2. OBJECTIVES
Review the pluses and minuses of the
current diagnostic tools
Illuminate some pitfalls we might be able to
fall into less often
Shorten and reduce costs of the diagnostic
odyssey, while enhancing our likelihood of
success and benefit for our patients
Make the case for a true interdisciplinary
effort in neuromuscular diagnosis
3. WHAT’S WRONG WITH THIS PICTURE?
Credit: Jain Foundation, LGMD2I foundation
4. WHAT DIFFERENCE DOES IT MAKE?
Identify the medical risks
Genetic counseling accuracy
Cardiac
Pulmonary
Anesthesia/malignant hyperthermia
Diabetes, scoliosis, HCM
Retinopathy, hearing loss
XLR vs AR
XLSD vs AD vs mito
In some cases, clinical treatments or clinical trials may be
available depending on the specific genetic diagnosis
Prognosis, what to expect/what helps, support groups
5. THE TOOLS FOR DIAGNOSIS - $
Family history
Physical exam
Misdiagnosis, misreport, actually getting records
Limited by cooperation
UMN vs LMN, on a good day
Cerebellar versus proprioceptive ataxia
Muscle bulk, contracture, facial function, EOM, winging,
microcephaly
Metabolic (non-genetic lab) tests
Sometimes specific and quick. Sometimes not.
CPK, aldolase, TFT
AA, OA, isoelectric transferrin, CoQ10, vitamins
Lactate/pyruvate – lots of false + and –
Alpha-fetoprotein
CSF studies
6. THE TOOLS FOR DIAGNOSIS – $$
Electrodiagnosis
Biopsy
Myopathic vs neuropathic, axonal vs demyelination
Kids hate it.
Especially repetitive stim, which is not always clear
Myotonia is not as specific a finding as you’d like and may not be
there in all “myotonic” disorders
May be a quick answer for floppy baby (SMA yes or no)
UMN lesion can be confounding
Very specific for compressive and radicular pathology
More likely specific especially on immunostaining or EM
Pitfalls with related protein staining affected
May be nonspecific myopathic or even normal in some conditions
Issues with specimens for send out – research vs clinical
Muscle Imaging
Fatty infiltration vs inflammation
Affected vs unaffected muscles
7. THE TOOLS FOR DIAGNOSIS – $$-$$$
Specific single gene tests
PANELS
The good, the bad and the ugly
AVOID CMTD, HSP, SCA, DM – not supposed to be “orderable” here
Some cover better than WES for specific conditions
Microarrays, snp arrays
When common things occur commonly or single best explanation fits
pretty well
Yield about 15%, towards 20%
Now requires consent
Regions of homozygosity, duplications, deletions
Whole Exome
Requires genetics consultation
Expensive and not always covered for parent
Best chance for diagnosis of rare condition if Brad Schaefer does not
know what it is off the top of his head
Tool for discovery of new genes
9. CHARCOT MARIE TOOTH DISEASE(S)
Supect:
Options: Edx or PMP22 dup gene test alone first
Distal weakness, cavus, hypo or areflexia,
Commonly +FH, “clumsy”
Typical, PN only, no need for other screenings
If atypical at all, CMT1x, MPZ, MFN also reasonable to do
Edx for slow, very slow, or normal (demyelinating, intermediate, or
axonal)
Partial panel vs whole exome
DO NOT GET THE FULL PANEL
1a-f = AD, demyelinating
2a-p = AD, axonal
4a-j = AR, demyelinating, internediate or axonal
X1-5 (not 3a-e) “ ”
Mito and nuclear mito (e.g. PDH), HSANs, SCAs, leukodystrophies
also cause hereditary neuropathy
10. NERVE BIOPSY??
Dejerine-Sottas not genetically specific
PMP22, EGR2 (CMTD 1D, 4E), MPZ, PRX
Vasculitic, infectious or other acquired
Sural (sensory) or epidermal for small-fiber
Gene test might be better for amyloid (TTN)
Portugese variant 50%
Fabry, Tangier, giant axonal neuropathy
Reference:
http://archneur.jamanetwork.com/article.aspx?articleid=782848
11. DYSTROPHINOPATHY
Suspects
CPK 4-5 figures, not clinically a myositis
Utah dystrophinopathy (or other) gene test
Leiden reading frame checker
Clinicaltrials.gov
Biopsies?
Global delay in a boy as well as abnormal gait
Elevated “LFT” no jaundice, alk phos, GGT OK
Floppy baby with contiguous gene syndrome
Rhabdmyolysis
Research purposes
Negative gene test
Edx not helpful
12. MYOTONIA
Suspects for myotonic dystrophy
Myotonia not always present on Edx early
At ACH – get only DM1 for number of repeats NOT PANEL
Myotonia Congenita is different disease
Clubfoot, floppy, facial weakness, global delay
May be premie and look like or have CP also
Adult with cataract, DM, low energy, temporal wasting
Becker/Thomsen
Strength low for degree of muscle bulk, warm-up
CLCN1, SCN4a
Also consider
Thyroid disorders
Other channelopathies (e.g. KCNJ2/Tawil-Anderson short QT)
Brody myopathy (ATP2a1)
Some LGMD (especially 1c)
14. ANTERIOR HORN CELL DISEASE
Edx faster,
should be
confirmed
Rough
correlation with
SMN2 copies
and severity
Biopsy may also
be diagnostic,
with group
atrophy, not
often required
Other rare
conditions
HBSMA
SMARD
DSMA - UE
AMC
15. SCA, HSP
Friedreich’s ataxia (frataxin, not fragile X)
Covered
by MDA; others are generally not
Cardiomyopathy, diabetes, scoliosis
Unless family history positive for specific
gene,
Just say WES. (Just my $0.02)
16. TRANSITIONS
Adhalin = alpha sarcoglycan
SCARMD = sarcoglycanopathy or other LGMD2
High CPK with some dystrophin on biopsy ≠ Becker’s
In 2006 had six genes for dystroglycanopathy,
50% undiagnosed, now about 15 and fewer
Some conditions caused by more than one gene
Some genes cause more than one condition
Conditions vary with what is wrong with the gene
Some genes can cause disease as AR or AD
Conditions vary depending on other genes
What will we do when we run out of letters?
Only 6 more LGMDs to go…
17. CLASSIFICATIONS OF MUSCLE DISEASE
Congenital Myopathy
Congenital Muscular Dystrophy
Dystrophinopathy
EDMD
FSHMD
Limb Girdle
Collagen Related (Bethlem/Ullrich)
Dystroglycanopathy
Merosin-deficient and related
Rigid spine SEPN, Integrins, etc.
Dominant, recessive, distal
Myasthenia and myasthenic syndromes
18. EXAMPLE: LMNA
Nuclear envelope gene, aka Lamin A/C
Emery-Dreifuss muscular dystrophy
Scapuloperoneal, cardiac conduction concerns
EDMD 2 and 3, AD
(vs. SYNE1, SYNE2, FHL or x-linked with emerin)
LGMD1B AD “laminopathy”
CMT2B1 AR
p.R644C missense mutation in the lamin A/C protein
Familial partial lipodystrophy FPLD2 AD
Dilated cardiomyopathy CMD1A
Hutchinson-Gilford progeria
Due to farnesylated mutant prelamin A (progerin)
19. EXAMPLE: GLYCOSYLATION
BUILDING CROSSWALKS
LGMD2I = MDDGC5 = MDC1C (FKRP)
LGMD2K = MDDGC1 (POMT1)
LGMD2N = MDDGC2 (POMT2)
LGMD2O = MDDGC3 (POMGNT1)
LGMD2M = MDDGC4 (FKTN)
LGMD2P = MDDGC9 (DAG1)
LGMD2T = MDDGC14 (GMPPB) with/without ID, seizures
Japanese severe form of CMD
Compare with MDC1a, merosin aka alpha-laminin
We have one case – U of Iowa fibroblast culture rescue technique
Walker-Warburg can be several of the above
Santavuori (MEB) “cobblestone” usually POMgnT1
“Partial merosin-deficient” likely in this group (MDC1B,D,E or new)
CDGS
Classic with transferrin isoelectric focusing
Overlap with dystroclycanopathy (DPMs)
Brand new (PIGT) – we have two siblings, diagnosed by WES at NIH
21. LGMD & THE JAIN FOUNDATION TOOL
Primarily for LGMD2B, dysferlinopathy
Concept is to determine probability and concordance based
on clinical evaluation, FH, CPK, optionally biopsy and brain
MRI
They got 45/50 if first position, 3/7 if 2 or 3
A route to free 2B or 2I testing
Otherwise, great concept but does not quite work yet…
We got 1/12 specific (low concordance on a 2B)
We got 4/12 dystroglycanopathy non-specific
“definitively excluding conditions based on the presence or
absence of any one symptom isn't a good approach”
Working on it, adding Pompe, DYS carrier, etc.
Automated LGMD Diagnostic Assistant (ALDA)
http://jain-foundation.org/lgmd-subtyping-tool/content/login-tool
22. TWO “EASY” CASES
Young girl, brought in as affected DMD female due to
biopsy with abnormal dystrophin after high CPK
noted
Dystrophin gene normal
Phenotype merosin-deficient, confirmed genetically
Young man, looked like DMD
Dystrophin gene normal, CPK 8,000
Immunostaining with reduced c-terminal dystrophin,
COL6, alpha-dystroglycan, abnormal dysferlin and
caveolin pattern
Clinically not Bethlem-Ullrich, CNS near normal
Selected LGMD2 gene tests, 2I was positive
23. TWO “OTHER” CASES
Two girls, one more severely affected
Cataracts, club foot, intellectual disability
Carrying diagnosis of AMC
Genetics conference – consider DM1 vs WES
Whole exome indicates CMT 2O (dynamin)
Dynein defect reports more similar phenotype
but the two form a complex
Mom is low level mosaic
Edx (and publication?) pending…
24. THIS WENT RIGHT TO WES, RIGHTLY
Very severe Duchenne-like presentation
4 year old boy, weak from about 1 year of age,
progressing rapidly
CPK only 264, lactate/pyruvate 21./1.6
Biopsy “mixed myopathic” normal
immunostaining
WES had defect in thymidine kinase (TK2)
Autosomal recessive
Might also have been found in ROH on snp array
Mitochondrial DNA depletion, myopathic form
25. CONCLUSIONS
Single gene test if they walk in out of the textbook, or
known diagnosis in family
Non-genetic tests where helpful to narrow it down
Only a few of the panel tests make sense – ask Julie! –
could it really be ANY of the genes included?
SNP array, mito sequencing may be first step especially if
consanguinity or dysmorphism
WES if many possible categories, many possible genes,
panels more expensive
NIH seems better than Mayo if we are still stuck (Mayo
does not take AR Medicaid)
Genetics, genetic counselors, neuro, pathology, rehab
can all offer clues to differential diagnosis and
management – what would happen if we put our heads
together?
26. POST TEST (Easy – T/F)
Neuromuscular diagnosis should usually
include a CPK
Neuromuscular diagnosis should always
include electrodiagnosis and biopsy
Editor's Notes
Answers – not organized in an up to date way, and we now have AR LGMD up to 2T.(Yes, I did check to see if they had LGMD2U this morning – better check again shortly.)
Examples – only one of the sarcanoglycopathies has a clinical trial available in France; very different counseling for AR LGMD than Becker’s. Ryanodine receptor disorders highest risk for MH, Friedreich’s has DM, scoliosis, cardiomyopathy typically asymptomatic early on and is covered by MDA where other SCAs are not, FSH has risks of Coates-like retinopathy and hearing loss, but not cardiac; EDMD is very high risk for cardiac conduction problems.
AFP is for ataxia telangiectasia
Make sure what actually gets entered from your orders on these. Julie Kaylor (ACH genetic counselor position) will usually catch them and give you a call. Some flux in when a “good” panel is better than whole exome, may miss some items depending on company and technique, though whole exome is the only way to find genes not previously associated with human disease.
Good practice with panel testing – prices not hidden, groupings make sense.
These conditions are usually highly distinguishable from each other on a clinical basis. Myotonia with no other features of myotonic dystrophy should not be tested for that, and clinical Becker Thomsen-like cases would not be tested for DM1 or 2.
Probably go straight to WES for AMC if a specific diagnosis is needed. Sometimes in a classic sporadic case it may not be as critical.
This helps when reading older literature.DES gene can cause AD LGMD1e or myofibrillar disorder,but has just been shown to cause AR LGMD2r as well.
Another example is dystrophin, causing Duchenne, Becker, or in some cases cardiomyopathy only.
The more newly disocvered genes appear to cause either CMD with CNS anomalies, LGMD with, or LGMD without intellectual disability and may carry a modfier a, b, or c to indicate that.
Proteins may not stain normally if they are not in the right places with the proper connections. Glycosylation is apparently critical to correct assembly of the muscle tissue in several locations. Abnormalities of alpha-dystropglycan itself compatible with life are quite rare, and have not been found so far with beta-dystroglycan. The Golgi and ER associated genes in blue are involved in glycosylation and are the 6 identifed first as causing dystroglycanopathies. Reduced staining of dystrophin can be seen with abnormalities of the closely associated proteins, especially the dystroglycan complex as illustrated in the first case presented (2 slides down).
ALDA has problems in that answers vary wildly with changing just one item such as presence or absence of CNS structural abnormalities, and this is not necessarily accurate for the newer overlap LGMD/MDDGCs. Very easy to use though and worth registering for. Don’t worry about the YouTube video you cannot access from ACH. They love to hear from users and collect more information on how to try to improve this.
These girls had always used KAFOs – I was worried this had caused the remarkable degree of quadriceps weakness, but on getting this diagnosis it was more clearly part of this specific condition.
May not be any Rx, could try uridine supplementation, which has been helpful for a few lab mice.