Other FAES classes and ACMG Flashcards
FGFR3 1620C>A, p.N540L
Hypochondroplasia
AR phenocopy for familial adenomatous Polyposis
MUTYH related polyposis syndrome
Base excision repair gene
- Attenuated FAP phenotype
Colon, endometrial, small bowel, ureter/renal pelvis cancer
Lynch syndrome
MLH1, MSH2, MSH6, PMS2
How do you manage HNPCC?
Aspirin (may reduce ca risk)
- Colonoscopy at 20
- Pelvic exam/TVUS at 30
- EGD, UA at 30
SMAD4, BMPR1A
Juvenile Polyposis Coli
Colorectal and upper GI cancers
- 3-5 juvenile polyps
- SMAD4 also causes HHT
What are homozygotes of CAG polyglutamine repeat exapnsion disorders present with?
Same as heterozygotes
- mechanism is toxic GOF - homozygotes and heterozygotes have same phenotype
What marker is analyzed in forensic DNA analysis?
Short or Variable tandem repeats
- Highly polymorphic wiht low mutation rate
How many STR loci are used in CODIS?
originally 13, now 20 as of 2017
What information is contained in a BAM file?
NGS data aligned to a referece with coverage depth
What are the best tests for FMR1 expansion?
Fragile X 5’UTR CGG
- Triplet primed PCR, southern blot, or promoter methylation analysis
meconium ileus, fat/vitamin malabsorption, high LFTs, pulmonary infections
Cystic Fibrosis
CFTR
- Biliary Cirrhosis = 2nd cause of death after pulm infections
Recurrent respiratory infections, mild intestinal disease, elevated sweat choloride, CFTR normal
SCNN1
Epithelial Na channel
Mild CTFR phenocopy
How does ivacaftor work?
Potentiates CFTR channel
- For mutations that affect channel opening
( can be used in combo with lumacaftor for Phe508del)
What does lumacaftor do?
Helps get Phe508del CFTR to cell surface
-used in combo with ivacafor for Phe508del
What does tezacaftor do?
Help get mutant CFTR protein to cell surface
- Used in combo with ivacaftor
What does CFTR Phe508del do to protein function?
- Defect in processing -> misfolding -> stays in ER (localization problem)
If CFTR R117H is detected, what should you do next?
Look for 5T
- Poly T tract affects splicing - 9T = 100%, 5T = 10%
How do you interpret R117H and 5T in CFTR?
If R117H and 5T in cis -> phenotype variable depending on other allele (can be severe if Phe508del)
If R117H and 5T in trans, likely CBAVD
If 5T without R117H + another CF allele -> CBAVD or mild CF
If R117H without 5T, may be CBAVD (depends on other allele)
What does a negative result on CFTR carrier panel mean?
Risk is not zero, need to calculate posterior probability
What if oligonucleotide ligation assay?
Tests for multiple common mutation in parallel using PCR products. Often used for CFTR
Is the imprinted allele active or silent?
Silent
Breech position, hypotonia, low birth weight, undescended testicles, narrow bifrontal diameter, downturned corners of mouth, almont PF
PWS
Paternally expressed (maternally imprinted) genes on 15q11q13
Pat deletion > UPD > imprinting defect
- Hyperphagia -> obesity, tone improves, reduced salivation, small hands/feet, intellectual disability
Normal HC at birth -> Microcephaly by 2 years, large amplitude slow-spikes on EEG, copious saliva
Angelman
Mat expressed (pat imprinted) genes on 15q11q13, including UBE3A
Mat del > UBE3A > pat UPD > methylation defects
When is imprinting reversed?
Gametogenesis
- Defect can cause functional UPD
What tests can detect 99% of PWS and 80% of AS?
methylation analysis
- Southern blog with methylation sensitive restriction endonuclease (5-methylcytosine)
- PCR after treatment of DNA w/ bisulfite (unmethylated C converted into U)
What is the recurrent risk of PWS or AS?
UPD or deletion - 1/1000
Methylation (imprinting center) defect - up to 50%
Rearrangement - up to 25%
UBE3A mutation - up to 50% if maternal
What test will detect parent of origin inUPD?
Trio microsatellite analysis w/ STR markers
Methylation sensitive MLPA (does not need parental data)
What are the imprinted chromosomes?
6 - transient diabetes (PLAGL1, HYMA1)
7 - RSS
11 - BWS, RSS
14 - Temple syndrome (Pat imprinted), Kagami-Ogata syndrome (Mat imprinted) - both nonspecifi skeletal
15 - PWS, AS
20 - pseudo-hypoparathyroidism
omphalocele, hemihyperplagia, cytomegaly of fetal adrenal cortex, renal abnormalities
BWS
Loss of methylation of mat IC2 (50%) -> nRNA that promotes CDKN1C is is gone -> CDKN1C is suppressed
Pat UPD11 (20%)
Gain of methylation on mat IC1 (5%) -> mat IGF2 is expressed -> increased growth
Mat CDKN1C mutation (5%) -> growth suppressor stops working
hemihypotrophy, DD, trancular facies, IUGR
RSS
50% hypomethylation in pat 11p - Pat IGF1 no longer expressed
10% maternal UPD 7
Duplication of mat 11p - mat CDKN1C expressed twice
CYP2D6
CYP2D6
Converts codine to active opiate
- Rapid metabolizer -> avoid codine due to toxicity
- Reduced metabolizer -> start at higher dose, if not useful try different drug
- Poor metabolizer -> do not use as it will not work
CYP2C19
CYP2C19
Coverts clopidogrel to active form
Rapid metabolizer - use as recommended
Normal metabolizer - use as recommended
Intermediate metabolizer - use alternative
Poor metabolizer - use alternative
CYP2C9, VKORC1
CYP2C9, VKORC1
Predicts response to warfarin
- Faster metabolizer -> need higher doses to reach therapeutic range
What is resoluation of microarray?
200kb for deletion and 500kb for duplications
- good for microdeletion/microduplication syndromes
In array CGH, what is the log 2 ration of a heterogyzous deletion? Duplication?
Deletion = -1, Duplication = 0.6
What are disadvantages of SNP array vs array CGH?
- SNP arrays are based on known SNPs -> cannot be customized
- More probes needed
CNV characteristics:
- Well known, recurrent
- Published CNV w/ consistent phenotype
- Dose senstive disease causing gene in interval
- >3-5Mb
Pathogenic criteria
CNV charactersitics:
- Single case report with well defined phenotype
- CNV as compelling evidence of causing disorder relevant to clinical indication
Likely Pathogenic
CNV characteristics:
- No genes but exceeds reportable size (3-5Mb)
- Few genes, few CNBs reported in literature not in polymorphic region
Likely benign
CNV characteristics:
- Few genes, dosage senstivity not established
- No firm conclusion
VUS
What is the reportable size limit for CNVs?
3-5Mb
in a CMA, what is the lower limit of homozygosity for first-cousin relations?
4% homozygosity (predicted 6.25%)
What are strengths/weaknesses of MLPA vs exon-targeted array for exon level deletions?
MLPA pros:
only needs 1-2 probes per exon, robust results, more specific in region of homology
MLPA cons:
- Allele dropout -> false positive, breakpoint determination not as precise (only 1-2 probes vs many in CMA)
Macrocephaly, CAL spots, axillary freckling, lipomas
Legius syndrome
SPRED1
-NF like but no neurofibromas
CAL spots, meningiomas, schwannomas, hearing loss
NF2
Merlin/Schwannomin
CAL spots, lisch nodules, neurofibromas, medulloblastoma, colon cancer
Constitutional mismatch repair syndrome
MSH2, MSH6, MLH1, PMS2
- Allelic with Lynch, but homozygous
- NF + lynch cancers (Colon, endometrial, upper GI, etc)
+ CNS and Heme cancers (GBM, medulloblastoma, NH lymphoma)
What is the difference between type 1 and type 2 mosiacism?
Type 1 = both parents normal, some cells gain mutation -> AD disease
Type 2 = one mutant allele inherited form parent, some cells get second hit -> AR disease
Mosaic vs Chimera
Mosaic starts from single fertilized egg
Chimera starts from 2 fertilized eggs -> fuse
linear epidermal nevi, asymmetric growth, lipoatrophy, vascular malformation, lung bullae, ovarian cystadenoma, parotid adenoma
Proteus
AKT1 (downstream of PI3K)
- Cerebriform connective tissue nevus
Lipoatrophy, segmental overgrowth, venous anomalies, megalencephaly, capillary malformations
PIK3CA related overgrowth spectrum
- Overlaps with proteus (same pathway)
Most common genes for CDLS
NIPBL (60%) - AD
SMC1A (5%) - XL
HDAC8 (2%) - XL
What is the pathophys of CDLS?
Cohesin complex part of sister chromatid exchange, dsDNA repair, maintaning genome organizaion, and distal transcription
Tall forehead, deep philtrum, wide neck, low posterior hairline, sparse hair (infancy) -> thick,wooly hair (childhood), macrocephaly, low set ears
Noonan Syndrome
PTPN11 (50%, most common), SOS1 (10%, 2nd most common), RAF1 (3rd), KRAS, HRAS
+ Pulmonic stenosis, slow growth, GU anomalies, CAL spots, bleeding diathesis
SHOC2 p.S2G
Noonan with loose anagen hair
- Easily and painlessly pluckable, sparse, thin, slow-growing hair without sheaths
What gene causes Costello syndrome?
Noonan + papillomata
HRAS
What genes cause CFC syndrome?
Noonan + follicular hyperkeratosis, sparse/curly hair, absent eyebrows
BRAF, MEK1, MEK2
What cancer is associated with Noonan?
JMML
Name the mitochondrial disease associated with each phenotype:
- Renal tubulopathy, seizures, liver failure
- Ptosis, myopathy, ophthalmoplegia
- ophthalmoplegia, RP, ataxia, heart block, diabetes, hypoparathyroidism
- sideroblastic anemia, pancytopenia, exocrine pancreas failure
- cerebellar/brainstem strokes
- neuropathy, ataxia, RP
- RRF, seizures, stroke like episodes, cardiomyopathy, diabetes, hearing loss, RP, ataxia
- RRF, myoclonus, seizures, myopathy, optic atrophy, deafness, lipomas, neuropathy
- vision loss, dystonia
- Renal tubulopathy, seizures, liver failure - Alpers
- Ptosis, myopathy, ophthalmoplegia - CPEO
- ophthalmoplegia, RP, ataxia, heart block, diabetes, hypoparathyroidism - KSS
- sideroblastic anemia, pancytopenia, exocrine pancreas failure - Pearson
- cerebellar/brainstem strokes - Leigh
- neuropathy, ataxia, RP - NARP
- RRF, seizures, stroke like episodes, cardiomyopathy, diabetes, hearing loss, RP, ataxia - MELAS
- RRF, myoclonus, seizures, myopathy, optic atrophy, deafness, lipomas, neuropathy - MERRF
- vision loss, dystonia - LHON
where are alpha-satellite DNA located?
Centromeres
- 171bp tandem repeat
TTAGGG sequence
Telomere cap - substrate for telomerase and shortens with age
- Distal to subtelomeric repeats
What are characteristics of a dark band on G stain? What about R stain?
R = reverse G
Dark G = AT rich -> Gene sparse, early transcription, tissue specific
How many chiasma/chromosome is required for normal segregation?
At least one per chromosome arm
Which aneuploidy is 100% maternal M1 error?
Trisomy 16
Which aneuoploidy is ~50/50 maternal vs paternal origin?
XXY
Which aneuploidy is mostly maternal MII error?
Trisomy 18
What percent of 45,X, Tiromy 18, Trisomy 21, and 47,XXY conceptuses are liveborn?
45,X - 1%
Trisomy 18- 5%
Trisomy 21 -20%
47 XXY, 47 XXX, 47, XYY - 80%
What is the empirical risk of unbalanced offspring (adjacent segregation -> livebirth) in parent with balanced translocation?
10-15%
What should you be concerned when parent w/ robertsonian translocation has a balanced offspring?
UPD 14 or 15
What disorder is associated with marker chromsome 15? 22?
15 - palister killian (temporalfronto balding)
22 - cat eye
What causes SBMA?
CAG repeat expansion in AR gene
>38 = full penetrance
<34 = normal
What causes hemophilia B leyden?
Factor 9 leyden
- Hemophilia B that resolves in puberty when androgen levels increase
- Caused by promoter mutation at -20
Where is poly T tract on CFTR?
Exon 8
- regulates splicing of exon 9 (skip if 5T)
when is a premature stop codon likely to result in truncated protein?
When it is within last 50bp of next to last exon, in last exon, or in single exon gene
What copy of SMN is telomeric?
SMN1
SMN2 is centromeric
erlotinib, getfitinib
EGFR targeting drugs
imatinib, dasatinib, nilotinib
BCR/ABL1 targeting drugs
Pantumumab, cetuximab
KRAS tageting drugs
what is the relationship between mutation rate and selection?
AD: u=sq
AR u=sq2
XL u=sq/3
1- senstivity
false negative rate
1- specificity
false positive rate
5 most common congenital anomalyes
1) undescended testes
2) CHD
3) Talipes
4) NTD
5) CL/P
normal intrinsic fetal development altered by mechnical force
deformation
normal intrinsic fetal develoment is interrupted by outside force
disruption
afternomal fetal tissue organization
dysplasia
morphological defect from abnormal intrinsic fetal development
malformation
t8:14
burkitt lymphoma
Activation of MYCC oncogene
crizotinib
ALK inihibitor
Used for recurrent ALK inversion in small cell lung ca
-ALK-EML4 fusion
vermurafinib
Target BRAF V600E
Melamonas
Erlotinib
target EGFR in lung ca
Vandetanib
Target RET in medullary thyroid ca
adrenocortical/choiroid plexus carcinoma, anaplastic rhabdomyosarcoma, hypodiploid ALL
TP53
Phenochromocytoma + paraganglioma
SDH
When do start surveillance for TP53?
breast MRI at 20, colonoscopy at 25
nail dystrophy, oral leukoplakia, reticulate skin pigmentation
Dyskeratosis congenita
Telomere dysfunction
+ hypoplastic bone marrow
-Very short telomeres
FAP management
Colonscopy at 10
EGD at 20
Thyroid exam
AR Familial polyposis
MUTYH
When do you start colonscopy for Juvenile polyposis?
15
what is the serious early complication in STK11?
Peutz -Jeghers
intussusception
CDH1
Hereditary diffuse gastric cancer and lobular breast cancer
PALB2
Breast and pancreatic ca
Olaparib
PARP inhibitor for BRCA tumors (especially ovarian)
When to start screening for BRCA?
Breast at 25, ovarian/prostate at 30
leiomyomatosis + RCC
fumarate hydratase
Chromophobe/oncycytic renal cancer
Birt-Hogg-Dube
FLCN - tumor suppressor gene
+ firbofolliuloma, polype, medullary thyroid, penumothorax
what is the probablity a women in genral population is a carrier for an XLR mutation?
4u
- new u on X from mom
- new u on X from dad
- mom is carrier
C = u + u +1/2C -> C = 4u
UCD with hepatic fibrosis
ASL deficiency
which AA are N-linked CDGs attached to?
asparagine
B glucoronidase
Sly syndrome
MPS VII
- Hurler like, can be very severe/hydrops
Premutation for Friedreich
GAA repeat in intron 1
34-66 = premutation
<33 is normal
>67 is pathological
What causes symptoms in Hartnup disease?
SLC6A19 - neutral AA transporter
low neural AA -> Tryptophan malabsorption -> niacin/serotonin deficiency -> Pellagra rash + ataxia
Tx : niacin
- Neutral AA low (but not proline, Arg Lys, Orn -> which are low in renal fanconi)
ZNF9
Myotonic dystrophy type 2
CCTG
>75 = pathogenic
Most common congenital anomalies related to obesity in mom
1) NTD
2) CHD
3) CL/P
ectodermal dysplasia with normal teeth, short stature, eye anomalies
Clouston syndrome
Skin + hair + nails
GJB6 (AD)
ectodermal dysplasia with normal skin and teeth
Witkop
MSX1 (AD)
X linked ichthyosis
Steroid sulfatase
Blistering in or above basal layer
EB simplex
- KRT5, KRT14, EXPH5
Blistering within basement membrane
Juncitonal EB
LAMB3, COL17A1
Blistering below basement membrane
Dystrophic EB
COL7A1
Blistering in multiple cleavage planes (within, above, and below basement membrane)
Kindler syndrome
Kindlin-1 (FERMT1)
Serpina1 Glu342Lys
A1AT Z allele
10% activity
mechanism of transient neonatal diabetes
overexpression of paternally expressed genes in chromosome 6
- Paternally UPD6 or maternal hypomethylation
TNFRSF13B
CVID
- humerol immunity issues after 2yrs (usually young adulthood)
- Tx IVIG
STAT3
Hyper IgE syndrome
AD
- high IgE, boils, cysts, eczema
IL2RG
XL SCID
XL alpha thalassemia
ATRX
alpha thal + ID, microcephaly, telecanthus, genital anomalies
Gonads in androgen insensitivy
XL- AR gene
- Female external genetalia, male gonads
XL salt wasting, hypoglycemia, and low BP
NROB1
XL congenital adrenal hypoplasia
asfotase alfa
Hypophosphatasia
high deoxypyridinoline/pyridinoline ratio in urine (HPLC)
EDS6 - kyphoscoliotic
PLOD1 -> deficient lysyl hydroxylase 1 activity
forrowed skin, droopy face, doughy skin without hyperelasticity
Cutis laxa
ATP6VOA1, EFEMP2, FBLN4, FBLN5
ABCC6
pseudoxanthoma elasticum
Skin papules, retinal streaks/hemorrhages, GI bleed, angina
cerebro-oto-renal syndrome
Lowe syndrome
OCRL -> part of PI pathway
- cataracts/glaucoma, CNS, renal fanconi
High uric acid, gout, renal failure
AD tubulointestinal kidney disease
- Uromodulin, Renin