High proportion of large genomic deletions and a genotype phenotype update in 80 unrelated families with juvenile polyposis syndrome.
BACKGROUND
In patients with juvenile polyposis syndrome (JPS) the frequency of large genomic deletions in the SMAD4 and BMPR1A genes was unknown.


METHODS
Mutation and phenotype analysis was used in 80 unrelated patients of whom 65 met the clinical criteria for JPS (typical JPS) and 15 were suspected to have JPS.


RESULTS
By direct sequencing of the two genes, point mutations were identified in 30 patients (46% of typical JPS). Using MLPA, large genomic deletions were found in 14% of all patients with typical JPS (six deletions in SMAD4 and three deletions in BMPR1A). Mutation analysis of the PTEN gene in the remaining 41 mutation negative cases uncovered a point mutation in two patients (5%). SMAD4 mutation carriers had a significantly higher frequency of gastric polyposis (73%) than did patients with BMPR1A mutations (8%) (p<0.001); all seven cases of gastric cancer occurred in families with SMAD4 mutations. SMAD4 mutation carriers with gastric polyps were significantly older at gastroscopy than those without (p<0.001). In 22% of the 23 unrelated SMAD4 mutation carriers, hereditary hemorrhagic telangiectasia (HHT) was also diagnosed clinically. The documented histologic findings encompassed a wide distribution of different polyp types, comparable with that described in hereditary mixed polyposis syndromes (HMPS).


CONCLUSIONS
Screening for large deletions raised the mutation detection rate to 60% in the 65 patients with typical JPS. A strong genotype-phenotype correlation for gastric polyposis, gastric cancer, and HHT was identified, which should have implications for counselling and surveillance. Histopathological results in hamartomatous polyposis syndromes must be critically interpreted.
Aretz
S
S
Institute of Human Genetics, University of Bonn, Wilhelmstrasse 31, D-53111 Bonn, Germany. stefan.aretz@ukb.uni-bonn.de
Stienen
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Uhlhaas
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Stolte
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Entius
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Loff
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Back
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Kaufmann
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Keller
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Blaas
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Siebert
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Vogt
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Spranger
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Holinski-Feder
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Sunde
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Propping
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Friedl
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D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D015703:Antigens, CD; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000172:deficiency / Q000235:genetics*; D015820:Cadherins / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D002872:Chromosome Deletion; D004252:DNA Mutational Analysis; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000453:epidemiology / Q000235:genetics*; D018740:Genetic Heterogeneity; D005838:Genotype; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007223:Infant; D044483:Intestinal Polyposis / Q000453:epidemiology / Q000235:genetics*; D008297:Male; D009386:Neoplastic Syndromes, Hereditary / Q000453:epidemiology / Q000235:genetics*; D021141:Nucleic Acid Amplification Techniques; D051059:PTEN Phosphohydrolase / Q000172:deficiency / Q000235:genetics*; D010641:Phenotype; D017354:Point Mutation; D051901:Smad4 Protein / Q000172:deficiency / Q000235:genetics*; D013683:Telangiectasia, Hereditary Hemorrhagic / Q000453:epidemiology / Q000235:genetics
D015703:Antigens, CD; C513384:CDH1 protein, human; D015820:Cadherins; C497796:SMAD4 protein, human; D051901:Smad4 Protein; C498211:BMPR1A protein, human; D052005:Bone Morphogenetic Protein Receptors, Type I; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human