R. B. van der Luijt

Molecular genetic tests as a guide to surgical management of familial adenomatous polyposis

BACKGROUND In familial adenomatous polyposis the only curative treatment is colectomy, and the choice of operation lies between restorative proctocolectomy (RPC) and colectomy with ileorectal anastomosis (IRA). The RPC procedure carries a higher morbidity but, unlike IRA, removes the risk of subsequent rectal cancer. Since the course of familial adenomatous polyposis is influenced by the site of mutation in the polyposis gene, DNA analysis might be helpful in treatment decisions. METHODS We evaluated the incidence of rectal cancer in polyposis patients who had undergone IRA, and examined whether the requirement for subsequent rectal excision because of cancer or uncontrollable polyps was related to the site of mutation. FINDINGS Between 1956 and mid-1995, 225 patients registered at the Netherlands Polyposis Registry had undergone IRA. In 87 of them, a pathogenetic mutation was detected. 72 patients had a mutation located before codon 1250 and 15 patients after this codon. The cumulative risk of rectal cancer 20 years after surgery was 12%, and at that time 42% had undergone rectal excision. The risk of secondary surgery was higher in patients with mutations in the region after codon 1250 than in patients with mutations before this codon (relative risk 2.7, p < 0.05). INTERPRETATION On this evidence, IRA should be the primary treatment for polyposis in patients with mutations before codon 1250, and RPC in those with mutations after this codon.

Germline mutations in the 3′ part of APC exon 15 do not result in truncated proteins and are associated with attenuated adenomatous polyposis coli

Abstract Familial adenomatous polyposis (FAP) is an inherited predisposition to colorectal cancer characterized by the development of numerous adenomatous polyps predominantly in the colorectal region. Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for most cases of FAP. Mutations at the 5′ end of APC are known to be associated with a relatively mild form of the disease, called attenuated adenomatous polyposis coli (AAPC). We identified a frameshift mutation in the 3′ part of exon 15, resulting in a stop codon at 1862, in a large Dutch kindred with AAPC. Western blot analysis of lymphoblastoid cell lines derived from affected family members from this kindred, as well as from a previously reported Swiss family carrying a frameshift mutation at codon 1987 and displaying a similar attenuated phenotype, showed only the wild-type APC protein. Our study indicates that chain-terminating mutations located in the 3′ part of APC do not result in detectable truncated polypeptides and we hypothesize that this is likely to be the basis for the observed AAPC phenotype.

Classification of BRCA1 missense variants of unknown clinical significance

Background:BRCA1 is a tumour suppressor with pleiotropic actions. Germline mutations in BRCA1 are responsible for a large proportion of breast–ovarian cancer families. Several missense variants have been identified throughout the gene but because of lack of information about their impact on the function of BRCA1, predictive testing is not always informative. Classification of missense variants into deleterious/high risk or neutral/low clinical significance is essential to identify individuals at risk. Objective: To investigate a panel of missense variants. Methods and results: The panel was investigated in a comprehensive framework that included (1) a functional assay based on transcription activation; (2) segregation analysis and a method of using incomplete pedigree data to calculate the odds of causality; (3) a method based on interspecific sequence variation. It was shown that the transcriptional activation assay could be used as a test to characterise mutations in the carboxy-terminus region of BRCA1 encompassing residues 1396–1863. Thirteen missense variants (H1402Y, L1407P, H1421Y, S1512I, M1628T, M1628V, T1685I, G1706A, T1720A, A1752P, G1788V, V1809F, and W1837R) were specifically investigated. Conclusions: While individual classification schemes for BRCA1 alleles still present limitations, a combination of several methods provides a more powerful way of identifying variants that are causally linked to a high risk of breast and ovarian cancer. The framework presented here brings these variants nearer to clinical applicability.

Multiple endocrine neoplasia type 1 (MEN1) : its manifestations and effect of genetic screening on clinical outcome

Objective  Effect of genetic screening on outcome in multiple endocrine neoplasia type 1 (MEN1) remains unclear. Expression of MEN1 is described using currently available diagnostic techniques. Manifestations and outcome are compared in patients diagnosed because of clinical expression with those diagnosed by genetic screening.

Genotype-phenotype correlations in families with deletions in the von Hippel-Lindau (VHL) gene.

Abstract. Von Hippel-Lindau (VHL) disease is a hereditary tumor syndrome characterized by predisposition for bilateral and multi-centric hemangioblastoma in the retina and central nervous system, pheochromocytoma, renal cell carcinoma, and cysts in the kidney, pancreas, and epididymis. We describe five families for which direct sequencing of the coding region of the VHL gene had failed to identify the family-specific mutation. Further molecular analysis revealed deletions involving the VHL gene in each of these families. In four families, partial deletions of one or more exons were detected by Southern blot analysis. In the fifth family, FISH analysis demonstrated the deletion of the entire VHL gene. Our results show that (quantitative) Southern blot analysis is a sensitive method for detecting germline deletions of the VHL gene and should be implemented in routine DNA diagnosis for VHL disease. Our data support the previously established observation that families with a germline deletion have a low risk for pheochromocytoma. Further unraveling of genotype-phenotype correlations in VHL disease has revealed that families with a full or partial deletion of the VHL gene exhibit a phenotype with a preponderance of central nervous system hemangioblastoma.

Cryptic von Hippel-Lindau disease: germline mutations in patients with haemangioblastoma only

OBJECTIVES Central nervous system haemangioblastoma (HAB) is a major feature of von Hippel-Lindau (VHL) disease, and it is estimated that about 30% of HAB patients have VHL disease. Consequently, it is widely recommended that sporadic HAB patients are screened for clinical and radiological features of VHL disease because of the risk of multiple tumours. We investigated the frequency of VHL germline mutations in patients with HAB only with no clinical or radiological evidence of VHL disease to define the role of molecular genetic analysis in the management of such patients. METHODS Eighty four patients with a single HAB (23 Dutch, 61 UK) and four with multiple HAB (two Dutch, two UK) were studied by direct sequencing of the coding region and quantitative Southern blotting. RESULTS AVHL germline mutation was found in three of 69 (4.3%) single HAB patients aged 50 years or less (three of 84 (3.6%) total single HAB patients). A germlineVHL mutation was detected in a 44 year old woman with a solitary cerebellar HAB, as well as in four clinically unaffected close relatives, and in two single HAB cases presenting at the ages of 29 and 36 years. Germline VHL mutations were detected in two of four cases with multiple HAB. CONCLUSIONS Early detection of VHL disease is important to reduce morbidity and mortality and therefore we recommend that, in addition to conventional clinical and radiological investigations, VHL gene mutation analysis should be offered to all HAB patients younger than 50 years. HAB patients aged >50 years will have a lower a priori risk of VHL disease and further data are required to evaluate the role of routine molecular genetic investigations in late onset HAB cases. The failure to detect germline VHL mutations in some patients with multiple HAB may indicate the presence of somatic mosaicism or additional HAB susceptibility genes.

Frequency of Von Hippel-Lindau germline mutations in classic and non-classic Von Hippel-Lindau disease identified by DNA sequencing, Southern blot analysis and multiplex ligation-dependent probe amplification

The current clinical diagnosis of Von Hippel‐Lindau (VHL) disease demands at least one specific a sporadic VHL manifestation in a patient with familial VHL disease, or, in asporadic patient, at least two or more hemangioblastomas or a single hemangioblastoma in combination with a typical visceral lesion. To evaluate this definition, we studied the frequency of germline VHL mutation in three patients groups: (i) multi‐organ involvement (classic VHL), (ii) limited VHL manifestations meeting criteria (non‐classic VHL) and (iii) patients with VHL‐associated tumors not meeting current diagnostic VHL criteria. In addition, we validated multiplex ligation‐dependent probe amplification (MLPA) as a rapid and reliable quantitative method for the identification of germline VHL deletions. The frequency of germline VHL mutations was very high in classic VHL cases with multi‐organ involvement (95%), lower in non‐classic cases that meet current diagnostic criteria but have limited VHL manifestations or single‐organ involvement (24%) and low (3.3%), but tangible in cases not meeting current diagnostic VHL criteria. The detection of germline VHL mutations in patients or families with limited VHL manifestations, or single‐organ involvement is relevant for follow‐up of probands and early identification of at‐risk relatives.

Primary hyperparathyroidism in MEN1 patients: a cohort study with longterm follow-up on preferred surgical procedure and the relation with genotype.

Objective:To identify the optimal surgical strategy for multiple endocrine neoplasia type 1 (MEN1)–related primary hyperparathyroidism (pHPT). To describe the course of postoperative hypoparathyroidism and to assess whether genotype is associated with persistent/recurrent pHPT. Background:Surgery is the preferred treatment in MEN1-related pHPT, but the surgical procedure of choice is still uncertain. Methods:This retrospective cohort study was performed at the Departments of Endocrinology of the University Medical Centers of Utrecht and Nijmegen, the Netherlands. Patients were selected from the Dutch MEN1 database, including all patients 16 years or older treated for MEN1 from 1990 to 2009. Data were collected by medical record review. Results:Seventy-three patients underwent parathyroid surgery. Persistent/recurrent pHPT occurred in 53% after less than 3 parathyroids resected (<SPTX), 17% after subtotal resection (SPTX), and 19% after total resection with autotransplantation (TPTX). Persistent (≥6 months) postoperative hypoparathyroidism occurred in 24% after <SPTX, 39% after SPTX, and 66% after TPTX. Median duration of hypoparathyroidism was 1.5 years, in 65% successful cessation of vitamin D/calcium was possible, even after more than 10 years. After <SPTX, patients with nonsense or frameshift mutations in exons 2, 9, and 10 had a significantly lower risk of persistent/recurrent pHPT than patients with other mutations. After SPTX/TPTX persistence/recurrence did not differ with genotype. After SPTX/TPTX persistence/recurrence was more frequent (P = 0.07) in patients without bilateral transcervical thymectomy (TCT). Conclusions:SPTX with bilateral TCT is the procedure of choice for MEN1-related pHPT. Genotype seems to affect the chance of recurrence. Postoperative hypoparathyroidism lasting 6 months or more should not be considered permanent in MEN1.

Clinical management of Von Hippel–Lindau (VHL) disease

Von Hippel-Lindau (VHL) disease is an autosomal, dominant inherited tumour syndrome with an estimated prevalence of 2-3 per 100,000 persons. A germline mutation in the VHL gene predisposes carriers to tumours in multiple organs. These tumours may include haemangioblastoma in the retina and central nervous system (CNS), renal cell carcinoma, phaeochromocytoma, islet cell tumours of the pancreas, and endolymphatic sac tumours, as well as cysts and cystadenoma in the kidney, pancreas, epididymis and broad ligament. Penetrance of VHL disease is high, most carriers of a VHL germline mutation develop one or more tumours by the age of 60 years. The most common symptoms include: loss of vision, raised intracranial pressure, neurological deficits, paroxysmal raised blood pressure and local pain. At present, metastases from renal cell carcinoma and neurological complications from cerebellar haemangioblastoma are the most common causes of death. However, it is anticipated that intensive radiological and clinical monitoring, and advanced operation techniques will reduce both morbidity and mortality in patients with VHL disease.

Psychosocial impact of Von Hippel-Lindau disease: levels and sources of distress.

Lammens CRM, Bleiker EMA, Verhoef S, Hes FJ, Ausems MGEM, Majoor‐Krakauer D, Sijmons RH, Luijt van der RB, Ouweland van den AMW, Van Os Tam, Hoogerbrugge N, Gomez‐Garcia EB, Dommering CJ, Gundy CM, Aaronson NK. Psychosocial impact of von Hippel–Lindau disease: levels and sources of distress.