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MedGen Part 2 > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What are the three key carbohydrate pathways?

A

galactose metabolism, fructose metabolism, glycogen metabolism

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2
Q

What two monomers is lactose made up of?

A

galactose + glucose

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3
Q

What is the name of the pathway responsible for galactose breakdown?

A

Leloir pathway

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4
Q

What are the three major enzymes involved in the Leloir pathway?

A

GALK1, GALT, GALE

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5
Q

What are the biochemical results of galactokinase deficiency?

A

low GALK
low Gal-1-P
high galactitol
normal GALT
high galactose concentration in blood and urine

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6
Q

What are the clinical symptoms of galactokinase deficiency?

A

Galactosemia type III
infantile cataracts

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7
Q

What are the biochemical results of GALT deficiency?

A

classic and partial variant depending on amount of residual enzyme
accumulation of galactitol and galactose/gal-1-P in blood/urine/red blood cells

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8
Q

What are the clinical symptoms of classical GALT deficiency?

A

Cataracts
Liver enlargement
Avoid lactose
Sepsis
Speech apraxia
ID/DD
Color (jaundice)
gonadal dysfunction (POI in females) and growth delay

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9
Q

What are the clinical symptoms of variant galactosemia?

A

African founder variant protective against POI
most frequent outcome of abnormal NBS for galactosemia
generally asymptomatic
debated whether dietary intervention is required

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10
Q

How is classical galactosemia treated?

A

lactose and galactose eliminated from diet
clinical monitoring with gal-1-p levels in erythrocytes

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11
Q

What are the biochemical results of GALE deficiency?

A

prevents formation of glucose-1-P
generalized: enzyme activity low in all tissues
peripheral: enzyme activity low in RBCs and WBCs only
Intermediate: enzyme activity low in RBCs and WBCs, and <50% of normal in other tissues

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12
Q

What are the clinical symptoms of GALE deficiency?

A

variable phenotype
generalized: hypotonia, poor feeding, vomiting, weight loss, jaundice, hepatomegaly, cataracts
peripheral: asymptomatic
intermediate: intermediate symptoms
treatment: primarily for generalized/intermediate

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13
Q

What two monomers make up sucrose?

A

fructose + glucose

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14
Q

Where does galactose metabolism occur?

A

liver

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15
Q

Where does fructose metabolism occur?

A

75% liver
20% kidneys
10% intestines

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16
Q

What is the key enzyme involved in fructose metabolism?

A

aldolase
Aldolase A- muscle
Aldolase B- liver
Aldolase C- brain

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17
Q

What’s a good way to remember fructokinase deficiency? Gene?

A

Fructo-kinda-ase deficiency
clinically benign
low fructokinase leads to high fructose in urine and blood
KHK gene

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18
Q

What are the biochemical results of hereditary fructose intolerance?

A

accumulation of fructose-1-P
impairs gluconeogenesis and glycogenolysis which require ATP

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19
Q

What are the clinical symptoms of hereditary fructose intolerance?

A

most common disorder of fructose metabolism
hypoglycemia + metabolic acidosis
acute: sweating, nausea/vomiting, lethargy –> coma/death
chronic: growth deficiency, FTT, abdominal distention, liver/kidney damage
ALDOB gene

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20
Q

When is hereditary fructose intolerance typically diagnosed?

A

switching from breast milk to formula

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21
Q

How is hereditary fructose intolerance treated?

A

fructose/sucrose in the diet is eliminated/reduced
follow-up of liver/kidney function

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22
Q

What are the biochemical results of fructose-1,6-bisphosphatase deficiency?

A

impaired formation of glucose from all gluconeogenic precursors

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23
Q

What are the clinical symptoms of fructose-1,6-bisophosphatase deficiency? Gene?

A

hypoglycemia when glycogen is limited
metabolic acidosis: hyperventilation, shock, lethargy, convulsions, coma/death
FBP1 gene

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24
Q

How is fructose-1,6-bisphosphatase deficiency treated?

A

avoid fasting and provide exogenous glucose to maintain BG levels (e.g. cornstarch)

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25
What are the two types of GSD I?
Ia: G6Pase deficiency caused by pathogenic variants in G6PC gene Ib: G6Pase transporter deficiency caused by pathogenic variants in SLC37A4 gene
26
What two processes do GSDs interrupt?
glycogenolysis and gluconeogenesis
27
When is GSD I often diagnosed?
in infancy when baby starts sleeping through the night
28
What are the clinical symptoms of GSD I?
initially: hepatomegaly, delayed growth, FTT, seizures, lactic acidosis other symptoms: doll-like facies, hyperlipidemia, impaired platelet function, neutropenia and impaired neutrophil dysfunction (type Ib only), kidney failure, hepatic adenomas, gout, osteoporosis
29
What is the treatment for GSD I?
prevent hypoglycemia with frequent feeds/cornstarch therapy kidney or liver transplant in some cases Type Ib: granulocyte colony-stimulating factor for WBCs
30
What are the steps of lyososomal enzyme movement?
1. generated in ER 2. transported to Golgi and tagged with mannose-6-phosphate (M6P) critical for localizing to lysosome 3. M6p receptors on cell membrane bind to M6P
31
What are the three mechanisms of lysosomal storage diseases?
1. not enough enzyme or enzyme that doesn't work properly 2. failure of lysosomal transport/enzyme localization 3. enzyme structure is altered such that it cannot be identified as an enzyme and localize
32
What type of enzymes bring about most lysosomal storage diseases?
sugar hydrolases
33
What is the function of sugar hydrolases?
degrade complex carbs like glycoproteins (carb + protein), glycolipids (carb + lipid), and glycosaminoglycans (GAG) (essentially glycoproteins)
34
What lysosomal storage diseases are X-linked?
Hunter syndrome (MPS) and Fabry disease
35
What are other names for Pompe disease?
GSD II, acid maltase deficiency, GAA deficiency
36
What GSD is also an LSD?
GSD II!!! Pompe disease
37
What are the biochemical results of Pompe disease?
deficiency of alpha-1,4-glucosidase (GAA or acid maltase) buildup of glycogen results in tissue damage (primarily muscle)
38
What are the two types of Pompe diseases and what are their respective characteristics?
Infantile-onset: significantly reduced GAA levels; HCM, FTT, rapidly progressing muscle weakness, respiratory failure, aspiration, developmental delay; death by 1-2 years if not treated Late-onset: some enzyme activity; more slowly progressive muscle weakness and absence of HCM in 1st year; proximal muscles and trunk must affected; can have cardiac rhythm disturbances and respiratory dysfunction
39
What are the treatments for Pompe disease?
ERT symptomatic, supportive therapies immediate treatment is necessary for infantile-onset, for those with late-onset treatment start will vary with symptoms
40
What kind of condition is Gaucher disease?
sphingolipidosis (fat and carb)
41
Where are manifestations of Gaucher disease primarily seen?
bone, liver, and spleen
42
What is the etiology of Gaucher disease?
deficient glucocerebrosidase involved in breakdown of glycolipids glycosylceramide and glucosylsphingosine builds up in macrophages
43
What are the three types of Gaucher disease?
Type 1-non-neuronopathic (chronic-most common) Type 2-neuronopathic (acute-extremely rare-infantile) Type 3-neuronopathic (sub-acute/chronic-juvenile)
44
There is clinical overlap between Gaucher disease and what disease?
Niemann Pick (acid sphingomyelinase deficiency/ASMD) SMPD1 higher frequency of lung involvement, liver disease, cardiac disease, and dyslipidemia
45
What are the clinical symptoms of Gaucher disease type 1?
onset: childhood-adulthood visceromegaly, thrombocytopenia and/or anemia (bleeding gums), multiple myeloma, growth restriction, bone/joint pain, NO CNS involvement
46
What are the clinical symptoms of Gaucher disease type 2?
onset: 3-6 months rapidly progressive CNS degeneration around 6 months death from pulmonary and neurologic disease occurs by 2 years hepatosplenomegaly
47
What are the clinical symptoms of Gaucher disease type 3?
hepatosplenomegaly first CNS deterioration more slowly progressive Age of onset variable-many live into young adulthood skeletal involvement may be debilitating
48
Pathogenic variants in what gene are responsible for Gaucher disease?
GBA
49
What treatments are available for Gaucher disease?
enzyme replacement therapy, substrate reduction therapy, blood transfusions, pain management, total or partial splenectomy
50
What gene is associated with Fabry disease? etiology?
GLA deficiency of alpha-galactosidase A
51
What ocular finding is pathognomonic for Fabry disease?
wheel and spoke pattern (corneal opacity)
52
What gene is associated with Krabbe disease? etiology?
GALC deficiency of beta-galactosidase causing accumulation of galactocerebroside accumulation results in destruction of myelin
53
What are the clinical symptoms of Krabbe disease?
infantile: fatal in the first few months of life; paralysis, seizures, blindness, deafness "crabby" babies later-onset form: neurologic features appear by 10-12 years; vision loss, hypertonia, difficulty walking, cognitive impairment, shortened life span
54
What category of diseases does Tay Sachs fall into?
GM2 Gangliosidoses along with Sandhoff disease
55
Biochemically, how are Tay Sachs and gangliosidoses differentiated?
Tay Sachs: deficiency of hex A Sandhoff disease: both enzymes affected
56
What are the primary clinical symptoms associated with infantile-onset GM2 gangliosidoses?
rapid, progressive CNS degeneration infants usually never walk and have feeding problems, blindness, deafness, and convulsions Death at 2-3 years macular red cherry spot
57
What is the biomarker for MPS?
urinary excretion of GAGs
58
What are the types of GAGs involved in MPS?
Dermatan sulfate (DS): visceral and bone involvement Heparan sulfate (HS): CNS involvement Keratan sulfate (KS): bone involvement (flattening of vertebral bodies)
59
What are the forms of MPS I?
Severe - Hurler syndrome Intermediate - Hurler-Scheie syndrome Mild - Scheie syndrome
60
What is the treatment for MPS I?
ERT approved in 2003
61
What triad is seen in MPS I?
DD, hearing loss, and macroglossia
62
What are the major differences between MPS I and II?
MPS II has X-linked recessive inheritance and no corneal clouding
63
Which MPS is Sanfilippo syndrome?
MPS III

MedGen Part 2 (15 decks)

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