Two cases, one gene

…a big one to consider with muscle disease and mild CPK elevatio

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Case 1: H&P• 14 year old male • Was a floppy, hypermobile term baby but improved, normal milestones• Fully mobile but not able to compete athletically• Occasional chest pain, breathing symptoms – heat, exertion, intermittent• Left neck and shoulder pain of increasing concern in softball, martial arts • ADD-inattentive sporadic treatment with Strattera, Concerta• FH negative, parents – dad no symptoms, mom mildly clumsy UEs

• Exam: – Very thin with limited muscle bulk, normal skin– Pectus excavatum– High arch but valgus, not varus on weightbearing– Mild ptosis, got worse, otherwise normal facial function, neck weakness– Hypoactive DTRs, especially quads, downgoing toes – Shoulder abduction 4-/5 R, 3-/5 L with L > R winging, biceps 4+ and triceps

4/5, forearms look larger in comparison (probably just normal).– Cannot heel walk. Toe walking developed over time though dorsiflexion also

weak, milder proximal weakness

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Case 1: Workup (Progressive, asymmetrical proximal > distal UE; distal > proximal LE), cardiopulmonary concerns

• CPKs 183, 294• Edx normal • Prior biopsy age 10 abnormal but considered nonspecific

– Small type 1 fibers– Irregular peripheral COL IV and decreased COL VI, no EM done

• PFTs declined over time • Cardiac studies

– EKG and ECHO normal at first – Holter after ER visit few PVC– After PFT decline noted, restudied and found dilated cardiomyopathy

with mildly diminished LV function, most recently SF 22%, EF 45% • Gene testing:

– Initially non-covered – FSHD studies negative

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Case 1: Considerations

• Scapuloperoneal? Congenital?– EDMD– TRPV4– Col VI

• Abnormal staining• Hypermobility• Scapuloperoneal rarely reported• Cardiac involvement not reported

– MYH7– FHL1– Others?

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Case 2: Presentation• 13 year old female

• Multiple admissions for malnutrition and pneumonia

• Scoliosis over 110 degrees and left eyelid droop

• Rough, dry skin

• CPK 74

• Parents wished to avoid interventions, but became concerned for GI malformations or other problems causing low appetite

• Found to have severe restrictive lung disease

• Needed tube feeds NGT and then GT feeds to gain any weight

• Used reverse walker for short distances only

• Posterior spinal fusion on 05/01/2018 after 4 months of halo gravity traction,

• Bilevel mode NIV16/6 plus airway clearance PR

• Treatment for osteoporosis

• Cardiac studies SF 29 %, EF 57 %.

• A single variant causing a stop codon was found on a neuromuscular panel.

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Case 1: Genetics• Free LGMD test – unable to get, unclear reasons

• Comp CMT negative, Comp MD:

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Case 1 and 2: Final Genetics

• Case1:

• By some miracle, WES trio coverage was obtained

• Mito sequence normal

• Revealed that the c.1970c>a in COL6A2, c965+5 g>t variant in TRAPPC11 both maternally inherited

• Maternally inherited c.102798_102800del TAA (p.Asn34266del) in TTN

• Paternally inherited c.63793g>a (p.Asp21265Asn) in TTN

• Case 2: Comp Myopathy

• c.8220g>a (p.Trp2740*) in TTN

• c.7433c>a (p.Thr2478Asn) in RYR1

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Titin – The largest protein• (Dystrophin is the largest gene)• 34,000 amino acids, 363 exons, one is 17,106 bases in length, all on 2q.31.2• Multiple isoforms, multiple interactions (actin, myosin, calpain, calmodulin, others)• Each molecule spans half a sarcomere (Z to M line) and is about 1 micron long• Flexibility, stretching, elasticity, structural stability • Domains (11 page exon chart)

– 244 individually folded domains, hinged or threaded together– IG like near Z-disk 1-28– I-band 29-44, 47, 50-130; PEVK 121-126 (proline, gluatamate, valine, lysine)– Unorganized areas and more of those through 252 – Novex 1, Novex 2, Novex 3 alternative splicing 45, 46,48– Some low cardiac expression areas, kinase domain for sensing – A-band 253-end fibronectin and Ig-like, less elastic to M band

http://www.uni-muenster.dehttp://slideplayer.com/slide/1707414/

Image from

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Titin Myopathies

• AD dilated cardiomyopathy 1g• AD familial hypertrophic cardiomyopathy 9• Muscular dystrophy, limb-girdle, autosomal recessive 10 (aka LGMD2j)

– Case 1• Myopathy, proximal, with early respiratory muscle involvement (AD HMERF)

– Case 2? - but commonly A150 (FN3 119) / ex344 • Salih myopathy, AR (severe fatal with cardiomyopathy, aka EOMFC) • Tardive tibial muscular dystrophy (AD) (Mex5-6, C-terminal – FINmaj, French, Iberian)• Young or early onset recessive tibial muscular dystrophy (Mex5-6, C-terminal)

– Case 1 • Centronuclear myopathy or multiminicore with cardiac involvement• EDMD-like without cardiac involvement • Atypical cases, mixed features

– Second mutations in cis in AD cases? – Compound heterozygotes

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Titin Myopathies – Variety of biopsy findings

• Mild variation in fiber size, type 1 predominance

• Abundant centrally located nuclei

• Dystrophic with endomysial fibrosis, fatty replacement

• Rimmed vacuoles – may be blue

• Myofibrillar – M-band, sarcomeric disruption

• Inclusion bodies positive for desmin, myotilin and valosin-containing protein, may be eosinophilic

• Mild reduction in calpain staining (greatest in tibial muscles)

• Titin immunostaining not applicable

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In conclusion• Other cases seen at UAMS and ACH

– Single VUS, pain in legs, negative biopsy – Tibial MD in adult

• TTN is a large gene, and though modern NGS will more frequently find some VUS not producing pathology, these should not be disregarded.

• Mutations are associated with a variety of pathologies and genotype-phenotype correlations may vary. – M-band distal dystrophy younger onset if recessive– Otherwise AD cases tend to be more severe

• Should be added to list of etiologies for scapuloperoneal phenotype with or without cardiac involvement and mild CPK elevation.

• Titin myopathies may not be as rare as we thought.

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References• Increasing Role of Titin Mutations in Neuromuscular Disorders, Marco

Savaresea, Jaakko Sarparantaa, Anna Viholaa, Bjarne Udd, Peter Hackman, Journal of Neuromuscular Diseases 3 (2016) 293–308

• The Kinase Domain of Titin Controls Muscle Gene Expression and Protein Turnover, Lange, Stephan; Fengqing Xiang; Yakovenko, Andrey; Vihola, Anna, et al, Science; Jun 10, 2005; 308, 5728; ProQuest

• Hereditary myopathy with early respiratory failure associated with a mutation in A-band titin, Monica Ohlsson, Carola Hedberg, Bjorn Bradvik, Christopher Lindberg, Homa Tajsharghi,Olof Danielsson,Atle Melberg Bjarne Udd, Tommy Martinsson, Anders Oldfors, Brain 2012: 135; 1682–1694

• Atypical Phenotypes in Titinopathies Explained by Second Titin Mutations, AnniEvila, Anna Vihola, Jaakko Sarparanta, Olayinka Raheem, Johanna Palmio, SatuSandell, MD, Bruno Eymard, MD, PhD, Isabel Illa, Ricard Rojas-Garcia, Karolina Hankiewicz, Luis Negrao,Tuija Lopponen, Pekka Nokelainen, Mikko Karpp, Sini Penttil, Mark Screen, Tiina Suominen, Isabelle Richard, Peter Hackman, Bjarne Udd. Ann Neurol 2014;75:230–240

• OMIM https://www.omim.org/entry/188840• Leiden http://databases.lovd.nl/shared/docs/TTN_splice.html• http://titinmyopathy.com/ for patients