1. A Novel Mitochondrial Metabolic Myopathy (mtMM) Caused by Variant Mitochondrial DNA
Michael M. Rothkopf, MD, FACN, Lisa Haverstick, RD, Eleni Pellazgu, MSN, APN
Metabolic Medicine Center
and
Darius Adams, MD, Personalized Genomic Medicine
Genetics and Metabolism,
Goryeb Children's Hospital
Atlantic Health System, Morristown, NJ
National Board of Physician Nutrition Specialists

2. Case Report: AR – 26 year old male
Referred from PCP for episodic rhabdomyolysis with persistent creatine kinase (CK) elevation
Has experienced collapse with severe exertion
On no meds or supplements
Does not drink or use recreation drugs
Otherwise fit and asymptomatic
Physical exam completely normal

3. Laboratory and Imaging Studies
Mild hepatic dysfunction (AST = 72/ALT = 71)
Mild renal dysfunction (Creat = 1.3; eGFR = 76)
CK = 1712 U/L (nl ), 100% CK-MM
Serum myoglobin = 277 ng/ml (nl 28-72)
HbA1C = 5.8% (nl <5.7)
Carnitine and micronutrient levels normal
MRI of both thighs – no myositis or atrophy.

5. Metabolic Myopathies (MM)
A group of hereditary muscle disorders caused by specific enzymatic defects.
Most considered primary inborn errors of metabolism (IEOM) and are associated with disturbances of intracellular energy metabolism.
MM diseases are grouped into abnormalities of glycogen, lipid, purine, or mitochondrial biochemistry.
Also grouped by symptomatology: dynamic vs static
Metabolic myopathies are rare but potentially treatable disorders. They are sometimes misdiagnosed as muscular dystrophies or inflammatory myopathies.

6. Rhabdomyolysis-associated MM
Disorders of Carbohydrate Metabolism
Myophosphorylase deficiency (GSD V;McArdle’s)
Phorphorylase kinase deficiency (GSD IX)
Phosphofructokinase deficiency (GSD VII: Tauri)
acid alpha-glucosidase (GSD II; Pompe)
Phosphoglycerate kinase deficiency
Phosphoglycerate mutase deficiency
Lactate dehydrogenase deficiency
Aldolase A (GSD XII)
β-enolase (GSD XIII)
Disorders of Lipid Metabolism
Carnitine Palmitoyltransferase Deficiency (CPT I/II)
Carnitine deficiency
Defects of beta-oxidation enzymes
Neutral Lipid Storage Disease
Lipin-1 deficiency
Disorders of Purine Metabolism
Myoadenylate deaminase (MADA) deficiency; erythrocyte, liver, muscle subtypes
Other Defects
Malignant hyperthermia
Alpha-methylacyl-CoQ recemase (AMACR) deficiency
Calcium adenosine triphosphates deficiency (Brody)
Mitochondrial Disorders

7. Differential diagnosis

8. Symptomatic Classification of MMs

10. Mitochondrial Metabolic Myopthy - mtMM
Mitochondrial DNA disease phenotypes are typically multisystemic
Muscle, CNS, PNS, hepatic, GI, other tissues.
Myopathy often involves key enzymes of energy metabolism
Can cause disease early in life
Mild cases may go unrecognized into adulthood

11. Mitochondrial Structure

12. ATP Production from Substrate

13. Oxidative Phosphorylation
Lets make this background slide 2
Lets start with metabolic myopathies: CPT1/2, McArdles, GSDs, other IEOMs, MM
Defects in the enzymes of oxidative phosphorylation effect all types of substrate utilization (glucose, fatty acids, amino acids)

14. Mitochondrial DNA (mtDNA)
Find circular image
Only organelle other than nucleus with its own DNA
Different structure than nuclear DNA - circular

15. Genes & Functions mtDNA encodes for 37 genes Peptides rRNAs: 2
Encodes 13 of mitochondrial peptide subunits
All 13 peptides are in mitochondrial respiratory-chain complex (OXPHOS)
Remaining > 67 OXPHOS subunits are nuclear encoded
rRNAs: 2
tRNAs: 22; Located between every 2 rRNA or Protein coding genes
Non coding region: Triple stranded (D) displacement-loop
Produced from additional synthesis of a piece of mitochondrial DNA, 7s DNA
Contains promoter region
Origins of replication for H and L strand replication
Contains elements for initiation of leading strand replication

16. Find circular image

17. Mitochondrial DNA variation
Homoplasmy; All copies of mtDNA are identical within cells
Heteroplasmy: Cells contain varied mtDNA populations
Occurs with some mtDNA mutations
Due to presence of multiple mitochondria in one cell, each containing several mtDNA copies
Produces tissue variation
Post-mitotic tissues
Usually contain highest levels of mutated mtDNA
Neurons; Skeletal & Cardiac muscle; Endocrine tissue
Mutations in mtDNA
% vs normal in mtDNA can vary among tissues in an individual
Mutational loads may change over time
Tissues are differentially sensitive to levels of mtDNA mutations: ? Related to oxidative energy requirements

18. Inheritance of mtDNA Maternal (ovum)
Paternal (sperm) mtDNA actively degraded
Maternal mtDNA mutations can be amplified by the “bottleneck effect” of primary oocytes

19. Case AR – Nuclear DNA Studies
Otherwise healthy 26 yo male with mild hepatic and renal dysfunction; persistent ↑CK/myoglobin
Rhabdomyolysis genetic sequencing screen (Baylor/Miraca) - no known pathologic variants in 27 MM nuclear genes

20. Case AR – mtDNA Genome
Mitochondrial genome submitted and compared to the MITOMAP database
Homoplasmic variant in cytochrome c oxidase (COX) subunit III (mt-CO3) gene found at position 9696 in which cytosine was substituted for thymine
Pathologic variant encodes a defective COX III protein - phenylalanine substituted leucine at position 164
Patient’s mother shares the variant, without apparent symptoms

22. Cytochrome c Oxidase (COX) subunit III

23. COX III Abnormality at Position 164 (L164F) - Phenylalanine Substitutes Leucine

24. Assessment
We suspected MM clinically on the basis of persistent CK and myoglobin elevations
We used a diagnostic algorithm and nuclear DNA testing to eliminate abnormalities of glycogen, lipid and purine biochemistry
We then proceeded with mitochondrial DNA sequencing to reveal a genetic defect in COXIII

25. Management and Follow-up
Complex carbohydrate, high protein diet
Careful attention to fluid intake to reduce the impact of myoglobin on renal function
Patient instructed to avoid heavy exertion
CK, myoglobin, liver enzymes and renal function have improved with this approach
Supplemental coQ10, creatine and alpha lipoic acid supplementation may be considered

26. Discussion/Conclusions
The patient’s rhabdomyolysis is apparently due to defect in OXPHOS caused by a pathologic variant in the gene encoding his COXIII.
He is clinically stable unless he undergoes extreme exertion.
He has no evidence of neurological, ophthalmologic or cardiac dysfunction but hepatic, renal and endocrine systems may be compromised.
This condition appears to represent a novel MM due to a maternally inherited pathologic variant in mtDNA.

27. Thank You for Your Kind Attention!