Muscular Dystrophy Flashcards
What age does Duchenne muscular dystrophy present?
2-3 years
At what age do Duchenne muscular dystrophy patients require a wheelchair?
12 years
In Duchenne and Becker muscular dystrophy which muscles are affected most by weakness?
Starts in trunk but spreads to arms and legs
Legs get weak first
Hard to run, jump, or climb stairs
What age does Emery-Dreifuss muscular dystrophy present?
Ages 10 to 20 years
In Emery-Dreifuss muscular dystrophy which muscles are affected most by weakness?
Weakness starts in arms and later affects legs too
Sometimes face weakens a little
What are other problems associated with Emery-Dreifuss muscular dystrophy?
Heart problems
Contractures
What age does limb girdle muscular dystrophy present?
Childhood or later
In limb girdle muscular dystrophy which muscles are affected most by weakness?
Shoulders and hips
What age does facioscapulohumeral muscular dystrophy present?
Usually affects people ages 20 to 30 years but can happen younger
In facioscapulohumeral muscular dystrophy which muscles are affected most by weakness?
Face muscles get so weak a person cannot smile, whistle, or shut his or her eyes tight
Weakness affects legs; shoulders and upper arms
What age does congenital muscular dystrophy present?
Birth
In congenital muscular dystrophy which muscles are affected most by weakness?
Many muscles; this is sometimes called “floppy baby”
What are the initial labs ordered in muscular dystrophy?
CK, CMP, TSH, T4, ESR
What is the testing strategy in DMD?
Del/dup analysis first (80%) followed by sequencing
In the absence of family history, what is the chance that a person’s mother is a carrier of DMD (with an affected proband)?
2/3
What is the cardiac finding in female carriers of DMD and what percentage are affected?
8% develop DCM
What is the onset of Beckers muscular dystrophy?
5-60 years
What genes are associated with facioscapulohumeral muscular dystrophy?
DUX4 (AD) part of the D4Z4 macrosatellite repeat
SMCHD1 (<5%)
What gene causes oculopharyngeal muscular dystrophy?
PABPN1 (AD)
What are the features of oculopharyngeal muscular dystrophy?
Affects eyelids, throat, facial, and limbs
Difficulty swallowing and keeping eyes open
Onset 40-50s
What is the genetic cause of myotonic dystrophy type 1 (DM1)?
CTG trinucleotide repeat in the DMPK gene (AD)
What is the presentation of MILD myotonic dystrophy type 1 (DM1)?
Mild myotonia
Normal life span
Onset 20-70
What is the presentation of CLASSIC myotonic dystrophy type 1 (DM1)?
Cataracts
Baldness
Muscle weakness and wasting
Myotonia
Cardiac conduction issues
Shortened life span
Onset 10-30 years
What is the presentation of CONGENITAL myotonic dystrophy type 1 (DM1)?
Hypotonia at birth
Respiratory insufficiency and early death
ID
What are the CTG repeat lengths in myotonic dystrophy?
Premutation: 35-49
Mild: 50-150
Classic: 100-1000
Congenital: >1000
What is the genetic cause of myotonic dystrophy Type 2?
CCTG repeats in the CNBP gene (AD)
What is the CK level in DMD/BMD
CK up to 20X normal
What percentage of LGMD is AR and what are the two most common genes associated with the condition?
90%
CAPN3
DYSF
What is pleiotrophy?
Mutations in the same gene with different phenotypes?
e.g. LGMD2 and Myoshi distal myopathy
What are some classical clues of LGMD hip girdle?
Falls on uneven surfaces
Need to use arms on a chair/table to pull self up
Cannot get out of booths/trucks
What are some classical clues of LGMD shoulder girdle?
Uses elbows to feed self
Cannot lift objects (grocery bags)
What are the genetic causes of Emery-Dreifuss MD?
X-linked:
EMD
FHL1
AD/AR:
LMNA
