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MSKD week 2 > clinical presentations > Flashcards

clinical presentations Flashcards

1
Q

what can be used to help diagnose benign joint hypermobility?

A

Beighton’s Criteria

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2
Q

what is included in Beighton’s criteria?

A

a point for each:
-passive opposition of thumb to forearm
-passive extension of pinky finger (V-MCP)
-active hyperextension of elbow
-active hyperextension of knee
-ability to flex spine placing palms to floor w/o bending knees

5/9 –> hypermobile joints

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3
Q

key features of ehlers-danlos syndrome:

A

-fragility of soft CT
-easily damaged/stretched/bruised skin
-pain
-increased flexibility
-early arthritis

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4
Q

what is vascular type ehlers danos?

A

-severe form
-skin isn’t stretchy, rather THIN and TRANSLUCENT
-excessive bruising/visible veins
-high rate of arterial rupture, aortic root dilation

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5
Q

what mutation causes ehler-danlos?

A

COL5A1, COL5A2 (encode for production of alpha chain of type V collagen)

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6
Q

characteristics of Marfan syndrome?

A

thin and distensible skin
joint laxity
long, narrow extremities
tall
ectopia lentis
aortic root dilation, acute dissection, aneurysms

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7
Q

what mutation causes Marfan?

A

FBN1 gene (encodes for fibrillin-1)

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8
Q

what criteria is used to Dx Marfan?

A

Ghent criteria

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9
Q

what two signs are positive for those with Marfan?

A

Steinburg sign - thumb inside clenched fist extends past hand
Walker Murdoch - thumb to finger around wrist overlap

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10
Q

Duchenne syndrome inheritance pattern:

A

young males
X linked recessive

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11
Q

what criteria/classification is used for suspected ehlers-danlos syndrome patients?

A

Villefranche classification

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12
Q

Duchenne syndrome onset:

A

severe, earlier onset
2-3 years old

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13
Q

key features of Duchennes:

A

-muscle weakness
-calf pseudo hypertrophy
-scoliosis/lumbar lordosis
-club foot
-joint contractures

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14
Q

what mutation causes Duchennes?

A

X linked recessive (hemizygous, males)
nonsense/frameshift mutation of Xp21.2 dystrophin gene
dystrophin protein ABSENT

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15
Q

what is the function of dystrophin protein?

A

-links intracellular actin with the “dystrophin-associated glycoprotein complex” (DGC)
-DGC - links cytoskeletal actin and extraceullular matrix while stabilizing the sarcolemma
without dystrophin, sarcolemma wilts and becomes unstable

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16
Q

what clinical findings indicate Duchennes?

A

Gower’s sign
Trendelenburg sign
elevated creatine phosphatase kinase (CPK)
muscle biopsied showing absent dystrophin
EMG

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17
Q

treatment for Duchennes:

A

steroids
rehab
eteplirsen - antisense oligonucleotide?

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18
Q

what is Trendelenburg sign?

A

waddling gait due to muscle weakness

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19
Q

Beckers muscular dystrophy inheritance pattern:

A

mostly young males (hemizygous - 1 copy)
X linked recessive

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20
Q

Beckers onset:

A

a milder MD
onset around age 10-20
longer life expectancy than Duchennes

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21
Q

key features of Beckers:

A

-calf pseudohypertrophy
-dilated cardiomyopathy

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22
Q

what clinical findings indicate Beckers?

A

-Gowers sign
-elevated CPK levels
-muscle biopsy showing DECREASED dystrophin
-EMG
-ICG for cardiomyopathy

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23
Q

treatment for Beckers:

A

steroids and rehab

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24
Q

main differences between Duchennes and Beckers:

A

Duchennes:
more severe, earlier onset, shorter life expectancy, absent dystrophin

Beckers:
milder form, later onset, longer life expectancy, decreased dystrophin, more prone to dilated cardiomyopathy

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25
Q

what is syndactyly?

A

congenital bone disorder - failure of digits to separate during development due to a combination of genetic and environmental factors

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26
Q

inheritance pattern of syndactyly?

A

-autosomal dominant, autosomal recessive, or X linked recessive
more common in other genetic syndromes (i.e. trisomy 21)

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27
Q

most common syndactyly presentation?

A

3rd and 4th finger fusion
bilateral involvement (50% of people)

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28
Q

associated findings of Marfan syndrome?

A

-pectus excavatum, pectus carinatum
-scoliosis
-spondylolithesis
-protrusion acetabuli
-arachnodactyly
-pes planus (flat feet)

29
Q

types of syndactyly:

A

simplex (soft tissue) vs complex (soft tissue + bone)
complete (to fingertips) vs incomplete (not to fingertips)

30
Q

what is osteogenesis imperfecta?

A

weak bones that fracture easily
“brittle bone disease”

31
Q

what mutations cause osteogenesis imperfecta?

A

autosomal dominant mutations in COL1A1 or COL1A2 –> affect type 1 collagen synthesis

32
Q

how does osteogenesis imperfecta affect the eyes?

A

sclera is made of type I collagen
sclera becomes so thin that it looks blue as the blue choroidal vessels are visible underneath

33
Q

how does osteogenesis imperfecta affect the ears?

A

fractures and dislocations of the ossicles
leading to hearing loss

34
Q

how does osteogenesis imperfecta affect teeth?

A

type 1 collagen –> dentin
therefore, teeth wear easily

35
Q

what characteristic sets ehlers-danlos apart from Marfan?

A

it has stretchy skin, Marfan does not

36
Q

what is osteopetrosis?

A

thick and heavy bones that fracture easily
“stone bone”

37
Q

what mutation causes osteopetrosis?

A

-autosomal dominant or recessive
-mutation in carbonic anhydrase II
-this enzyme typically allows osteoclasts to secrete protons to maintain an acidic environment for bone resorption
-osteoblasts still build as normal (hence, stone bone)

38
Q

clinical findings of osteopetrosis?

A

-frequent fractures
-hearing and vision loss
-hydrocephalus
-cytopenias (osteoblasts replace bone marrow with bone)

39
Q

treatment for osteopetrosis?

A

bone marrow transplant
osteoclasts derived from monocytes in the marrow

40
Q

what is achondroplasia?

A

skeletal dysplasia that results in dwarfism
lack of cartilage development

41
Q

inheritance pattern of achondroplasia:

A

autosomal dominant

42
Q

mutation that causes achondroplasia:

A

FGFR3 - fibroblast growth factor 3
regulates how collagen turns into bone
mutation –> decreased bone production and decreased growth

43
Q

why do those with dwarfism have short limbs but normal sized heads and torsos?

A

-FGFR3 mutation only inhibits bone formation that comes from a cartilage template (echondral ossification)
-extremities only
-face, skull, and ribs –> inter membranous ossification

44
Q

what genetic concept is demonstrated through dystrophinopathies?

A

allelic heterogeneity
Duchennes and Beckers have different mutations on the same locus –> causing similar presentations

45
Q

how do Beckers and Duchennes affect females?

A

-depends on the lyonization pattern (one X chromosome is inactivated)
-if more cells express the defected dystrophin gene –> manifesting carriers/show sx
-phenotypic variation

46
Q

who is susceptible to Lyonization?

A

those with 2+ X chromosomes
XX (normal female)
47 XXY (aneuploidy)

47
Q

inheritance pattern of myotonic dystrophies?

A

autosomal dominant

48
Q

type 1 myotonic dystrophy mutation:

A

trinucleotide repeat (CTG) in untranslated 3’ region of DMPK gene (chromosome 19q)

regulates gene expression! translated into myotonic dystrophy protein kinase and inhibits myosin phosphatase (involved in muscle relaxation and contraction)

49
Q

type 2 myotonic dystrophy mutation:

A

CNBP (chromosome 3q)
tetranucleotide repeat (CCTG)
repeats found in the first intron of CNBP
translated into cellular nucleic acid binding protein

50
Q

what causes the nucleotide repeat expansion in myotonic dystrophies?

A

slipped nucleotide mispairing
DNA polymerase loses its place and keeps adding to the repeats, expanding the number of repeats

51
Q

what genetic phenomenon is demonstrated by myotonic dystrophies?

A

anticipation –> each successive generation has more nucleotide repeats and more severe symptoms because DNA polymerase keeps expanding the repeats. a pre-mutation allele can become a full mutation in the next generation.

52
Q

disease mechanism of DM1?

A

toxic DMPK pre-mRNA accumulation sequesters and binds muscle bind-like protein (MBNL), preventing it from leaving nucleus. MBNL normally has splicing function.

53
Q

normal function of MBNL protein

A

splicing function
downstream effects of cell growth signaling, cardiac development, sarcomere stabilization

54
Q

what are the 2 types of DM1?

A

congenital form
adult form

55
Q

clinical presentation of adult form DM1?

A

facial muscle weakness, hollow cheeks, drooping eyelids, weakness of distal hand muscles and lower leg, toe and foot drop

56
Q

clinical presentation of DM2?

A

-milder muscle weakness, mostly affecting PROXIMAL muscles of the thighs and hip and shoulder and elbows
-difficulty climbing stairs, rising from seated position, holding/lifting objects

57
Q

commonality between both types of DM?

A

both cause myotonia - sustained muscle contractions, difficulty relaxing after use. unable to release hand shake.

58
Q

other common features of DM?

A

cataracts, insulin resistance, cardiac conduction effects, abnormalities in electrical activity of heart

triangle shaped mouth

59
Q

how can mitochondrial myopathies be characterized?

A

neuromuscular disorders, dysfunctional mitochondria with the inability to produce enough ATP
most affected tissues = brain and skeletal (need high ATP)
usually, mutations in mitochondrial DNA (mtDNA) that encode for ETC subunits

60
Q

inheritance pattern of mitochondrial genes:

A

exclusively maternal inheritance
only biological FEMALES can pass onto offspring
father’s mitochondria left behind during fertilization

61
Q

what genetic concept is demonstrated by mitochondrial inheritance?

A

heteroplasmy - daughter cells receive a mixture of WT and mutant mitochondria

mutant has to exceed threshold level for sx to emerge

62
Q

what is homoplasmy?

A

daughter cell inherits pure sample - either all WT or all mutant (by chance)

63
Q

main clinical features of mitochondrial myopathies:

A

pleiotropy - a gene can influence the development of multiple phenotypes

-fatigue
-myalgia
-vision loss, ptosis (drooping eye), ocular dysmotility (abnormal eye alignment/movement)
-seizures, hearing loss, impaired coordination, cognitive deficits

64
Q

MELAS acronym:

A

Mitochondrial Encephalomyopathy Lactic Acidosis Stroke like sx

65
Q

mutation that causes MELAS:

A

mitochondrial gene MT-TL1
encodes for mitochondrial tRNA leucine

66
Q

MELAS clinical features:

A

-muscle fatigue, exercise intolerance
-lactic acid buildup
-fatigue, muscle weakness, abd pain, vomiting, difficulty breathing
-stroke like sx - AMS, hemiparesis, hemianopia
-severe HA and seizures
-weight loss

-repeated stroke like sx can lead to blindness, movement problems, and dementia

67
Q

exam findings for MELAS:

A

-elevated lactate and CK in blood
-analyze genes coding for ETC enzymes
-muscle biopsy –> RAGGED RED FIBERS in Gomori trichrome staining

68
Q

what are the ragged red fibers in MELAS?

A

compensatory proliferation of abnormal mitochondria in affected muscles

MSKD week 2 (8 decks)

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