Germline mutations of the fumarate hydratase (FH, fumarase) gene are found in the recessive FH deficiency syndrome and in dominantly inherited susceptibility to multiple cutaneous and uterine leiomyomatosis (MCUL). We have previously reported a number of germline FH mutations from MCUL patients. In this study, we report additional FH mutations in MCUL and FH deficiency patients. Mutations can readily be found in about 75% of MCUL cases and most cases of FH deficiency. Some of the more common FH mutations are probably derived from founding individuals. Protein-truncating FH mutations are functionally null alleles. Disease-associated missense FH changes map to highly conserved residues, mostly in or around the enzyme's active site or activation site; we predict that these mutations severely compromise enzyme function. The mutation spectra in FH deficiency and MCUL are similar, although in the latter mutations tend to occur earlier in the gene and, perhaps, are more likely to result in a truncated or absent protein. We have found that not all mutation-carrier parents of FH deficiency children have a strong predisposition to leiomyomata. We have confirmed that renal carcinoma is sometimes part of MCUL, as part of the variant hereditary leiomyomatosis and renal cancer (HLRCC) syndrome, and have shown that these cancers may have either type II papillary or collecting duct morphology. We have found no association between the type or site of FH mutation and any aspect of the MCUL phenotype. Biochemical assay for reduced FH functional activity in the germline of MCUL patients can indicate carriers of FH mutations with high sensitivity and specificity, and can detect reduced FH activity in some patients without detectable FH mutations. We conclude that MCUL is probably a genetically homogeneous tumour predisposition syndrome, primarily resulting from absent or severely reduced fumarase activity, with currently unknown functional consequences for the smooth muscle or kidney cell.
Recent polymerase chain reaction data have shown that most human papillomavirus (HPV) genotypes associated with epidermodysplasia verruciformis (EV) are widespread; however, HPV5 associated with EV skin carcinomas has only rarely been detected in non-EV patients. To identify the reservoir of this virus, we examined 335 sera from different groups of patients for the presence of HPV5 antibodies by an enzyme-linked immunosorbent assay test based on HPV5 virus-like particles. The prevalence of antibodies reacting with HPV5 virus-like particles was found to be significantly higher in psoriatic patients (24.5%) than in other groups (2-5%), including patients with atopic dermatitis and renal transplant recipients. Analysis of scrapings of lesional and uninvolved skin by a nested polymerase chain reaction method, using degenerate EV HPV primers, disclosed HPV DNA in 91.7% of 48 psoriatic skin samples and 35.5% of 31 atopic dermatitis specimens. Eleven EV HPV genotypes, most frequently HPV5 and HPV36, and a putative novel genotype (PsoX1) were identified in psoriasis. Five EV HPV genotypes and two putative novel genotypes (ADX1 and ADX2) were detected in atopic dermatitis patients. HPV5 was not found in atopic dermatitis patients. Using type specific primers, HPV5, HPV36, and HPV1 were found in 89.4%, 84.2%, and 42.1% of specimens from psoriatic patients, whereas HPV36 was detected in 22.5% of specimens from atopic dermatitis patients. HPV16 was never detected. On the whole, 27 HPV5 and 13 HPV36 DNA variants were disclosed after sequencing amplification products. Our data confirm that EV HPV are widespread and point to psoriasis as a reservoir for HPV5. Whether HPV5 is involved in the pathogenesis of psoriasis remains to be determined.
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