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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
Q

What are the two types of GSD I?

A

Ia: G6Pase deficiency caused by pathogenic variants in G6PC gene
Ib: G6Pase transporter deficiency caused by pathogenic variants in SLC37A4 gene

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26
Q

What two processes do GSDs interrupt?

A

glycogenolysis and gluconeogenesis

27
Q

When is GSD I often diagnosed?

A

in infancy when baby starts sleeping through the night

28
Q

What are the clinical symptoms of GSD I?

A

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
Q

What is the treatment for GSD I?

A

prevent hypoglycemia with frequent feeds/cornstarch therapy
kidney or liver transplant in some cases
Type Ib: granulocyte colony-stimulating factor for WBCs

30
Q

What are the steps of lyososomal enzyme movement?

A
  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
Q

What are the three mechanisms of lysosomal storage diseases?

A
  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
Q

What type of enzymes bring about most lysosomal storage diseases?

A

sugar hydrolases

33
Q

What is the function of sugar hydrolases?

A

degrade complex carbs like glycoproteins (carb + protein), glycolipids (carb + lipid), and glycosaminoglycans (GAG) (essentially glycoproteins)

34
Q

What lysosomal storage diseases are X-linked?

A

Hunter syndrome (MPS) and Fabry disease

35
Q

What are other names for Pompe disease?

A

GSD II, acid maltase deficiency, GAA deficiency

36
Q

What GSD is also an LSD?

A

GSD II!!! Pompe disease

37
Q

What are the biochemical results of Pompe disease?

A

deficiency of alpha-1,4-glucosidase (GAA or acid maltase)
buildup of glycogen results in tissue damage (primarily muscle)

38
Q

What are the two types of Pompe diseases and what are their respective characteristics?

A

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
Q

What are the treatments for Pompe disease?

A

ERT
symptomatic, supportive therapies
immediate treatment is necessary for infantile-onset, for those with late-onset treatment start will vary with symptoms

40
Q

What kind of condition is Gaucher disease?

A

sphingolipidosis (fat and carb)

41
Q

Where are manifestations of Gaucher disease primarily seen?

A

bone, liver, and spleen

42
Q

What is the etiology of Gaucher disease?

A

deficient glucocerebrosidase involved in breakdown of glycolipids
glycosylceramide and glucosylsphingosine builds up in macrophages

43
Q

What are the three types of Gaucher disease?

A

Type 1-non-neuronopathic (chronic-most common)
Type 2-neuronopathic (acute-extremely rare-infantile)
Type 3-neuronopathic (sub-acute/chronic-juvenile)

44
Q

There is clinical overlap between Gaucher disease and what disease?

A

Niemann Pick (acid sphingomyelinase deficiency/ASMD)
SMPD1
higher frequency of lung involvement, liver disease, cardiac disease, and dyslipidemia

45
Q

What are the clinical symptoms of Gaucher disease type 1?

A

onset: childhood-adulthood
visceromegaly, thrombocytopenia and/or anemia (bleeding gums), multiple myeloma, growth restriction, bone/joint pain, NO CNS involvement

46
Q

What are the clinical symptoms of Gaucher disease type 2?

A

onset: 3-6 months
rapidly progressive CNS degeneration around 6 months
death from pulmonary and neurologic disease occurs by 2 years
hepatosplenomegaly

47
Q

What are the clinical symptoms of Gaucher disease type 3?

A

hepatosplenomegaly first
CNS deterioration more slowly progressive
Age of onset variable-many live into young adulthood
skeletal involvement may be debilitating

48
Q

Pathogenic variants in what gene are responsible for Gaucher disease?

A

GBA

49
Q

What treatments are available for Gaucher disease?

A

enzyme replacement therapy, substrate reduction therapy, blood transfusions, pain management, total or partial splenectomy

50
Q

What gene is associated with Fabry disease? etiology?

A

GLA
deficiency of alpha-galactosidase A

51
Q

What ocular finding is pathognomonic for Fabry disease?

A

wheel and spoke pattern (corneal opacity)

52
Q

What gene is associated with Krabbe disease? etiology?

A

GALC
deficiency of beta-galactosidase causing accumulation of galactocerebroside
accumulation results in destruction of myelin

53
Q

What are the clinical symptoms of Krabbe disease?

A

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
Q

What category of diseases does Tay Sachs fall into?

A

GM2 Gangliosidoses
along with Sandhoff disease

55
Q

Biochemically, how are Tay Sachs and gangliosidoses differentiated?

A

Tay Sachs: deficiency of hex A
Sandhoff disease: both enzymes affected

56
Q

What are the primary clinical symptoms associated with infantile-onset GM2 gangliosidoses?

A

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
Q

What is the biomarker for MPS?

A

urinary excretion of GAGs

58
Q

What are the types of GAGs involved in MPS?

A

Dermatan sulfate (DS): visceral and bone involvement
Heparan sulfate (HS): CNS involvement
Keratan sulfate (KS): bone involvement (flattening of vertebral bodies)

59
Q

What are the forms of MPS I?

A

Severe - Hurler syndrome
Intermediate - Hurler-Scheie syndrome
Mild - Scheie syndrome

60
Q

What is the treatment for MPS I?

A

ERT approved in 2003

61
Q

What triad is seen in MPS I?

A

DD, hearing loss, and macroglossia

62
Q

What are the major differences between MPS I and II?

A

MPS II has X-linked recessive inheritance and no corneal clouding

63
Q

Which MPS is Sanfilippo syndrome?

A

MPS III

MedGen Part 2 (15 decks)

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