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Medical Genetics I > Mitochondrial Disorders Pt. 2 > Flashcards

Mitochondrial Disorders Pt. 2 Flashcards

1
Q

1 in ___ children in the US will develop mito disease by the age of 10y

A

4000

Note: the more severe, the earlier it presents, there is no precise data for adult incidence

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2
Q

What should raise suspicions for mito disease?

A

Involvement of 3 or more organ systems

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3
Q

Mito diseases are ___ and ___

A

Progressive, multisystemic

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4
Q

Mito disease w/ prominent muscular problems

A

Mitochondrial Myopathy

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5
Q

Mito disease w/ both muscular and neuro problems

A

Mitochondrial encephalomyopathy

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6
Q

When should you suspect mito disease?

A

Wide spectrum of symptoms and signs in an individual patient

Note: any symptom in any organ at any age

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7
Q

Why is mito disease a difficult dx?

A

Absence of reliable screening or diagnostic biomarker that is both sensitive and specific in all cases of mito disease

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8
Q

Name 9 neuro red-flags in mito disease

A
  • Cerebral stroke-like lesions in a nonvascular pattern
  • Basal ganglia disease
  • Encephalopathy
  • Neurodegeneration
  • Epilepsia partialis continua (intractable epilepsy)
  • Myoclonus
  • Ataxia
  • MRI findings consistent w/ Leigh disease
  • Characteristic MRS peaks
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9
Q

What is cerebral stroke-like lesions in a nonvascular pattern associated with?

A

Mitochondrial encephalopathy lactic acidosis (MELAS)

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10
Q

What is basal ganglia disease associated with?

A

LEIGH syndrome

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11
Q

What is myoclonus associated with?

A

Mitochondrial Encephalopathy Ragged Red Fibers (MERRF)

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12
Q

What is ataxia associated with?

A

Neurogenic ataxia-retinitis pigmentosa (NARP)

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13
Q

Name 5 cardio red-flags in mito disease

A
  • HCM w/ rhythm disturbance
  • unexplained heart block in a child
  • CM w/ lactic acidosis (>5 mM)
  • DCM w/ muscle weakness
  • Wolff-Parkinson-White arrhythmia
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14
Q

Name 5 ophthalmologic red-flags in mito disease

A
  • retinal degeneration w/ signs of night blindness, color-vision deficits, decreased visual acuity, or pigmentary retinopathy
  • ophthalmoplegia/paresis: unable to move eyes
  • fluctuating, dysconjugate eye movements: roving eyes
  • ptosis: droopy eyelids
  • sudden- or insidious-onset optic neuropathy/atrophy: sudden blindness
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15
Q

Name 3 GI red-flags in mito disease

A
  • unexplained or valproate-induced liver failure
  • severe dysmotility: severe constipation
  • pseudo-obstructive episodes: intestinal obstruction/non-surgical

Note: valproate is a common seizure/depression drug

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16
Q

Name 4 other red-flags in mito disease (not neuro, cardio, opthalmological, or GI)

A
  • unexplained hypotonia, weakness, FTT and metabolic acidosis (e.g. lactic acidosis) in a newborn, infant, or young child
  • exercise intolerance that is not in proportion to weakness
  • hypersensitivity to general anesthesia
  • episodes of acute rhabdomyolysis: high CK, muscle breakdown
17
Q

Describe myopathy

A
  • Muscle weakness and wasting
  • Exercise intolerance
  • Weakness/wasting in face and neck lead to slurred speech and dysphagia
18
Q

Describe exercise intolerance

A
  • Unusual feeling of exhaustion brought on by physical exertion
  • Spectrum of severity
  • Sometimes associated w/ muscle cramps and/or injury-induced pain
19
Q

What can occur if someone who has exercise intolerance “overdoes it”?

A

Cramps, Rhabdomyolysis

Note: this can occur during or after the overexertion

20
Q

What symptoms are associated w/ encephalomyopathy and how can they be managed?

A
  • hearing impairment –> managed using hearing aids and alternate forms of communication
  • migraine-like headaches –> alleviated w/ medications
  • Seizures –> preventative medications/anti-epileptics
  • Strokes –> arginine can be used for stroke-like episodes
    Note: variability in type and severity
21
Q

What are the characteristics of mito disease in older children and young adults?

A
  • later-onset –> chronic course
  • isolated myopathic and/or CM presentations, frequently w/ exercise intolerance, are common
  • fibromyalgia or chronic fatigue syndrome
  • sometimes rapidly progressive disease course w/ sudden regression –> often associated w/ physiologic stressor (viral/bacterial infection, severe illness, pregnancy and delivery, surgery)
22
Q

What are the characteristics of mito disease in older folks?

A

Regression manifested as:

  • nonvascular stroke
  • ophthalmoplegia
  • visual decline
  • mental status changes
  • array of new neurologic complaints
  • worsening exercise intolerance and fatigue
23
Q

True or false: the first episode of metabolic stroke in MELAS or metabolic encephalopathy in Leigh disease may be fatal at any age

A

True

24
Q

True or false: there is a definitive biomarker to diagnose mito disease

A

False

Note: lactic acidosis is neither sensitive nor specific

25
Q

Diagnosis of mito disease can be done by these 3 methods

A
  • identification of a pathogenic mtDNA or nDNA mutation via sequencing
  • tissue-biopsy evidence of abnormal electron-transport chain enzyme activity or impaired respiratory capacity
  • invasive procedures such as muscle or liver biopsy to obtain tissue for testing in specialized labs
26
Q

Who should you refer a patient to if symptoms and signs strongly suggest mito disease?

A

Metabolic specialist

27
Q

What baseline screening tests should be ordered for suspected mito disease?

A
  • basic chemistry –> is there acidosis
  • liver enzymes and ammonia –> how is the liver
  • CK –> measure of muscle breakdown
  • blood lactate, pyruvate, and lactate/pyruvate ratio
  • CBC
  • quant plasma AAs
  • quant urine organic acids
  • plasma acylcarnitine analysis
  • routine CSF studies (cell count, glucose, protein measurement, CSF lactate, amino acids)
28
Q

What other evals are beneficial to order in suspected mito disease?

A
  • ophthalmology
  • audiology
  • EKG and Echo
  • child neuro consult
  • genetics consult
29
Q

True or false: a normal lactate rules out mito disease

A

False

Note: even when plasma levels of lactate and pyruvate are normal, CSF lactate levels might be elevated; lactate might only rise during episodes of metabolic decompensation

30
Q

Which mito diseases frequently occur w/ minimal to no rise in lactate?

A
  • Leigh disease
  • Kearns-Sayre syndrome
  • Leber hereditary optic neuropathy
  • Mitochondrial polymerase-associated diseases
31
Q

What is a risk of a patient who experiences repeated “bad days”?

A

Often leads to decompensation and difficulty returning to baseline

32
Q

What can lead to a missed mito disease dx?

A
  • lack of understanding of disease
  • misinterpretation of symtoms
  • teenagers can be thought to be exaggerating or malingering
  • older pts can be thought to be malingering or mentally unstable

Note: misdiagnosis can lead to further progression of symptoms w/ missed opportunities for treatment and support

33
Q

What is the prognosis for people with mito disease?

A

Variable and unpredictable –> some people live a normal life and are minimally affected while other are severely compromised

34
Q

True or False: Prenatal testing is available for all types of mito disease

A

False

35
Q

Name 5 outcomes of mito disease

A
  • life threatening/life limiting
  • more severe in children
  • can cause little disability if person has enough functional mitochondria
  • no cure
  • supportive care
  • illness management
36
Q

What are the origins of mtDNA mutations?

A
  • damage to DNA: environmental factors, endogenous oxidative stress
  • spontaneous errors: DNA replication, translation synthesis, DNA repair re-synthesis

Medical Genetics I (18 decks)

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