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Genetics Flashcards

1
Q

Fragile X Syndrome

A
  • Most common inherited and 2nd most common congenital cause of intellectual disability
  • x-linked d/o c/b loss of function mutation in FMR1
  • trinucleotide repeat = (CGG)n
  • females with 1 abnormal X have milder and variable sx

Features:

  • long, narrow face
  • prominent forehead and chin
  • large testes
  • hyperlaxity of hand joints
  • developmental delay (speech and motor) in infancy
  • neuropsych sx in childhood (e.g. anxiety, ADHD, autism spectrum)
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2
Q

Number 1 cause of congenital intellectual disability

A

Down Syndrome

  • epicanthal folds
  • upslanting palpebral features
  • low-set small ears
  • flat facial profile
  • sandle-toe deformity
  • single palmar crease
  • Brushfield spots (in iris)
  • duodenal atresia
  • congenital heart dz (ASD)
  • inc risk of ALL and Alzheimer’s dz (>35 yo)

Quad screen: dec alpha-fetoprotein, dec estriol, inc inhibin A, inc beta-hCG

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3
Q

Ehlers-Danlos syndrome

A

connective tissue d/o

most common mutation = type V collagen production

sx = skin hyperelasticity and fragility, joint laxity

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4
Q

Klinefelter syndrome

A

47, XXY

mild ID
tall stature
gynecomastia
small testes (often undescended)
infertility
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5
Q

Marfan syndrome

A

AD, fibrillin-1 gene mutation–> connective tissue d/o

  • tall stature
  • arachnodactyly (long and thin fingers)
  • ectopia lentis (lens displacement)
  • dilation of proximal aorta –> dissectic aortic aneurysms
  • inc arm:height ratio
  • dec upper:lower body segment ratio
  • pectus excavatum
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6
Q

Prader Willi syndrome

A

paternal deletion of part of chromosome 15

infancy –> hypotonia and associated gross motor delays, hyperphagia and associated obesity

ID and behavioral problems common (e.g. autistic behaviors, OCD features)

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7
Q

Wilson disease

A

dx = dec serum ceruloplasmin, inc hepatic copper

cirrhosis, CNS involvement, Kayser-Fleischer rings

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8
Q

Hemochromatosis

A

dx = high serum ferritin levels

cirrhosis, pancreatic fibrosis, subsequent DM, CM (cardiomyopathy), secondary hypogonadism

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9
Q

Fabry Disease

A

inherited deficiency of alpha-galactosidase A

globoside ceramide trihexoside accumulates in tissues

sx = hypohidrosis, acroparesthesia (episodic burning neuropathic pain in extremities) and angiokeratomas (punctate dark non-blanching macules and papules between umbilicus and knees)

tx = enzyme replacement therapy to avoid renal failure and death

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10
Q

alpha 1 antitrypsin deficiency

A

panacinar emphysema and liver cirrhosis

alpha 1 antitrypsin = serine protease inhibitor that normally inactivates elastase and trypsin

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11
Q

Lesch-Nyhan

A

sx = spasticity, choreoathetoid movement, self-mutilation

c/b HGPRT absence (which converts hypoxanthine to IMP and guanine to GMP) –> defective purine salvage pathway –> excess uric acid production and de novo purine synthesis
“He’s Got Purine Recovery Trouble”

X-linked recessive

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12
Q

Niemann-Pick disease

A

spasticity

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13
Q

Adenosine deaminase deficiency

A

excess ATP and dATP –> feedback inhibition of ribonucleotide reductase –> prevents DNA synthesis –> decreased lymphocyte count –> SCID

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14
Q

Achondroplasia

A

AD

cell-signaling defect in fibroblast growth factor (FGF) receptor 3 –> dwarfism, short limbs, larger head, normal trunk, i.e. Tyrion Lannister

assoc. with advanced paternal age

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15
Q

ADPKD

A

AD

  • always b/l
  • massive kidneys from cysts
  • sx = flank pain, hematuria, HTN, progressive RF

85% 2/2 PKD1 mutation (chromosome 16)

assoc. conditions:
- polycystic liver dz
- berry aneurysms
- mitral valve prolapse

*infantile form = recessive

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16
Q

Familial adenomatous polyposis

A

AD

colon covered with polyps after puberty –> colon cancer unless resected

mx on chromosome 5 in APC gene

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17
Q

Familial hypercholesterolemia (hyperlipdemia type IIA)

A

AD

Elevated LDL due to defective or absent LDL receptor

heterozygotes (more common) = LDL ~300
homozygotes (rare) = LDL ~700+

severe atherosclerosis at young age, tendon xanthomas (esp Achilles), MI before age 20

18
Q

Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome)

A

AD

inherited d/o of blood vessels

findings: telangiectasiasm recurrent epistaxis, skin discolrations, AVMs

19
Q

Hereditary spherocytosis

A

AD

spectrin and ankyrin defect –> spherocytes

findings: hemolytic anemia, inc MCHC

cure = splenectomy

20
Q

Huntington’s disease

A

AD

findings: depression, progressive dementia, choreiform movements, caudate atrophy, and dec levels of GABA and ACh in the brain

sx onset = 20-50 yo

trinucleotide repeat (CAG)n on chromosome 4

“hunting 4 food”

21
Q

MEN 1

A

AD

pituitary, parathyroid, pancreas

22
Q

MEN 2A

A

AD

pheochromocytoma, parathyroid hyperplasia, medullary thyroid cancer

ret gene

23
Q

MEN 2B

A

AD

pheochromocytoma, medullary thyroid cancer, marfanoid habitus, mucosal neuromas

ret gene

24
Q

Neurofibromatosis type 1 (von Recklinghausen’s disease)

A

AD

cafe au lait spots, neural tumors, Lisch nodules (pigmented iris hamartomas), scoliosis, optic pathway gliomas

long arm of chromosome 17

25
Q

NFT2

A

b/l acoustic schwannomas, juvenile cataracts

NF2 gene on chromosome 22

26
Q

Tuberous sclerosis

A

AD

facial lesions (adenoma sebaceum, hypopigmented “ash leaf spots”, cortical and retinal hamartomas, sz, ID, renal cysts, renal angiomyolipomas, cardiac rhabdomyomas, inc incidence of astrocytomas

incomplete pentrance

4 systems affected = CNS, skin, cardiac, renal

27
Q

von Hippel-Lindau disease

A

AD

hemangioblastomas or retina/cerebellum/medulla

multiple b/l RCC and other tumors

deletion of VHL gene (tumor suppressor) on chrom 3p –> constitutive expression of hypoxia inducible factor HIF-1 (TF) and activation of angiogenic GFs and EPO –> inc vascular endothelial growth

pheochromocytomas can occur in conjunction

28
Q

Cystic Fibrosis

A

AR defect in CFTR on chromosome 7 (commonly del of Phe 508) –> misfolding and degradation of channel before reaching cell surface

sx= chronic bronchitis, recurrent PNA (s. aureus, pseudomonas), bronchiectasis, pancreatic insufficiency (steatorrhea, malabsorption), nasal polyps, meconium ileus, infertility in males due to absent vas deferens b/l, fat-soluble vit deficiencies (ADEK), failure to thrive

dx = Cl sweat test showing Cl elevation 
tx = N-acetylcysteine to loosen mucus plugs (cleaves S-S bonds in mucus glycoproteins)
29
Q

CFTR

A
  • Cl secretion in lungs and GI tract
  • Cl reabsorption from sweat

most commonly a deletion at position 508 of codon coding for phenylalanine

can also be c/b frameshift mx

30
Q

X-linked recessive d/o

A

“Be Wise, Fool’s GOLD Heeds Silly HOpe”

Bruton's agammaglobulinemia
Wiskott-Aldrich syndrome
Fabry's disease
G6PD deficiency
Ocular albinism
Lesch-Nyhan syndrome
Duchenne's (and Becker's) muscular dystrophy
Hunter's Syndrome
Hemophilia A and B, Ornithine transcarbamoylase deficiency
31
Q

Duchenne’s muscular dystrophy

A

x-linked frameshift mutation –> del of dystrophin gene (fxn = anchor muscle fibers) –> accelerated muscle breakdown

sx = weakness in pelvic girdle muscles and progresses superiorly, calf pseudohypertrophy, cardiac myopathy, Gower’s maneuver

dx = inc CPK and muscle biopsy

onset before 5 yo k

32
Q

Becker’s muscular dystrophy

A

mx in dystrophin gene but less severe than Duchenne

onset = adolescence or early adulthood

33
Q

Trinucleotide repeat expansion disease

A

“Tried HUNTING for MY FRIED eggs(X)”
“X-Girlfriend’s First Aid Helped Ace My Test”

Fragile X - CgG –> c guy’s giant junk
Friedreich’s ataxia - CaA
Huntington’s disease - CaG –> hunting to cage
Myotonic dystrophy - CtG –> can’t try to game too weak

34
Q

Edward’s syndrome

A

trisomy 18

severe ID, rocker-bottom feet, micrognathia, low-set ears, clenched hands, prominent occiput, congenital heart disease

death by 1 yo

quad screen: dec alpha-fetoprotein, dec beta-hCG, dec estriol, nl inhibin A

35
Q

Patau’s syndrome

A

trisomy 13

severe ID, rocker-bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, congenital heart disease

death by 1 year

1st trimester screen: dec free beta-hCG, dec PAPP-A, inc nuchal translucency

36
Q

Cri-du-chat syndrome

A

Congenital microdeletion of short arm of chromosome 5 (46, XX or XY, 5p-)

microcephaly, moderate to severe ID, high-pitched crying/mewing, epicanthal folds, cardiac abnormalities (VSD)

37
Q

Williams syndrome

A

Congenital microdeletion of long arm of chromosome 7 including elastin gene

distinct elfin facies, ID, hypercalcemia (inc sensitivity to vit D), well-developed verbal skills, extreme friendliness with strangers, CV problems

38
Q

22q11 deletion syndromes

A

CATCH-22 thanks to microdeletions and aberrant development of 3rd and 4th branchial pouches

Cleft palate
Abnormal facies
Thymic aplasia --> TC deficiency
Cardiac defects 
Hypocalcemia 2/2 parathyroid aplasia

DiGeorge = thymic, parathyroid, and cardiac defects
Velocardiofacial syndrome - palate, facial, and cardiac defects

39
Q

Robertsonian translocation

A

nonreciprocal
commonly involves pairs 13, 14, 15, 21, 22

long arms of 2 acrocentric chrom (i.e. centromeres near ends) fuse at centromere and 2 short arms lost

40
Q

Bruton’s X-linked agammaglobulinemia

A

p/w recurrent sinopulmonary infections, Giardia lamblia gastroenteritis, failure to thrive, low of all Ig levels, inc risk of pyogenic (encapsulated) bacT infection

mx in Bruton tyrosine kinase –> failure of BM pre-B cells (CD19+, CD20+) to develop into mature BCs (CD19+, CD20+ CD21+).

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