years, during the follow-up she developed synchronous (and asymptomatic) endometrial cancer, ovarian carcinoma and renal clear cell carcinoma. After 7 years (at age 46), the patient developed an infiltrating carcinoma of the contralateral breast and died in a few months of metastatic disease. Initial investigations led to the detection of a constitutional mutation in the BRCA1 gene. The extended genealogical tree disclosed a suspected history of colorectal carcinoma in the maternal branch. Endometrial cancer of the proband was investigated for microsatellite instability (MSI) and immunohistochemical expression of MLH1, MSH2 and MSH6 proteins. An high MSI status and lack of expression of MLH1 protein were detected. hMLH1 gene sequencing revealed the presence of a constitutional mutation, which was also found in the mother of the proband. Loss of the wild-type hMLH1 allele was detected in both breast tumors, thus suggesting that the MMR defect contributed to the development of the breast cancer.

Hypertriglyceridaemia and low plasma HDL in a patient with apolipoprotein A-V deficiency due to a novel mutation in the APOA5 gene.

APOA5 encodes a novel apolipoprotein (apo A-V) which appears to be a modulator of plasma triglyceride (TG). In apoA5 knock out mice plasma TG level increases almost fourfold, whereas in human APOA5 transgenic mice it decreases by 70%. Some SNPs in the APOA5 gene have been associated with variations in plasma TG in humans. In addition, hypertriglyceridaemic (HTG) patients have been identified who carried rare nonsense mutations in the APOA5 gene (Q139X and Q148X), predicted to result in apo A-V deficiency. In this study we report a 17-year-old male with high TG and low high density lipoprotein cholesterol (HDL-C), who at the age of two had been found to have severe HTG and eruptive xanthomas suggesting a chylomicronaemia syndrome. Plasma postheparin LPL activity, however, was normal and no mutations were found in LPL and APOC2 genes. The sequence of APOA5 gene revealed that the patient was homozygous for a point mutation (c.289 C>T) in exon 4, converting glutamine codon at position 97 into a termination codon (Q97X). Apo A-V was not detected in patient's plasma, indicating that he had complete apo A-V deficiency. The administration of a low-fat and low-oligosaccharide diet, either alone or supplemented with omega-3 fatty acids, started early in life, reduced plasma TG to a great extent but had a negligible effect on plasma HDL-C. Loss of function mutations of APOA5 gene may be the cause of severe HTG in patients without mutations in LPL and APOC2 genes.