Practice exam 1 Flashcards
Why does a couple have two kids with osteogenesis imperfecta type 2? (the father has 1 in 10 sperm with mutation in the type 1 procollagen gene)
Germline mutation
So OI type 2 has a autosomal dominant inheritence but the question stem doesn’t mention the dad WITH the disorder so the answer is germline mosaicism because the mutation is in the “germ line” aka sperm but not the rest of the body’s cells.
Germline mosaicism can occur with any inheritence pattern but most commonly occurs with aut dom or x linked
Describe venous return, carotid sinus baroreceptor activity, and cerebral blood flow in a HTN man treated with HCTZ as he goes from supine to standing. (he feels faint, light headed, and dizzy)
venous return goes down
carotid sinus baroreceptor activity goes down (BARORECEPTORS= PARASYMPATHETIC… thus this man needs sympathetic to maintain perfusion so baroreceptor activity goes down)
cerebral blood flow goes down
(basically orthostatic hypotension in the setting of low blood volume… not enough cardiac output to maintain adequate perfusion=light headedness and dizziness… baroreceptor activity increases (PNS) when the carotid sinus is stretched)
Down syndrome kid with pancytopenia, lethargy, bruises, pallor, and fever. What will bone marrow show?
Excess lymphoblasts
ALL (acute lymphoblastic leukemia) is commonly associated with Down Syndrome. Crowding of bone marrow by lymphoid precursor cells leads to bone marrow failure. 85% is B cell (CD 10/19/20+). most common cancer in children. Down syndrome older than 5 yo = ALL…. Down syndrome younger than 5 yo = AML.
Presentation= fever (#1), acute onset, recurrent infections, bleeding, fatigue, LAD, hepatosplenomegaly
Blood smear= lymphoblasts (high nuclei to cytoplasm ratio), TdT+ (pre-T [CD3+] and pre-B [CD 10/19+] cell markers)
Tx= chemo, CNS prophylaxis
Prognosis= responsive to tx, likes to spread to CNS and testes
Older man with productive cough, night sweats, fever for 2 weeks. positive PPD but normal sputum culture after 2 days. What is the causal organism and in what cells is it found?
Mycobacterium tuberculosis lives in macrophages… macrophages get called to fight the infection but because the macrophages are the ones infected they worsen/attack the lungs (and activates them promote granuloma formation)
all mycobacterium are stained with acid fast (Zeihl Neelsen)
facultative intracellular. immune system itself causes the damage (aka no toxin specific to TB) but it does have cord factor that leads to macrophage activation and TNF alpha activ. tuberculin protein is what causes the caseation and granulomas, and the delayed hypersensitivity reaction from the skin test. sulfatides, a type of lipid, prevents the phagosome and lysosome fusion.
Positive PPD= current infection, past infection, or the BCG vaccine. (negative can also indicate immunosuppressed)
Can be latent, later can disseminate to other organs (Potts disease=vertebral osteomyelitis caused by TB)
Tx= positive PPD no active disease then isoniazid alone. If infected, give isoniazid + rifampin + pyrazinamide (2 months), then drop pyraz (4 months)… add ethambutol if drug resistant (blocks polymerization of the mycobacterial cell wall… causes optic neuritis)
small child with abdominal pain, constipation, irritability. Living in a 50 yo renovated home and now has pallor, anemia, increased 5-aminolevulinic acid, and high lead conc. Which enzymes are decreased in this patient?
She has lead poisoning. (microcytic anemia)
This affects CNS (wrist drop or foot drop typically), blood, liver, and kidneys.
It inhibits the enzymes ferrochelatase and ALA dehydratase in the heme synthesis pathway. You get basophilic stippling due to the inhibition of rRNA degredation (so rRNA builds up in RBCs). toxicity= reactive oxygen species.
Risk= homes painted before 1974 (or battery recycling plants)
Labs= increased free erythrocyte protoporphyrin, increased lead. can cause a sideroblastic anemia (iron accumulates on outside of RBC… detect with prussian blue stain… alcoholism most common)
Tx= chelating agensts (succimer> penicillamine> dimercaprol (crosses BBB for encephalopathy))
H pylori strain, which mechanism caused the genetic change? original CCC ACT CAA... subsequent isolate CCC CAC TCA... (with early STOP codon)
Slipped strand mispairing= can result in insertions or deletions of one base or many
Though of as the origin of repetitive DNA sequences (evolution)
answer is not transposon insertion even though it looks like one base was inserted because a transposon is a segment of genes
young female treated for plamodium vivax malaria with primaquine and chloroquine to prevent relapses. Why both?
Because primaquine kills hypnozoites
Malaria= cyclic fever at 2-3 day intervals with shaking chills and soaking sweats. hemolytic anemia, bleeding, asymptomatic between attacks, history of travel. Rash, LAD, photophobia, neck stiffness (consider malaria when thinking of meningitis/migraine)
Chloroquine kills the erythrocytic forms of the plasmodium species (causes retinopathy long term)
Primaquine kills latent hypnozoites for P.vivax/ovale
Malaria lifecycle summary: You get malaria from a bite by an infected mosquito. This bite injects malaria-causing parasites into your blood, where they travel to liver cells. In the liver cells, the parasites breed. The cells later burst, letting loose thousands of new parasites that go on to infect more red blood cells. Mosquitoes get malaria from biting a human who has malaria. The mosquito draws the blood into its stomach where malaria parasites breed and infect other red blood cells. In time, the parasites move into the mosquito’s salivary glands. When this happens, the mosquito is then able to infect a human.
Male newborn with right sided aortic arch, low set ears, small chin, low serum calcium. Where is the site of malformation in the patient?
Third and fourth branchial pouches (pouches 3 and 4… arch 4 only)
This baby has DiGeorge syndrome (mneumonic is CATCH22)
C=cardiac abnormality
A= Abnormal facies (low set ears, small chin)
T= Thymic absence or abnormality (also T cell abnormality)
C= Cleft palate
H= hypocalcemia (failure of parathyroid to develop)
22= chromosome 22q11 deletion
pouches are endoderm (line the foregut). pouch 1= ear area pouch 2= tonsil area pouch 3= parathyroid and thymus pouch 4= parathyroids
arches= associated with cranial nerves
clefts/grooves= ectoderm between arches
newborn born at 28 weeks with severe resp distress due to immature alveoli. an increase in which parameters explains the diminished gas exchange?
Lung elastic recoil
Baby lacks surfactant (made in type 2 pneumocytes). surfactant reduces surface tension (surface tension is 2/3rd of the inward elastic recoil forces)… Thus decreased surfactant= increased tension= increased elastic recoil (aka lungs collapse and have a hard time re-inflating)
sudden blindness in left eye. Left eye shows pale opaque fundus and bright red fovea centralis. left eye also with dense scotoma of entire vision field. right eye normal.
6 months later left eye still blind. If left eye is illuminated, what happens in the right pupil?
No constriction because the retinal ganglion cells in the left eye have been destroyed
So basically this is central retinal artery occulsion or “eye stroke”= sudden, profound, painless vision loss in one eye due to a blood clot.
the fovea [highest visual acuity] is cherry red because it has no overlying nerve fiber layer (due to opacification of the nerve fiber layer as it becomes edematous from ischemia)
scotoma= area of blindness surrounded by relatively normal vision (but here its the entire visual field indicating CRAO instead of branched artery occlusion)
So the retina loses blood flow and dies rather quickly (and this dude waited 3 days) so the retina is gone. the pupillary light reflex that controls the pupil on the opposite side requires the retina to detect light in order to work. Thus shining light on the left retinal-dead blind eye causes no contriction on the right pupil
pedigree question: woman comes in for check up, family hx of hereditary telangiectasia. what explains the reason for her health? (which inheritence pattern)
Incomplete penetrance
Rendu-Osler-Weber disease, or hereditary hemorrhagic telangiectasia (HHT), is an autosomal dominant disorder with incomplete penetrance, characterized by vascular anomalies which may virtually develop in many organs
This pedigree supported an autosomal dominant pattern (appears in both sexes equally, both sexes transmit disease, does not skip generations) but the woman in question appears unaffected (same as husband) and child is affected.
incomplete penetrance when some individuals express the associated trait while others do not even though they carry the disease-causing gene (bc autosomal dominant)
the answer is NOT nonpaternity probably because incomplete penetrance fits plus they show genetic relationship to the offspring with lines and also the kid has the same disorder as a bunch of other people in the family and that seems stupid rare
Epstein barr virus is most commonly associated with which diseases?
Nasopharyngeal carcinoma
EBV= human herpes virus type 4. respiratory/saliva transmission. infects B cells and epithelial cells (and can be latent in B cells)
causes:
- mono (positive monospot.. fever, hepatosplenomegaly, LAD, pharyngitis)
- oral hairy leukoplakia (white hairly looking on sides of tongue in AIDS patients)
- Lymphoma (NHL, Burkitts lymphoma, Diffuse large B cell lymphoma, CNS lymphoma, post transplant lymphoproliferative disorder…B cell prolif s/p immunosuppr)
- nasopharyngeal carcinoma
young boy with mental retardation and choreoathetosis being evaluated for lesch nyhan. What is the approximate michaelis constant (Km) in guanine in this patient?
0.2 to 0.5
YOU HAVE TO PLOT IT!!
Km =1/2 Vmax is the key to understanding this question
the vmax =2, so 1/2 vmax =1
the concentration when the v= 1 is somewhere between .2 and .5
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NFkappaB
