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CF Case Studies

SCOBEC & Birmingham Case Studies Training Day. CF Case Studies. Frances Bond West Midlands Regional Genetics Laboratory 15/10/08. Cases. Case 1- CM & AK Echogenic bowel carrier testing referral Case 2 – RC Meconium ileus diagnostic referral. Case 1 – CM & AK. Pregnant women and partner

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CF Case Studies

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  1. SCOBEC & Birmingham Case Studies Training Day CF Case Studies Frances Bond West Midlands Regional Genetics Laboratory 15/10/08

  2. Cases • Case 1- CM & AK • Echogenic bowel carrier testing referral • Case 2 – RC • Meconium ileus diagnostic referral

  3. Case 1 – CM & AK Pregnant women and partner CF carrier tests - Echogenic bowel

  4. Case 1 – CM & AK 0.1-0.2% of pregnancies Several causes including: Normal variant - with no apparent cause Resolves itself with no known effect on the health of the child Prenatal manifestation of meconium ileus ~11% of CF-affected foetuses ~1.3% of foetuses with echogenic bowel have CF Can vary to up ~6% due to the subjectivity of diagnosing echogenic bowel Echogenic Bowel

  5. Case 1 – CM & AK ARMS29 Upper controls p. Phe508del allele Normal allele atp. Phe508del locus Lower controls • CM and AK both p. Phe508del heterozygotes

  6. Case 1 – CM & AK • At least 1 in 4 risk foetus affected with CF • Offer to test amniocentesis sample to determine CF status of foetus if required

  7. Case 1 – CM & AK Prenatal Test • Amniocentesis sample tested to determine the CF status of the foetus • Unfortunately, MCC testing inconclusive • Cultured amniocytes • ARMS29 assay: p. Phe508del heterozygote • No evidence of MCC

  8. Case 1 – CM & AK • Foetus is a carrier of cystic fibrosis but is not predicted to be affected • Cytogenetic and QF-PCR results also negative • Sadly, foetus spontaneously aborted soon after

  9. Case 2 - RC • 8 day old male • CF diagnosis test – meconium ileus

  10. Case 2 - RC ARMS29 Upper controls p. Arg117His allele p. Phe508del allele Normal allele atp. Phe508del locus Lower controls p. Phe508del and p. Arg117His compound heterozygote

  11. Case 2 - RC PolyT assay Effect of p. Arg117His mutation is modulated by size of polyT tract C = Control P = Patient RC 9T allele 7T allele 5T allele Heterozygous for 5T and 9T alleles

  12. Case 2 - RC Interpretation p.Phe508del muation always in cis with 9T allele 5T allele must be in cis with p.Arg117His • Classical CF with pancreatic sufficiency

  13. Case 2 - RC • Not diagnosed as part of neonatal screening programme • Average IRT result: 64 – below cut-off for molecular analysis • IRT testing known to be inaccurate in cases with meconium ileus

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