Inborn Errors of Metabolism--Complex Molecules Flashcards by Keri Ramsey

What does the peroxisome do?

Carry out oxidation reactions which result in break down of fatty acids.

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What are the general features of peroxisomal disorders?

Elevated very long-chain fatty acids
Onset infant to adult
Dysmorphic features
Hypotonia
Liver disease
Seizures
Cognitive dysfunction

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What are the genes that cause Zellweger syndrome?

PEX genes (AR); PEX1 most common

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What is the blood test performed in Zellweger syndrome?

Very long-chain fatty acids

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What are the features of Zellweger syndrome?

Feeding difficulties
Hepatosplenomegaly
Dysmorphic features
Hypotonia
Seizures
Cognitive dysfunction
*Chondrodysplasia punctata (stippling near the ends of the bones)

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What is the gene responsible for X-linked Adrenoleukodystrophy?

ABCD1 (X-linked)

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What are the features of X-linked Adrenoleukodystrophy (childhood onset)?

loss of vision
learning disabilities
dysphagia (difficulty swallowing)
seizures
deafness
lack of coordination and balance
fatigue
intermittent vomiting
weight loss
lack of appetite
nausea
darkening of the skin
progressive dementia
muscle weakness
low blood glucose (blood sugar)
headaches in the morning

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What are the features of X-linked Adrenoleukodystrophy (adult onset)?

Adrenomyeloneuropathy
-a stiff gait when walking and bladder and bowel dysfunction.

The adrenal glands often fail to produce enough steroid (cortisol) in people who have ALD, causing Addison’s disease.

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What percentage of X-linked Adrenoleukodystrophy is childhood onset?

1/3 (4-8 years)

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What is the blood test for X-linked Adrenoleukodystrophy?

Very long-chain fatty acids

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What is a therapy option for X-linked Adrenoleukodystrophy?

Stem cell transplant–before onset of symptoms

Is on NBS for that reason

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What is the gene mutation in Gaucher?

GBA (AR)

Genotype/phenotype correlation

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What is the enzyme deficient in Gaucher?

Glucocerebrosidase

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What is the phenotype of Gaucher disease?

Splenomegaly (95%)
Hepatomegaly (87%)
Thrombocytopenia (50%)
Anemia (40%)
Bone marrow infiltration (38%)
Bone pain (27%)

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What are the unique features of Gaucher disease Type I?

Bone disease
Hepatosplenomegaly
No CNS symptoms

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What are the unique features of Gaucher disease Type 2?

CNS symptoms (seizures, brain damage), death by 4

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What are the unique features of Gaucher disease Type 3?

CNS symptoms
Slower progression
Survival into 20-30s

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What is the blood test for Gaucher disease?

Lyso-Gb1
Glucocerebrosidase enzyme testing

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What is the treatment for Gaucher disease?

Enzyme replacement
Substrate reduction

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What is the genetic cause of Fabry disease?

GLA (X-linked)

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What is the phenotype of Fabry disease?

*Pain in the hands and feet
Tickling and prickling
Burning
Kidney disease
Abnormal heart rhythms
Heart enlargement
Increased stroke risk
*Sweating abnormalities
*Cataracts
*Angiokeratoma (looks like a dark red wart)

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What enzyme is deficient in Fabry disease?

Alpha-galactosidase

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What is the blood test in Fabry disease?

Lyso GL3
Enzyme

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What is the therapy in Fabry disease?

Enzyme replacement (still some remaining organ damage)

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What is the genetic cause of Pompe disease?

GAA (AR)

What is the phenotype of Pompe disease (infantile)?

*First few months of life Hypertrophic cardiomyopathy (enlarged heart) Skeletal muscle weakness (diaphragm and other breathing muscles)

What is the phenotype of Pompe disease (juvenile and late-onset)?

*Any age Proximal limb weakness (shoulders and hips) Progressive diaphragm weakness (Breathing difficulties) *Heart NOT involved

What percentage of Pompe disease is juvenile/adult onset?

80%

What testing do you do for Pompe disease?

GAA gene testing Hex4 in the urine Enzyme testing

What is the treatment for Pompe disease?

Enzyme replacement

What is the phenotype of Niemann Pick C?

Childhood onset (~6 years) Clumsiness of gait Slurring of speech Cataplexy (strong expression of emotion) causes sudden weakness and loss of control of body Vertical gaze palsy (can't move eyes up) Liver disease Lung disease Progressive decline in cognitive function Psychiatric symptoms

What are the tests for Niemann-Pick Type C?

NPC1 and NPC2 gene testing Oxysterols

What is the treatment for Niemann-Pick Type C

Miglustat (oral drug, slows disease)

What is the testing in Krabbe disease?

GALC gene Psychosine

What is the treatment of Krabbe disease?

Hematopoietic stem cell transplant (before 2 wks old) Slows progression

What is the phenotype of Krabbe disease?

Death before 2 years Extreme irritability Spasticity Developmental delay

What is the phenotype of Tay-Sachs Disease?

Regression Seizures *Cherry red spots Death by 2 years

What testing is performed in Tay-Sachs?

HEXA enzyme testing preferred Urine oligosaccharides HEXA gene testing

What is the gene change in Sandhoff?

HEXB

What is the juvenile form of Neuronal Ceroid Lipofuscinoses?

Batten disease Many gene changes (CLN1, CLN2, CNL3, 4, 5...) (AR)

What is the phenotype of Batten disease (juvenile form of Neuronal Ceroid Lipofuscinoses)?

Progressive problems with vision, movement, and cognition

What accumulates in mucopolysaccharidoses (MPS)?

Excess glycosaminoglycans GAGS collect in cells, blood, and connective tissues which affects appearance (progressively coarsening features, skeletal abnormalities) and organ function (enlarged organs)

What is the phenotype in MPSI (Hurler syndrome)?

Most common MPS Corneal clouding Cognitive delay Coarse facial features

What is the gene change in MPSI (Hurler syndrome)?

IDUA (AR)

What is a distinctive phenotype in MPSII (Hunter syndrome)?

Progressive decline in cognitive function (late) *No corneal clouding

What is the gene change in MPSII (Hunter syndrome)?

IDS (X-linked)

What is a distinctive phenotype in MPSIII (Sanfilippo syndrome)?

CNS and behavioral symptoms Aggression Autism Social differences Sleep and movement disorders Hearing and vision problems No cardiac anomalies

What are the genes responsible for MPSIII (Sanfilippo syndrome)?

SGSH NAGLU HGSNAT GNS (AR)

What is the distinct phenotype in MPSIV (Morquio syndrome)?

Short trunked dwarfism (significant skeletal problems) Normal intelligence

What are the gene changes in MPSIV (Morquio syndrome)?

GALNS GLB1 (AR)

What testing do you perform when you suspect a Mucopolysaccharidoses (MPS)?

Urine glycosaminoglycans (GAGs) (aka urine mucopolysaccarides) Enzyme levels should be deficient

What are the treatments for Mucopolysaccharidoses (MPS)?

Enzyme replacement (none for MPSIII) MPSI -- Stem cell transplant

What are the general features of Glycogen Storage Disorders?

Enlarged liver Hypoglycemia (within 3-4 hours) Multiorgan involvement

What is a distinctive finding in Glycogen Storage Disorder Type I?

Elevated lactate

What do you give in Glycogen Storage Disorders to help with hypoglycemia?

Cornstarch (will increase the fasting period by a few hours) IV glucose with illness

What is the most common gene change in Glycogen Storage Disorders?

PMM2 (AR)

What test do you perform with Congenital Disorders of Glycosylation?

N-glycans O-glycans (doesn't tell you which protein is abnormal)

What is the gene change in Smith-Lemli-Opitz?

DHCR7 (AR)

What enzyme is deficient in Smith-Lemli-Opitz?

7-dehydrocholesterol reductase deficiency

What is the phenotype of Smith-Lemli-Opitz?

Cognitive impairment Growth restrictions Distinctive features *2-3 syndactyly genital abnormalities (underdeveloped male genitalia) Cardiac defects

What do you test in Smith-Lemli-Opitz?

7-dehydrocholesterol (elevated)

What genes cause Familial Hypercholesterolemia?

LDLR (most common) APOB PSCK9

What are the findings with Familial Hypercholesterolemia?

Atherosclerotic plaque development Xanthelasma around the eye (yellow fatty deposits) Tendon Xanthomas (yellow fatty deposits)

What is the genetic cause of Lysosomal Acid Lipase?

LIPA gene

What is the phenotype of Lysosomal Acid Lipase?

Significant liver damage from accumulation of cholesterol High LDL --> atherosclerosis, heart attacks, stroke Cells pick up cholesterol but can't break it down

What is the treatment of Lysosomal Acid Lipase?

Enzyme replacement therapy

What is the gene change in Cerebrotendinous Xanthomatosis?

CYP27A1

What is the phenotype of Cerebrotendinous Xanthomatosis?

Diarrhea in infancy Cataracts in childhood Xanthomas in young adult Neurological dysfunction in adult

What is the blood test for Cerebrotendinous Xanthomatosis?

Cholestanol

What is the treatment in Cerebrotendinous Xanthomatosis?

Chenodeoxycholic acid

What is Pseudodeficiency?

When an individual has markedly reduced enzyme activity but remains asymptomatic Clan have phenotype/genotype correlation

What are the disorders with Pseudodeficiency?

Fabry Pompe Krabbe Tay-Sachs/Sandhoff/GM2 Metachromatic leukodystrophy MPSI MPSII