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Cross reference - year 5 > Chemical Pathology > Flashcards

Chemical Pathology Flashcards

1
Q

3 main purines

A

adenosine
guanosine
inosime

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2
Q

what enzyme is inactive in humans that leads to build up in urate?

A

uricase

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3
Q

how are purines broken down? which enzyme?

A

purines –> hypo-xanthine –> xanthine –> urate (by xanthine oxidase)

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4
Q

levels of urate in men and women

A

men: 0.12-0.42
women: 0.12-0.36

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5
Q

what changes the solubility of urate?

A

decreases with temp and pH

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6
Q

what is FEVA?

A

fractional excretion of uric acid
= 10%
only 10% of filtered urate in urine

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7
Q

de novo purine synthesis pathway
when done?
rate limiting step?

A
  • inefficient
  • only done when high demand
  • rate limiting step PAT
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8
Q

what is the output of the de novo pathway?

A

IMP
AMP
GMP

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9
Q

what is the salvage pathway?

A

predominant
energy efficient
scoops up partially catabolised purines
brings them to produce IMP/GMP

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10
Q

main enzyme in salvage pathway

A

HPRT (aka HGPRT)

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11
Q

what is the problem in Lesch-Nyhan? leads to?

A

absolute deficiency of HGPRT
X-linked
over drive of the de novo pathway = lots of IMP driven down catabolic pathway to produce urate

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12
Q

symptoms of Lesch-Nyhan

A

normal at birth
developmental delay at 6 months
self mutilation

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13
Q

causes of hyperuricaemia

A

increased production: secondary to myeloproliferative etc

decreased excretion: diuretics, lead poisoning, CKD

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14
Q

name of acute vs chronic gout

A 
acute = podagra
chronic = tophaceous
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15
Q

what does -ve birefringent mean?

A

blue when perpendicular to axis of red compensator

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16
Q

how does colchicine work?

A

inhibit manufacture of tubulin

= reduced motility of neutrophils

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17
Q

MoA of probencid

A

uricosuric

increases FEUA

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18
Q

who should not be given allopurinol?

A

patient on azathioprine

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19
Q

in what patients does pseudogout occur in?

A

patients with osteoarthritis

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20
Q

what is the biggest lipoprotein?

A

chylomicrons

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21
Q

what do CM and VLDLs contain?

A

high in TGs

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22
Q

what are the features of LDLs

A

smaller than VLDLs

main carrier of cholesterol

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23
Q

describe how cholesterol gets absorbed, what transporters?

A
  1. cholesterol solubilised in mixed micelles
  2. transported across intestinal epithelium by NPC1L1
  3. ABC G5 and ABC G8 transporters = transport cholesterol back into lumens of intestine

balance between these determines net absorbed

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24
Q

what happens when cholesterol arrives at the liver?

A

it downregulates HMG-CoA reductase

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25
Q

what does HMG-CoA reductase do?

A

produce cholesterol from acetate and mevalonic acid

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26
Q

what are the 2 fates of cholesterol in the liver?

A
  1. hydroxylation into bile acids: by 7 alpha hydroxylase

2. esterification into cholesterol esters: by ACAT

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27
Q

how do VLDLs form? help of what transporter?

A

cholesterol + TGs + apoB packaged into VLDL

with help of MTP transfer protein

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28
Q

what is the main precursor for LDL?

A

VLDL

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29
Q

what does HDL do? what transporter?

A

pick up excess cholesterol from periphery

ABC A1: packages free cholesterol from periphery into HDLs

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30
Q

what does CETP do?

A

cholesterol ester transfer protein
mediates movement of:
- cholesterol from HDL to VLDL
- TG from VLDL to HDL

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31
Q

what is the transport of TGs?

A
  1. fatty foods to fatty acids
  2. fatty acids synthesised into TGs
  3. CM broken down into free fatty acids by lipoprotein lipase in capillaries
  4. free fatty acids taken up by liver/adipose tissue
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32
Q

what happens to these free fatty acids when in the liver?

A

FFAs –> TGs –> packaged into VLDL

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33
Q

what mutations cause familial hypercholesterolaemia (II)?

A

dominant mutation of:

LDLR, ApoB, PCSK9

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34
Q

what causes familial hyperalphalipoprotieinaemia?

A

increase HDL due to deficiency of CETP

protective

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35
Q

what causes phytosterolaemia?

A

mutations in ABC G5 and ABC G8

these normally prevent absorption of steroids

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36
Q

what does PCSK9 do?

A

promotes degradation of LDL receptor

less LDL removed

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37
Q

cause of primary hypertriglyceridaemia type 1

A

deficiency of lipoprotein lipase (normally degrades CM)

deficiency of ApoCII

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38
Q

cause of primary hypertriglyceridaemia type 4

A

increase synthesis of TGs

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39
Q

cause of primary hypertriglyceridaemia type 5

A

deficiency of ApoAV

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40
Q

how does nephrotic syndrome effect fats?

A

loss of protein in urine
decrease serum albumin
increase LDL synthesis

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41
Q

A-lipoproteinaemia

A

deficiency of MTP

low levels of cholesterol

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42
Q

Tangier disease

A

HDL deficiency

ABC A1 mutation

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43
Q

how do fibrates work?

A

lower TGs

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44
Q

MoA of ezetimide

A

cholesterol absorption blocker

blocks NPC1L1

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45
Q

MoA of colestyramine

A

reduced bile acid absorption

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46
Q

Roux-en-Y

A

distal part of jejunum anastomosed to stomach

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47
Q

Bilopancreatic diversion

A

connection made from stomach to terminal ileum

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48
Q

calculating pH

A

pH = log 1/[H+]

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49
Q

how is bicarbonate calculated in lab?

A

[H+] = k x [CO2] / [HCO3-]

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50
Q

what acid base balance does hypokalaemia cause?

A

metabolic alkalosis

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51
Q

causes of metabolic acidosis

A

increase H production (lactic acidosis/ketoacidosis)
increase H excretion (renal failure, RTA)
loss of bicarbonate (fitula)

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52
Q

enzyme implicated in Gilberts

A

UDP glucuronyl transferase

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53
Q

B1 deficiency causes

A

Beri Beri

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54
Q

B3 deficiency

A

Niacin

Pellagra

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55
Q

what is PKU? How does it present?

A

phenylalanine hydroxylase deficiency
phenylananine –> tyrosine
present: low IQ

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56
Q

sensitivity

A

TP/ total number with disease

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57
Q

specificity

A

TN/ total number without disease

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58
Q

PPV

A

TP/ total number with positive test result

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59
Q

what is included in the Guthrie test?

A 
congenital hypothyroidism
SCD
CF
MCAD
PKU
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60
Q

what is MCAD?

A

fatty acid oxidation disorder

can’t produce acetyl-CoA from fatty acids

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61
Q

tx of MCAD

A

make sure child doesn’t get hypoglycaemia

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62
Q

what is homocysteinuria?

A

failure of remethylation of homocysteine

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63
Q

how does it present?

A

lens dislocation
mental retardation
VTE

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64
Q

what is the CF screening test?

A

immune reactive trypsin

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65
Q

what is urea cycle?

A

takes ammonia, produces urea
7 enzymes in the pathway (disorders in all)
= HIGH AMMONIA

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66
Q

investigation findings in urea cycle disorder

A

increase glutamine
increase ammonia
urine orotic acid

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67
Q

treatment of urea cycle disorder

A

remove ammonia, low protein diet

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68
Q

what are the key features of urea cycle disorders?

A
  • vomiting without diarrhoea
  • respiratory alkalosis
  • hyperammonia
  • neuroencephalopathy
  • avoidance/change in diet
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69
Q

features of organic acidurias

A
  • hyperammonaemia
  • metabolic acidosis
  • high anion gap
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70
Q

what is the defect in organic acidurias?

A

defects in complex metabolism of branched chain amino acids

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71
Q

presentation of organic acidurias

A

unusual odour
lethargy
feeding problems

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72
Q

how do mitochondrial fatty acid and beta oxidation diseases present?

A

hypoketotic hypoglycaemia

73
Q

what are the carbohydrate disorders?

A

disorders of breaking down carbs

  1. galactosaemia
  2. glycogen storage disease 1 (Von Gierke disease)
74
Q

what is the deficiency in Galactosaemia?

A

Gal-1-PUT deficiency

75
Q

presentation of Galactosaemia

A 
D+V
conjugated hyperbilrubinaemia
sepsis
hypoglycaemia
bilateral cataracts
76
Q

what is the issue in glycogen storage disorders?

A

lack a phosphotase
increase glycogen in muscle, liver
= hypoglycaemia

77
Q

features and examples of mitochondrial disorders

A

heterplasy
multi-system, especially high energy organs
e.g. Barth, MELAS, Kearns-Sayre

78
Q

what are the differences in the neonatal kidneys?

A
  • low GFR for SA
  • short PT = decreased resorptive capability
  • decrease resorption of bicarb
  • decrease concentrating ability
  • DT unresponsive to aldosterone = Na loss
79
Q

reasons for neonatal hyperbilirubinaemia

A
  • high levels of bilirubin synthesis
  • decrease rate of transport in liver
  • enhanced enterohepatic circulation
80
Q

causes of prolonged neonatal jaundice

A
  • sepsis/hepatitis
  • hypothyroidism
  • breast milk jaundice
81
Q

causes of conjugated hyperbilirunaemia

A
  • biliary atresia
  • ascending cholangitis in TPN
  • metabolic disease (e.g. galactosaemia)
82
Q

genetic causes of rickets

A
  • pseudo-Vit D def I (defective renal hydroxylation)
  • pseudo-Vit D II (receptor defect)
  • familial hypophosphaetamemia (dec reabsorption)
83
Q

what makes haem?

A

made in all cells by ALA synthase

84
Q

what molecule causes neurovisceral symptoms?

A

5-ALA

neurotoxic

85
Q

what causes the skin lesions in pophyria?

A

due to accumulation of porphyrinogens in skin

= oxidised by UV light in circulation

86
Q

what is the most common porphyria?

A

porphyria cutanea tarda

87
Q

what is the most common porphyria in children?

A

erythopoietic protoporphyria

88
Q

what does ALA synthase deficiency lead to?

A

sideroblastic anaemia

89
Q

what does PBG synthase (aka ALA dehydratase) deficiency leave to?

A

acute porphyria

= increase ALA = neuro symptoms, abdo pain

90
Q

what enzyme deficiency causes AIP?

A

HMB synthase

= increase in PBG and ALA

91
Q

symptoms in AIP

A

neurovisceral attacks, no skin symptoms

92
Q

precipitating factors in AIA

A

ALA synthase inducers (e.g. steroids, alcohol), stress, decrease calorie intake

93
Q

treatment of AIP

A
  • avoid attacks
  • IV carbohydrate (inhibits ALA synthase)
  • IV haem arginate
94
Q

what are the 2 acute porphyrias with skin manifestations?

A
  1. hereditray coproporphyria

2. variegate prophyria

95
Q

deficiency in hereditary coproporphyria

A

coproporphyrinogen oxidase

96
Q

deficiency in variegate porphyria

A

protoporphyrinogen oxidase

97
Q

features of HC and VP

A

AD
neuro attack
skin lesions

98
Q

how to differentiate all of the different acute prophyrias

A

check urine and faces for porphyrins
high = HCP and VP
not high = AIP

99
Q

non acute porphyrias?

A
  • congenital erythopoetic porphyria
  • porphyria cutanea tarda
  • erythropoietic protoporphyria
100
Q

enzyme deficiency in congenital erythropoietic prophyrra

A

uroporphyinogen III synthase

101
Q

deficiency in prophyria cutanea tarda

A

uroporphyrinogen decarboxylase

102
Q

enzyme deficiency in erythopoietic protoporphyria

A

ferrocheletase

103
Q

what are EPP and CEP associated with?

A

myelodysplastic syndrome

104
Q

what does percholate block?

A

blocks uptake of iodine to thyroid cells

105
Q

what should you do if starting thyroid meds?

A

ECG

increase myocardial contractility and may be at risk of ischaemia

106
Q

what does excessive thyroxine?

A

osteopaenia and AF

107
Q

what are the levels in subclinical hypothyroidism?

A

T4 level is normal

TSH is high

108
Q

what is subclinical hypothyroism associated with?

A

hypercholesterolaemia

109
Q

what is the MoA of thionamides?

A

prevent conversion of iodide to iodine by TPO

110
Q

what are the roles of PTH?

A
  1. liberation of Ca from bone and increased resorption in kidneys
  2. stimulates 1 alpha hydroxylase = production of calcitriol
  3. stimulates renal phosphate excretion
111
Q

progress of cholecalciferol

A

cholecalciferol to 25-OH D3 (stored/active form)

25-OH D3 to 1,25(OH)2D3 (kidney)

112
Q

what is ALP a by product of?

A

osteoblast activity

113
Q

what is Z-score?

A

age matched control

114
Q

what does ADH act on?

A

acts on V2 receptors in collecting fuct

115
Q

what is the most reliable clinical sign of hypovolaemia?

A

low urinary Na (<20)

116
Q

how does cirrhosis cause hyponatraemia?

A

release of various vasodilation = dec perfusion

117
Q

osmolality in SIADH

A

dec plasma osmolality

inc urine osmolality

118
Q

SIADH treatment

A

Demecyclyine

Tolvaptan

119
Q

treatment of hypernatraemia

A

use dextrose

replace fluid without excess salt

120
Q

what does angiotensin II stimulate?

A

adrenals to produce aldosterone

121
Q

what does aldosterone do?

A

Na resorption
K excretion
(causes reduced degradation of Na channel)

122
Q

what are the causes of hyperkalaemia?

A
  • dec GFR
  • inc renin activity (T4 RTA, NSAIDs)
  • ARBs
  • aldosterone antagonist
  • K release from cells
  • Addisons
123
Q

what causes a hypokalaemia?

A
  • GI/ renal loss
  • redistribution
  • Rare: RTA 1/2, hypomagnesaemia
124
Q

what do Loop diuretics/ Bartter syndrome?

A

block triple transporter in ascending LOH

= more Na delivery to distal nephron = K+ loss

125
Q

what do Thiazide/Gitelman syndrome do?

A

mutation in Na/Cl channel

= more Na delivery + K loss

126
Q

what causes a high aldosterone:renin ratio?

A

primary hyperaldosteronism

= high aldosterone will suppress renin

127
Q

what is the normal anion gap?

A

14-18

128
Q

what is Shmidt’s syndrome?

A

primary hypothyroidism and addisons

129
Q

what is Phaeo associated with?

A

MEN2
VHL
Neurofibromatosis type 1

130
Q

test to do in Cushing’s

A

inferior petrosal sinus sampling

131
Q

what improves survival in BP and diabetes?

A

aggressive management of BP and lipids improves survival = add thiazide

132
Q

what is Evolocumab?

A

PCSK0 monoclonal Ab

133
Q

what does a loss of function mutation in PCSK9 result in?

A

higher LDL receptor levels
= lower LDL cholesterol levels
so if inhibit PCSK9 = removal of LDL cholesterol from plasma

134
Q

what did the UKPDS do?

A

T2DM
blood glucose control must be good from beginning
= legacy effect

135
Q

what did the Accord show?

A

sudden aggressive control of blood glucose in people with poor control
= decreased complications, increased mortality

136
Q

what is an example of a SGLT2 inhibitor?

A

empagliflozin

137
Q

what is the MoA of SLGT2 inhibitors?

A

wee out glucose

decrease blood glucose and decrease BP

138
Q

what is an example of GLP1 analogues?

A

exanatide/ semiglutide

139
Q

what is the MoA of GLP1 analogues?

A

causes increase insulin from pancreas, incretin effect

140
Q

what is an example of DPP-4 inhibitor?

A

Sitagliptin

141
Q

what do DPP-4 inhibitors do?

A

break down GLP-1

142
Q

symptoms of hypoglycaemia

A

adrenergic (tremors, palpitations, sweating)

neuroglycopaenic (confusion, coma)

143
Q

what is the order of hormone change in hypoglycaemia?

A
  1. suppression of insulin
  2. release of glucagon
  3. release of adrenaline
  4. release of cortisol
144
Q

example of sulphonylurea

A

Glipizide

145
Q

MoA of sulphonylurea

A

increase insulin release by binding ATP-sensitive K+ channels

146
Q

how do you calculate clearance?

A

clearance = (urinary concentration x volume)/ plasma concentration

147
Q

what is the current eGFR recommended calculation?

A

CKD-EPI

148
Q

what type of casts in ATN?

A

epithelial casts

149
Q

CKD stages based on GFR levels

A
  1. kidney damage, normal GFR (>90 ml/min)
  2. 60-89 ml/min
  3. 30-50 ml/min
  4. 15-29 ml/min
  5. ESRF <15 or dialysis
150
Q

what causes adynamic bone disease?

A

excessive suppression of PTH

= lower turnover and decreased osteoid

151
Q

high dose dexamethasone result

A

complete failure to suppress dexamethasone = ectopic

pituitary = can be suppressed by high dose dexa

152
Q

what happens at high levels of cortisol (e.g. ectopic ACTH)?

A

cortisol can bind to aldosterone receptors

153
Q

CPFT

A

insulin to induce hypoglycaemia
TRH
LHRH

154
Q

cause of ALP > x5 ULN

A

Paget’s
osteomalacia
cholestasis
cirrhosis

155
Q

cause of ALP < x5 ULN

A

fractures
osteomyelitis
infiltrative disease
hepatitis

156
Q

statin enzyme

A

CYP3A4

157
Q

Vit A (retinol)
Deficiency
Excess
Test

A

Def: colour blindess
Excess: exfoliation hepatitis
test: serum

158
Q

Vit D (Cholecalciferol)

A

Def: osteomalacia
Excess: hypercalcaemia
Test: serum

159
Q 
Vit E (tocopherol)
deficiency
test
A

Def: anaemia/ neuropathy/ malignancy/ IHD
test: serum

160
Q

B1 (thiamin)
Def
Test

A

Def: Beri Beri neuropathy, Wernicke
Test: RBC transketolase

161
Q

B2 (Riboflavin)
Deficiency
Test

A

Def: glossitis
Test: RBC gluthione reductase

162
Q

B6 (Riboflavin)
Def
Excess
Test

A

Def: dermatitis/ anaemia
Excess: neuropathy
Test: RBC AST activation

163
Q

Niacin deficiency

A

pellagara

164
Q

types of Beri Beri

A 
Wet = CVD
Dry = Neuro
165
Q

what is PYY?

A

satiety hormone

increases after meal

166
Q

what is Leptin?

A

anti-hunger hormone

167
Q

what waist circumference major risk?

A

men: >102
women: >88

168
Q

features of metabolic syndrome

A 
fasting glucose > 6.0
HDL: men <1.0, women <1.3
waist circumference: men >102, women >88
HTN: BP >135/80
microalbumin, insulin resistance
169
Q

AST: ALT >2

A

alcoholic liver disease

170
Q

cause of isolated ALT

A

fatty liver disease

171
Q

what are the liver dye tests? use?

A

Indocyanine green/ Bromsulphalen

measures excretory capacity of liver, measures hepatic blood flow

172
Q

enzymes that increase following MI

A

troponins
CK (MB)
AST (3-14 days)
LDH

173
Q

scan for primary neuroendocrine tumours

A

Gallium 68 dotate scan

174
Q

parathyroid scan

A

sesta MIBI

175
Q

phae scan

A

MIBG

176
Q

gram -ve intracellular diplocci

A

Neisseria

177
Q

Gram +ve cocci

A

strep viridans

178
Q

where does strep viridans affect?

A

on damaged valves

aortic and mitral valves

179
Q

what kind of deafness does Paget disease cause?

A

conductive

Cross reference - year 5 (22 decks)

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