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Cytogenetics > Syndromes (New) > Flashcards

Syndromes (New) Flashcards

1
Q

Trisomy 21

A

Down Syndrome

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2
Q

Tris 21 - Etiology

A

Extra chromosome 21: 47, XB, +21 OR extra piece of critical region (DSCR)

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3
Q

Tris21 - Genotype Origin

A

Usually from maternal Meiosis I non-disjunction (85-90%) so have two different homologs of 21 that are maternal, one that is paternal (i.e. none of these are sister chromatids, so none identical)
*Can also be paternal MII error
*Can also be due to Robertsonian parent (4%)
*Can also be parent with isochromosome 21 (1-2%)

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4
Q

Tris21 - Clinical Features

A
  • Hypotonia
  • Distinct facial features: almond shaped eyes, epicanthal folds, flat nasal bridge
    -Brushfield spots on eyes
    -Excess nuchal skin
    -Single transverse palmer crease
    -Clinodactyly
    -Cardiovascular defects in 40%
    -Intellectual disability
    -Transient myeloproliferative disorders in newborns and 500 fold higher risk of leukemia
    -Premature dementia (Alzheimer’s disease onset at 50 yo)
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5
Q

Trisomy 13

A

Patau Syndrome

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6
Q

Tris13 - Etiology

A

Trisomy of chromosome 13 (47,XX,+13)

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7
Q

Tris 13 - Genotype Origin

A

Maternal meiosis

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8
Q

Tris13 - Clinical Features

A

-Early lethality (median survival only 2.5 days and only 5% survive more than 6 months)
-Midline defects:
*Holoprosencephaly (failure of brain development)/microcephaly
*Cleft lip/palate
*Cutaneous scalp defects
*Congenital heart defects
*Omphalocele
-Polydactyly
-Renal abnormalities
-Severe ID
-IUGR

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9
Q

Trisomy 18

A

Edward Syndrome

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10
Q

Tris18 - Etiology

A

Trisomy of chromosome 18 (47,XY,+18)

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11
Q

Tris18 - Genotype Origin

A

Most due to error in maternal Meiosis II
*Risk increases with advanced maternal age

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12
Q

Tris18 - Clinical Features

A

-Early lethality (only 5-10% survive to 1 year)
-IUGR
-Microcephaly
-Omphalocele
-Cardiac defects
-Severe intellectual disability
-Clenched hand position
-Clubfoot or rocker bottom feet
-Small, low set ears

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13
Q

Trisomy 8 mosaicism syndrome

A

Mosaic Warkany syndrome

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14
Q

Tris8 mosaicism - Etiology

A

Trisomy of chromosome 8 in some cells

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15
Q

Tris8 mosaicism - Genotype Origin

A

Arises post zygotically (somatic) through nondisjunction in mitosis (de novo)

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16
Q

Tris8 mosaicism - Clinical Features

A

-Thick lips
-Camptodactyly
-Clinodactyly
-Deep plantar and palmer skin furrows
-kidney, cardiac, skeletal abnormalities
-Skin hyper pigmentation
-Males more frequently affected than females

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17
Q

Tetrasomy 12p

A

Pallister-Killian Syndrome

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18
Q

Tetrasomy 12p - Etiology

A

Extra isochromosome of 12p, resulting in tetrasomy of 12p (always mosaic b/c some cells lose the isochromosome early in development)

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19
Q

Tetrasomy 12p - Clinical Features

A

-Course face
-Hypopigmented streaks/spots
-Severe ID
-Accessory nipples
-Cardiac anomalies
-Diaphragmatic hernia
- Only see in chromosomes of skin fibroblasts (not in blood cells)

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20
Q

San Luis Valley Syndrome - Etiology

A

Recombinant 8: dup(8q) and del(8p)

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21
Q

San Luis Valley Syndrome - Genotype Origin

A

Parent with a pericentric inversion on Chr 8: inv(8)(p23.1q22.1)

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22
Q

Prader-Willi Syndrome - Etiology

A

UPD of 15: only maternal genome (trisomy rescue of 15)

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23
Q

Angelman Syndrome - Etiology

A

UPD of 15: only paternal genome (trisomy rescue of 15)

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24
Q

22q11.2 Deletion Syndrome

A

DiGeorge Syndrome, Velocardiofacial Syndrome, Conotrunacal Anomaly Face syndrome, Shprintzen Syndrome, Cayler Cardiofacial Syndrome

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25
Q

22q11.2 Deletion Syndrome - Etiology

A

22q11.2 deletion (interstitial)
-Three different sizes: 3Mb, 1.5 Mb, 2 Mb
-Critical region: TBX1 with others having additional symptoms

26
Q

22q11.2 Deletion Syndrome - Clinical Features

A

-Variable penetrance with very different symptoms
-ID/DD
-Cardiac malformations (VSD, Tetralogy of Fallot, Aortic arch anomalies)
-Immune deficiency (t-cell deficiency, autoimmune)
-Palatal issues (Cleft palate, speech delay, hypernasal speech)
-Dysmorphic facial features (may be subtle)
-Psychiatric illness (Schizophrenia, ADD, ASD, behavioral differences)
-Parathyroid disfunction (hypocalcemia)
-Many others

27
Q

22q11.2 Deletion Syndrome - Phenocopies

A
  • DiGeorge Type 2 (deletion on 10p)

-CHARGE Syndrome (single gene mutation)

28
Q

22q11.2 Duplication Syndrome - Etiology

A

Duplication of 22q11.2 (3 Mb or 1.5 Mb) (interstitial)

29
Q

22q11.2 Duplication Syndrome - Clinical Features

A

-Milder than del
-Heart defects, urogenital anomalies, cleft palate, feeding problems, hearing impairment, facial dysmorphism, mild ID or LD

30
Q

Wolf-Hirschhorn Syndrome - Etiology

A

-Deletion of 4p16 (terminal deletion)
-Deletion size can be
* Mild: <3.5 del
* Classic: 5-18 Mb del
* Severe: 20-25 del
-Critical region: WHSCR and WHSCR-2
* Deletion of either enough to cause symptoms

31
Q

Wolf-Hirschhorn Syndrome - Clinical Features

A

-“Greek Warrior Helmet”: beaked nose, hypertelorism, protruding eyes, short philtrum, micrognathia, poorly formed ears with pits/tags, microcephaly, asymmetrical features, downturned mouth
-Hypospadias
-Ocular colobomas
-ID (in severe: psychotic behavior)
-Microcephaly
-Seizures
-Hearing loss
-Wide variety in phenotype
- Many others

32
Q

Cri Du Chat Syndrome - Etiology

A

Deletion of variable breakpoints on 5p (terminal and interstitial) (3-5MB)
-Zone in middle: if deleted no symptoms

33
Q

Cri Du Chat Syndrome - Clinical Features

A

-Cat like cry in infancy (larynx malformation)
-Microcephaly
-Severe psychomotor retardation
-ID
-Facial dysmorphology
* Prominent mouth
* Hypertelorism
* Low set ears
* Down slanting palebral fissures
* Epicanthal folds
* Open mouth expression
-Infrequently: cleft lip, heart defects, male genital anomalies, renal anomalies, syndactyly
-Hyperactivity

34
Q

Williams Syndrome - Etiology

A

-Interstitial microdeletion of 7q11.23 (1.5 Mb)
-Critical region: WSCR (114 kb) - includes elastin (ELN) gene + others (ELN gene only = supravalvular aortic stenosis SVAS)

35
Q

Williams Syndrome - Clinical Features

A

-Cardiovascular disease: Supravalvular Aortic Stenosis
-Facial dysmorphism: wide mouth, broad forehead, full cheeks in childhood
-Endocrine abnormalities: hypercalcemia, hypercalcuria
-Strengths in language and short term memory
-Unique personality: Friendly, empathetic, anxious, ADD (“Cocktail Personality”)
-Extreme weakness in visuospatial construction
-Stellate/Lacy Iris
-Others

36
Q

7q11.2 Duplication Syndrome - Etiology

A

Duplication of 7q11.23 (interstitial)

37
Q

7q11.2 Duplication Syndrome - Clinical Features

A

-Language delay, mildly impaired nonverbal and visuospatial skills
-Anxiety, social phobia, delayed social skills, autism
-Distinctive facial features
-Macrocephaly
-Cardiovascular disease
-Neurological symptoms

38
Q

Smith Magenis Syndrome - Etiology

A

Interstitial deletion of 17p11.2 (~3.7 Mb)
-Critical region: Retinoic Acid Inducer 1 (RAI1)
-Usually de novo

39
Q

Smith Magenis Syndrome - Clinical Features

A

-Facial dysmorphism: course facial features
* Deep set eyes,
* tented upper lip
* broad square face
* brachycephaly
* Midface hypoplasia
-Inverted sleep patterns
-Large size/obesity
-“Self hug”
-Lick and flip
-Middle ear anomalies
-Laryngeal anomalies
-ID/DD
-Short stature
-Immune disfunction
-Nail yanking/scratching
-Others

40
Q

Potocki-Lupski Syndrome - Etiology

A

-Interstitial duplication of 17p11.2 (~3.7 Mb, but can be smaller)
-RAI1 dosage sensitivy implicated

41
Q

Potocki-Lupski Syndrome - Clinical Features

A

-Sleep apnea
-Global DD/ID
-Autistic features
-Anxiety
-Short stature
-Structural cardiovascular anomalies
-Facial dysmorphism: gentle downslant palebral fissures, abnormal ears, triangular face in young children, oval shaped face in older children

42
Q

Klinefelter Syndrome - Etiology

A

47,XXY (or even three/four/five Xs: the more X’s the worse the intellectual phenotype)

43
Q

Klinefelter Syndrome - Genotype Origin

A

50/50 maternal/paternal errors: maternal MI or MII, paternal MI
-Caused when XpYp recombination at PAR1 fails
-Mosaicism common b/c often kick out extra X post-zygotically

44
Q

47,XYY

A

Jacobs Syndrome

45
Q

47,XYY - Etiology

A

Extra Y

46
Q

47,XYY - Genotype Origin

A

Non-disjunction at paternal meiosis II (YY sperm)

47
Q

47,XYY - Clinical Features

A

-Mild phenotype
-Tall
-Mild learning disability/language delays
-IQ lower than siblings
-ADD and ADHD
-Normal fertility

48
Q

47,XXX

A

Triple X Syndrome

49
Q

47,XXX - Etiology

A

3 Xs, overexpression of non-inactivated genes on the inactive X’s

50
Q

47,XXX - Clinical Features

A

-Mild phenotype (only ~10 diagnosed)
-Somewhat tall
-Clinodactyly
-Fertile
-Some: renal/genitourinary abnormalities, seizures, premature ovarian failure
-Some learning deficits (IQ lower than sibs)

51
Q

Turner Syndrome

A

45,X (Monosomy X)

52
Q

Turner Syndrome - Etiology

A
  • 45,X (monosomy X)
  • commonly mosaic (often confined placental mosaicism)
  • Often have mosaic Y: cancer risk for gonadal tumors (if high percentage have Y  usually male phenotype, more Klinefelter)
  • Variants can have loss of just parts of Xq or Xp
    -if fertile can pass on the abnormal X to daughters (lethal in males)
    -One variant: isoXq (loss of Xp, but trisomy of Xq)
53
Q

Turner Syndrome - Critical Regions

A
  • physical phenotype Xp, ovarian function Xq,
  • In PAR1: SHOX gene  haploinsufficiency leads to short stature
54
Q

Turner Syndrome - Clinical Features

A

-Short stature
-Lymphedema of hands and feet
-Redundant nuchal folds
-Hyperconvex nails
-Cardiovascular abnormalities (coarctation of the aorta)
-Streak ovaries
-Infertility (degeneration of oocytes during fetal development)

55
Q

Triploidy - Etiology

A
  • Examples: 69,XXX; 69,XXY; 69, XYY
  • Cause:
    *Haploid egg fertilized by two haploid sperm
    *Haploid egg fertilized by one diploid sperm
    *Diploid egg fertilized by haploid sperm (most common)
  • Digynic (two maternal genomes): Normal NT, smaller placenta, higher viability
  • Diandric (two paternal genomes): Lower viability, maternal complication risk, Partial molar pregnancy cause
56
Q

Cat Eye Syndrome - Etiology, Clinical Features

A
  • supernumerary derivative chromosome 22 (duplication)
  • Coloboma (cleft in pupil of eye)
57
Q

Emanuel Syndrome - Etiology

A

Supernumerary der(22)t(11;22)

58
Q

Emanuel Syndrome - Clinical Features

A

-MCA
-Conotruncal heart defects
-Microcephaly
-Cleft palate
-Micrognathia
-Skin tags/pits
-Genital abnormalities
-DD/ID
-Imperforate anus
-Facial features: round face, deep set eyes, prominent forehead, course face

59
Q

Di George Syndrome II - Etiology, Clinical Features

A

-Etiology: deletion on 10p
-Typical 22q11.2 phenotype with hearing loss and ptosis

60
Q

Aneuploidies

A

Down Syndrome, Trisomy 13, Trisomy 18, Mosaic Trisomy 8, Pallister-Killian Syndrome, Klinefelter Syndrome, Jacobs Syndrome, Triple X Syndrome, Turner Syndrome, Triploidy, Cat-Eye Syndrome, Emanuel Syndrome

61
Q

Imprinting (UPD) Syndromes

A

Prader-Willi Syndrome, Angelman Syndrome, Russel-Silver

62
Q

Dup/Del (Contiguous Gene) Syndromes

A

San Luis Valley Syndrome, 22q11.2 Deletion Syndrome, 22q11.2 Duplication Syndrome, Wolf-Hirschhorn Syndrome, Cri Du Chat Syndrome, Williams Syndrome, 7q11.2 Duplication Syndrome, Smith Magenis Syndrome, Potocki-Lupski Syndrome, DiGeorge II

Cytogenetics (3 decks)

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