you have to know the definition of confidence interval. The CI = the odds (or likelihood) of finding the true average within a set range. Odds ratio is essentially comparing the odds between cases vs. control for both alcohol consumption and no-alcohol consumption. If one of the answer said, ' There is a 5% chance that the true average is not within the range between 1.8 - 6.6' that would be a legitimate answer

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trauma during mountain hiking + fever + calf swelling and tenderness + crepitus >>> this is a case of gas gangrene which is caused by c.perfringens

c.septicum can also cause gas gangrene so why not it ?

the answer is that c.septicum causes spontaneous gas gangrene with rapid onset and hemorrhagic bullae, BUT it is not associated with trauma (unlike c.perfringens)

in the question,it is mentioned that there was mountain hiking making having trauma more likely and hence c.perfringens is the answer

you should also know that c.septicum can cause colon cancer mostly in presence of IBD&immunosuppresion as risk factors

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myopathy&rhabdomyolysis are common side effects of statins particularly when given with fibrates

myoglobin released from damaged muscle cells may cause acute renal failure

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efficacy is defined as maximal effect regardless of dose (which determines potency)

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the graph shows that pressure in left atrium is rising during systole and there is systolic murmur,this indicates mitral valve incompetence

the only choice that can cause mitral valve incompetence is rupture of chordae tendineae

history of rheumatic valvular disease support diagnosis although it most commonly causes stenosis after many years

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sweet odor when changing diaber + increased isoleucine in urine >>> maple syrup urine disease,in which,degradation of branched amino acids (leucine - isoleucine - valine) is blocked due to ↓ branched-chain 𝞪-ketoacid dehydrogenase

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hyperresonance + absent breath sound >>> pneumothorax

in all other choices ,hyperresonance does not occur

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11- a
dorsal white matter of the upper thoracic spinal cord has only dorsal column tract which carries proprioception and 2 points discrimination -discriminative sensation- (differentiate if one finger is touching you or two fingers at the same time)
pain and temperature are carried my lateral spinothalamic tract
and motor activity are carried by corticospinal tract
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12- e
this patient has decreased bile absorption due to jejunoileal bypass as blie is absorbed from ileum,a decrease in bile absorption by turn will lead to decrease fat and fat soluble vitamins absorption (K,E,D,A) ,hence fecal fat is increased and fat soluble deficiency will develop
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13- a
bcl-2 is antiapoptotic , so when overexpressed , it will decrease cell death
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14- d
history of severe cramping pain in right flank that radiates to groin + pain not releived by position >>> stone
prophylaxis of stone formation is by drinking large amount of water in order not to let solutes concentrate and form stones
although calcium stones are the most common type kidney stones ,decreasing calcium in diet is not helpful as most cases of kidney stones occur in people with normal calcium level (normocalcemia & hypercalciuria) , and calcium absorption is regulated by vit d
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15- d
Chancre: charachterized by mononuclear cell infiltrate dominated by plasma cells with scattered histiocytes; also obliterative endarteritis with thickened small vessels due to proliferation of endothelial cells and fibroblasts
Condyloma lata: resembles condyloma acuminatum, and charachterized by prominent epidermal hyperplasia, more edema, chronic inflammatory infiltrate, but less keratinization, minimal if any koilocytosis

Gummas: have caseous necrosis, chronic inflammatory cell infiltrate, obliterative endarteritis
Healed gummas: become noncontractile scars with arching fibrosis

for more information :

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it is a case of CO poisoning

cherry red skin raises suspicion of either CO or cyanide poisoning

important key to know that headache is the most initial symptom on CO poisoning

in this case PCR is not done
Antibodies like IgG can pass through placenta can't tell if baby was infected or just they were passed

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unobtainable blood pressure indicates severe hypotension due to massive hemorrhage after accident,

decreased blood flow and ischemic injury can cause necrosis of tubular cells and their sloughing into tubular lumen obstructing it leading to oligouria

most affected sites are proximal convoluted tubules and thick ascending limb of loop of henle as they need high amount of energy

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This patient has Stanford A aortic dissection with bleeding into the pericardial space. This explains the chest pain and low blood pressure 80/40 mmhg. It acts like a cardiac tamponade mainly around the outflow tract of the left ventricles and causes backup of blood in the LV and LA. This increases LA pressure and reduces the pulmonary venous return to left side of the heart.
So pcwp ( an indirect measure of LA pressure) goes up. This pressures back up to the lungs and causes increased diastolic pulmonary pressure and that also backs up to increase RA pressure.
The body sensing decreased blood supply to the tissues ( due to the tamponade effect and low BP) fires reflexly to increase heart rate and vasoconstricts to maintain BP. This explains the increased systemic vascular resistance.
Finally cardiac index is a ratio of cardiac output to body surface area = CO/ BSA. In this case, BSA does not change but due to hypotension, CO reduces. Therefore, the cardiac index also drops.

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26- a
it is a new concept that you should know,but even if you do not know the answer ,you can answer correctly:
by exclusion,central thermoregulation is mediated by hypothalamus,skin graft and burns has no rule with this.
injured and inflammed skin may cause release of mediators that act as endogenous pyrogens but this would be acutely not continuous for years.
there is no large difference between normal skin and grafted or scar skin in sensitivity to heat or sunlight to the degreee that cause hyperthermia
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27- e
it is very very very high yield to know everything about metformin as it is highly used nowadays
it inhibits hepatic gluconeogenesis ,it also lead to inhibition of mitochondrial isoform of glycerol-3-phosphate dehydrogenase & complex 1 in electron transport chain in liver.
if you decided to know one single most important thing about metformin , it would be a side effect of LACTIC ACIDOSIS !!!!!!!!!!
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28- e
rifampin inhibits DNA dependent RNA polymerase in prokaryotes (this enzyme makes all three types of RNA in prokaryotes unlike eukaryotes that have 3 types of RNA polymerase)
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29- b
bilateral crackles on auscultation >> pulmonary edema >> left side heart failure (most commonly in USMLE)
S3 >> volume overload
pitting ankle edema >> right side heart failure
low blood pressure + peripheral cyanosis with these clues indicates systolic heart failure (diagnosis is supported by pre-eisting hypertension)
in systolic heart failure >> decrease cardiac output (CO)
right sided heart failure >> increased systemic venous pressure (SVP)
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30- b
after circumflex artery angioplasty, blood will increase to regions supplied by it ,which will be left ventricle
NOTE that this patient has a right dominant heart circulation so posterior descending artery arise from right coronary artery, if it was left dominant or codominant,circumflex artery would share in supply of PDA and hence regions supplied by PDA
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31- c
vegetarian for 12 years + macrocytic anemia + neurological manifestations >>> vit B 12 deficiency
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32- f
6-week-old + projectile vomiting - vomitus free of bile >>> pyloric stenosis
you should know that pyloric stenosis is not present at birth but develops later (within 2 weeks)
congenital megacolon presents in first 2 days of life by failure to pass meconium
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33- a
area postrema is found in medulla and is responsible of vomiting
note that it is one of areas that are not protected by blood brain barrier so it is easily stimulated to produce vomiting by different toxins circulating in the blood.
it is also the target of some antiemetic drugs
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34- d
question stem describes manifestations of parkinsonism disease
in parkinsonism: the lesion is in substantia nigra which is found in midbrain as indicated by the arrow
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35- e
tubular absorption is mostly by active transport using ATP , so high amount of oxygen is used (especially proximal convoluted tubules and thick ascending limb of loop of henle)
while glomerular filtration is a passive process
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36- c
ORS, Oral rehydration solution also contains glucose. This provides energy and helps the sodium–glucose cotransporter protein, which absorbs sodium into the cell much better if glucose is also present. The glucose in the oral rehydration solution ensures that the protein will bring as much sodium as possible into the cell. Bringing more sodium into the cell reduces its water potential, causing water to re-enter the cell from the lumen by osmosis.

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recurrent bacterial infections after birth indicates immunodefficiency disease

the only immunedeficiency disease in the choices that is associated with absence lymphoid tissue is Bruton agammaglobulinemia

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progressive dementia + major depressive disorder + movement disorder + autosomal dominant trait >>> Huntington disease

great variability in the symptom severity and age of onset support the diagnosis

this phenomenon is called anticipation,which means that disease severity increases with earlier onset of the disease with each generation

the more the number of triplet , the more the severity and the earlier is the onset.

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generalized tonic clonic seizures after 3 days of hospital admission with no access to alcohol indicates alcohol withdrawal

moreover,other choices do not cause seizres in withdrawal.

delta9-tetrahydrocannabinol (9THC) may cause tremors and ataxia but not tonic clonic seizures

it is very high yield to know manifestations of alcohol withdrawal:

3-36 hr : tremors (the first manifestation) and other minor symptoms similar to other depressants

12-48 hr : hallucinations (usually visual)

treatment for alcohol withdrawal is benzodiazepines

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under normal conditions, prolactin secreted by lactotrophs in anterior pituitary gland is suppressed by dopamine secreted from hypothalamus.

dopamine antagoinists as metoclopramide will lead to removal of this suppression ,and increase prolactin secretion from anterior pituitary (adenohypophysis) leading to galactorrhea.

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treatment and prevention of influenza A and B is oseltamivir ,a sialic acid analog that acts as neuraminidase inhibitor , decrease release of progony virus

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both hepatitis A and E are transmitted via feco-oral route,have no chronic state and usually self limited

but the main difference is that hepatitis E have a high mortality rate among pregnant women so they should be advised not to travel to any region that is know to be endemic with hepatitis E

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actually,the question asks about the normal histology of the lung

type 1 pneumocytes cover about 97% of alveolar surfaces and their function is gas diffusion

type 2 pneumocytes secrete surfactant and serve as precursors to type 1 cells,proliferate during lung damage

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decreasing to 5 mm will automatically include many cases that were left whose induration size was 5-9.9mm, hence prevalance will increase
incidence should also increase as the no. of new cases that will come are said positive if more than 5mm, earlier the limit was 10 mm. so comparatively no. of cases will increase compared to previous data
you should know that:
prevalence = incidence * duration
so when incidence increases,prevalence also increases

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severe combined immunodefficiency SCID is due to deficiency of IL-2R gamma chain (most common .X-linked) or adenosine deaminase deficiency (autosomal dominant,2nd most common cause)

adenosine deaminase deficiency will lead to accumulation of high amount of adenosine in lymphocytes which is toxic ,so they will not work well

patients with SCID present with recurrent bacterial and viral infections and may also opportunistic infections since birth .

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pattern of getting HLA from parents when you will do full square you will see that are 4 options (3 numbers from one parent are going always together to one gamet)

to make it simple .....
inheritance of HLA is like blood groups but no dominant effect like (A /B )
so a parent may have HLA-dr ( lets call it A) and HLA-dr2 (B) . other parent have HLA-dq4 (C) HLA-dq5(D )
so inheritance would be A B * C D

results would be :

AD

BD
each one of the 4 results would be different . so it is 1/4 chance of being the same

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Proteins Breakdown is done by 2 methods... an ATP independent process by Lysosomes...

other one is ATP dependent Ubiquitin proteosome system...

Cachexia mean muscle wasting.

Protein in the muscle is tagged for degradation with small protein called ubiquitin and the final complex is added to proteasome

So increase conjugation of ubiquitin causes breakdown of muscle

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It’s damage to internal urethral sphincter not external
And the internal urethral sphincter is innervated by parasympathetic (pelvic splanchnic)

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tetracycline as well as sulfonamides have a side effect of photosensitivity