mitochondrial disease...

MITOCHONDRIAL DISEASE PRIMER

Amel Karaa, MD

Director of the Mitochondrial Disease Program

Massachusetts General Hospital

Disclosures & Disclaimers

• UMDF fellow, SMAB member.

• North American Mitochondrial Disease Consortium site PI.

• Advisory Board of the Mitochondrial Medicine Society and MitoAction.

• Grants and research support from Stealth BioTherapeutics, Reata pharmaceuticles, Sanofi Genzyme, Shire, Portalix.

• Consulting for Sanofi Genzyme, Stealth Biotherapeutics, Alexion, Lumleian, Homology, MitoBridge, Akros, Astellas.

Cases • 8 mo female with jaundice and liver failure

• 3 yo male with developmental regression and seizures

• 15 yo female with migraines, severe constipation, fainting

• 24 yo male with speech and balance problems

• 30 yo female with enlarged heart and strokes

• 55 yo male with weakness, muscle pain, hearing loss

• 71 yo female with dementia, diabetes, jerking limbs

• Overview of the mitochondria

• Overview of mitochondrial function

• Overview of mitochondrial genetics

• Overview of mitochondrial disease

Outline:

Overview: The mitochondria

http://biology.tutorvista.com/animal-and-plant-cells/mitochondria.html

Overview: the mitochondria

1 to 1000s/cell


What does mitochondria do?

Overview: the mitochondrial function

Trends in Pharmacological Sciences 2012 33, 341-352DOI: (10.1016/j.tips.2012.03.010)


http://www.bio.davidson.edu/

Nat Rev Genet. 2012 December ; 13(12): 878–890


The electron transport chain


Cell Metabolism 2009 9, 1-3DOI: (10.1016/j.cmet.2008.12.011)


Christian A. Wurm et al. PNAS 2011;108:13546-13551


Vafai et al. Nature 2013:491, 374–383


Vafai et al. Nature 2013:491, 374–383

https://www.bbe.caltech.edu


The unique genetics


mtDNA nDNA

The Mitochondrial

Organelle

Bi-genomic Input

http://images.google.com/imgres?imgurl=http://www.nlm.nih.gov/MEDLINEPLUS/ency/images/ency/fullsize/8770.jpg&imgrefurl=http://www.nlm.nih.gov/MEDLINEPLUS/ency/imagepages/8770.htm&usg=__XfYxaNHjXcTJxcvffPghRpEsASE=&h=320&w=400&sz=13&hl=en&start=5&tbnid=8DCYulUcWzVnoM:&tbnh=99&tbnw=124&prev=/images?q=chromosomes&gbv=2&hl=en

Nat Rev Genet. 2012 December ; 13(12): 878–890

Overview: the mitochondria The electron transport chain

Science, VOL 349 ISSUE 6255

Overview of nDNA

Polymerase Gamma (POLG)

https://tools.niehs.nih.gov/polg/

Gorman et al. Nature reviews primers 2016

Overview of nDNA

http://www.slideshare.net/

Sporadic/De novo

Overview of mtDNA

16,569 bp

Encodes 37 proteins:

22 tRNAs

13 respiratory chain peptides

2 ribosomal

10s copies/mitochondrion, 100–1000s/cell

Limited DNA repair (↑mutation rate)

• Maternal inheritance

Overview of mtDNA

Point mutations Deletions/Duplications

Point mutations Deletions/Duplications Depeletion

Overview of mtDNA

• MELAS: Mitochondrial Encephalomyopathy, Lactic

Acidosis and Strokes

• MERRF: Myoclonic Epilepsy with Ragged Red Fibers

• LHON: Leber’s Hereditary Optic Neuropathy

• NARP: Neuropathy, ataxia and retinitis pigmentosa

• KSS/PEO: Kearns Sayre syndrome/Progressive

external ophthalmoplegia.

Courtesy of Dr. Michio Hirano

• 1:200 people have an mtDNA mutation*

• Random segregation

• Threshold expression

• Heteroplasmy

Overview of mtDNA

* Chinnery et al 2008

Overview of mtDNA

http://clinicalgate.com/the-human-microbiome/

Overview of mtDNA

jcb.rupress.org

• Primary Mitochondrial Disease

Vs.

• Secondary Mitochondrial Dysfunction

Overview of mitochondrial disease

Annals of Medicine, 2013; 45: 4–16

http://www.amdf.org.au/mito-info.htm

• Lates accepted prevalence is 1 in 4,300*


* Skladal et al, Brain 126, 1905–1912 (2003).



• Any age – infancy to adulthood

• Multi-organ dysfunction

• Variable severity

• Progressive


An extraordinary clinical spectrum of mitochondrial

diseases:

- underdiagnosed "What is this complex disorder?“

- over diagnosed "This disorder is so complex that is

must be mitochondrial!".


• When should I suspect mitochondrial disease

‘…any organ, any symptom, any age’


• Red flag symptoms

http://www.mitosoc.org/toolkit/


http://www.stlukeseye.com/conditions/RetinitisPigmentosa.html

http://www.mitosoc.org/toolkit/

0 10 20 30 40 50 (%) 0 10 20 30 (%)

Encephalopathy Myopathy

Myocardiopathy

Exercise intolerance

Kidney disease

Leigh syndrome

Ophthalmoplegia

Intestinal disease

Dysmorphy Bone marrow dysfunction

Retinopathy

Peripheral neuropathy Ataxia

MERRF/MELAS Deafness

Alpers syndrome

Diabetes

Optic atrophy

Liver disease

Adults (n = 390) Children (n = 220)

SIMD/NAMA :Courtesy of Dr A Lombes Hopital La SalpétrièreUniversité Paris VI


Most common reasons for referral

Children Adults

Hypotonia

Seizures

Developmental delay

Elevated lactate levels

Abnormal MRI images

Liver disease

Failure to thrive

GI dysmotility

Fatigue +++

Shortness of breath, air hunger

Muscle pain

GI dysmotility

Dysautonomia/POTS

Multiple symptoms in many organ

system that do not seem to be related


Episodic Phenotype

TIME

OBSERVABLE

DYSFUNCTION

normal

aging mild

severe

moderate Organ

Failure

Metabolic Stress


Diagnostic Evaluation: The problem

• Nonspecific symptoms

• There is no universally accepted diagnostic algorithm for

mitochondrial disorders

• There is no gold standard diagnostic method.

• Enzyme (ETC) testing may produce false positive and

false negative results.

• Molecular testing is positive in 25-45% of the cases at

best.

NEUROLOGY 2006;67:1823–1826

Diagnostic Evaluation IMAGING TESTING

Leigh MELAS KSS ETC def MNGIE MERRF – Bilateral deep gray [putamen, GP, caudate]

– Metabolic stroke [non-vascular territory]

– Diffuse white matter abnormalities

– Lactate on MRS (abnl choline, NAA)

– Cerebral and/or cerebellar volume loss E.Grant

Diagnostic Evaluation

EM

RRF

Histochemistry

COX SDH

Molecular Testing: New Gold standard

• mtDNA

• Screen point mutations

• Whole genome screen

• Deletion/duplication analysis

• Depletion


Molecular Testing: New Gold standard

• mtDNA • Screen point mutations • Whole genome screen

• Deletion/duplication analysis

• Depletion

• nDNA • Specific gene selection

• Screening – NGS

panel

whole exome/whole genome or dual genome analysis


Biomarkers • FGF21

• DGF15

The Management

• Symptomatic

• End organ survey and treatment

• Supportive

• Overall disease burden

• Non curative

Minimize

energy

losses

Optimize

energy

gains

Typical treatment: Symptomatic

Avoid dehydration

Electrolyte abnormalities

Nutrition (enteral vs. parenteral)

Special formulas/diets

GT/JT

Annual Cardiologist exam

(KSS)

Prophylactic pacemakers

Annual Neurology exam

Avoid valproic acid

MRI, EEG, EMG

Annual ophtho exam

Prisms, slings

Blepharoplasty

Annual screen

AFT

Hearing evaluation

Sleep disturbances and

apnea, polysomnography

Nature Cell Biology 7, 853 (2005)

Treatment and Management

Exercise

Typical treatment: Supportive

• Hydration

• Diet adjustments


• Palliative Care Team

• Early Intervention

• Social worker, case manager

• Support Groups, etc.

• Avoid environmental toxins:

• ETOH

• Smoking

• Certain medications


Episodic Phenotype

TIME

OBSERVABLE

DYSFUNCTION

normal

aging mild

severe

moderate Organ

Failure

Stress

• Avoid physiologic stressors:

Infection (treat early, control fevers)

Heat (hydration, cooling vest, avoidance)

Fasting (minimize)

Lack of sleep

Typical treatment

• Dietary Supplements (The Mito Cocktail)

What makes sense?

Typical treatment

Mitochondrial replacement therapy


Ressources

• Thank you, and any questions?

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mitochondrial disease...

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