Pathophysiology

Question 1

Bitot spots in vitamin A deficiency

Answer 1

decreased differentiation of epithelial cells into specialized tissue = squamous metaplasia

Question 2

describe the pathophysiological - wernickes encephalopathy in alcoholic patient given IV glucose infusion

Answer 2

thiamine deficiency - impaired glucose breakdown - ATP depletion worsened by glucose

Question 3

how does carcinoid syndrome cause pellagra

Answer 3

pellagra = vitamin B3 (niacin) deficiency
tryptophan is diverted towards serotonin synthesis - niacin is derived from tryptophan

Question 4

increase in what ration occurs with lactic acidosis, fasting hypoglycaemia and steatosis in alcoholism

Answer 4

increase in NADH/NAD due to ethanol metabolism

Question 5

aspirin induced hyperthermia

Answer 5

aspirin increases mitochondrial permeability - decreases proton (H) gradient and increases oxygen consumption = uncoupling and hyperthermia

Question 6

cataract, retinopathy and peripheral neuropathy in diabetics

Answer 6

lens, retina and schwann cells lack sorbitol dehydrogenase = intracellular sorbitol accumulation = osmotic damage

Question 7

recurrent neissiseria bacteraemia

Answer 7

terminal complement deficiencies (C5-C9) = failure of MAC formation

Question 8

antibodies bind to cell surface antigens = cellular destruction, inflammation and destruction

Answer 8

type II hypersensitivity

Question 9

antigen-antibody complex = activates complement = attracts neutrophils

Answer 9

type III hypersensitivity

Question 10

what type of hypersensitivity reaction is an acute haemolytic transfusion reaction

Answer 10

type II
antibody binds cell surface antigen = cellular destruction, inflammation and destruction

Question 11

DiGeorge results from failure of what pharyngeal pouches to form

Answer 11

3rd and 4th
(3rd = inferior parathyroid + thymus, 4th = superior parathyroid + parafollicular C cells)

Question 12

hyper IgM syndrome

Answer 12

defective CD40L on Th cells = class switching effect

Question 13

leukocyte adhesion deficiency

Answer 13

LFA-1 integrin (CD18) defect - impaired phagocyte migration and chemotaxis

Question 14

chediak-higashi syndrome

Answer 14

LYST mutation - microtubule dysfunction = phagocyte-leukocyte fusion defect

Question 15

candida in immunodeficiency

Answer 15

decreased granulocytes (systemic), decreased T cells (local)

Question 16

what type of hypersensitivity reaction graft vs host disease

Answer 16

type IV HSR, HLA mismatch - donor T cells attack host

Question 17

chlamydia resistance to B lactam abx

Answer 17

lack of classic peptidoglycan due to reduced muramic acid

Question 18

pandemic and epidemic influenza infections

Answer 18

pandemic; RNA segment reassortment = antigenic shift

epidemic; mutations in haemagluttin, nuraminidase = antigenic drift

Question 19

prosthetic device infection by staph epidermidis

Answer 19

biofilm production

Question 20

pseudomembranous colitis secondary to c.diff

Answer 20

toxin A+B damages enterocytes = watery diarrhoea

Question 21

shock and DIC by gram negative bacteria

Answer 21

lipid A of LPS –> macrophage complement and tissue factor activation

Question 22

tissue invasion by cancer

Answer 22

decreased E-cadherin function = decreased intracellular junction = basement membrane and ECM degredation by metaloproteinases = cell attachment to ECM = locomotion = vascular dissemination

Question 23

limitless replicative potential of cancer cells

Answer 23

reactivation of telomerase - maintains and lengthens telomeres - prevention of chromosome shortening and lengthening

Question 24

eisenmenger syndrome

Answer 24

uncorrected left to right shunt - increased pulmonary blood flow - remodelling of vasculature causing pulmonary HTN = RVH = right to left shunt

Question 25

thoracic aortic aneurysm

Answer 25

cystic medial degeneration

Question 26

atherosclerosis

Answer 26

endothelial cell dysfunction - macrophage and LDL accumulation - foam cell formation - fatty streaks - smooth muscle cell migration, extracellular matrix deposition - fibrous plaque - complex atheromas

Question 27

what type of hypersensitivity reaction is rheumatic fever

Answer 27

type II antibodies against M protein cross react with self antigens (molecular mimicry)

Question 28

graves opthalmopathy

Answer 28

lymphocytic infiltration, fibroblast secretion of GAGs - increased osmotic muscle swelling and inflammation

Question 29

duodenal atresia

Answer 29

failure to recanalize

Question 30

jejunal/ileal atresia

Answer 30

disruption of SMA = ischaemic necrosis of feta intestine

Question 31

achalasia

Answer 31

loss of postganglionic inhibitory neurones in myenteric plexus = loss of LES relaxation

Question 32

adenoma-carcinoma sequence in colorectal cancer

Answer 32

loss of APC (decreased intracellular adhesion, increased proliferation) --> KRAS mutation (upregulated intracellular signalling) --> loss of tumour suppressor genes (TP53, DCC)

Question 33

Reyes syndrome pathophysiology

Answer 33

aspirin decreases beta-oxidation by reversible inhibition of mitochondrial enzymes

Question 34

alpha1 antitrypsin deficiency in the liver and lung

Answer 34

liver - misfold proteins aggregate in hepatocellular ER = cirrhosis lung - uninhibited elastase in alevoli = poor compliance and panacinar emphysema

Question 35

mechanism of iron overload in haemochromatosis

Answer 35

decreased hepcidin = increased absorption from the gut

Question 36

chromosomes affected in wilsons and haemochromatosis

Answer 36

wilsons - 13 haemachromatosis - 6

Question 37

anaemia of chronic disease

Answer 37

increase hepcidin = decreased release of iron from macrophages = intestinal absorption of iron

Question 38

sickle cell anaemia

Answer 38

point mutation - substitution of glutamic acid for valine in B chain

Question 39

thrombotic thrombocytopenic purpura

Answer 39

decreased ADAMTS13 (vWF metalloproteinase) = decreased degredation of vWF multimers = increased platelet adhesion and aggregation

Question 40

achondroplasia

Answer 40

constitutive activation of FGFR3 = decreased chrondrocyte proliferation = decreased endochondral ossification

Question 41

osteopetrosis

Answer 41

carbonic anhydrase II mutations = decreased ability of osteoclasts to generate acidic environment = decreased bone resorption leading to dense bones prone to fracture and decreased marrow space = pancytopenia

Question 42

Rheumatoid arthritis hypersensitivity reaction

Answer 42

type III

Question 43

SLE hypersensitivity reaction

Answer 43

type III haematological manifestations are type II HSR

Question 44

sjogrens hypersensitivity reaction

Answer 44

type IV

Question 45

genetic association with atopic dermatitis

Answer 45

FLG gene (filaggrin)

Question 46

lesion in the dominant vs non-dominant parietal cortex

Answer 46

dominant - grestman syndrome (acalcula, agraphia, finger agonisa, right left confusion) non-dominant - hemispatial neglect (agonisa of contralateral side)

Question 47

medial medullary syndrome

Answer 47

anterior spinal artery

Question 48

lateral medullary syndrome

Answer 48

posterior inferior cerebellar artery

Question 49

lateral pontine syndrome

Answer 49

anterior inferior cerebellar artery

Question 50

intracellular eosiniophillic proteinaceous rods in hippocampus

Answer 50

Hirano bodies found in alzheimers

Question 51

HIV dementia

Answer 51

diffuse grey matter and subcortical atrophy

Question 52

mutation associated with familial ALS

Answer 52

SOD1

Question 53

spinal muscular atrophy

Answer 53

congenital degeneration of anterior horns SMN1 mutation --> defective snRNP assembly = LMN apoptosis

Question 54

preeclampsia

Answer 54

abnormal placental spiral arteries --> endothelial dysfunction, vasoconstriction, ischaemia = new onset HTN and proteinuria

Question 55

sarcoidosis related hypercalcaemia

Answer 55

non-caseating granulomas = increased macrophage activity = increased 1alpha hydroxylase activity in macrophage = vitamin D activation = increased Ca

Question 56

CAG trinucleotide repeat

Answer 56

huntingtons disease