USMLE First Aid

Question 1

Duchenne disease typically due to

Answer 1

frameshift (deletions, duplications, or nonsense) mutations

Question 2

which protein is defective in duchenne?

Answer 2

dystrophin

Duchenne=Deleted Dystrophin

Question 3

Becker disorder typically due to

Answer 3

non-frameshift insertions

Question 4

which protein is partially defective in Becker’s?

Answer 4

dystrophin

-only partially defective so less severe than Duchenne’s

Question 5

Down syndrome involves which chromosome?

Answer 5

Chromosome 21 (trisomy 21)
-Drinking age (21)

Question 6

Edwards syndrome involves which chromosome?

Answer 6

Chromosome 18 (trisomy 18)
-Election age (18)

Question 7

Patau syndrome involves which chromosome?

Answer 7

Chromosome 13 (trisomy 13)
-Puberty (13)

Question 8

Cri-du-chat syndrome has what notable sx?

Answer 8

high-pitched crying/mewing

cri du chat= cry of cat

Question 9

Fat soluble vitamins

Answer 9

A, D, E, K

Question 10

water soluble vitamins

Answer 10

B1 (thiamine: TTP)
B2 (riboflavin: FAD, FMN)
B3 (niacin: NAD+)
B5 (pantothenic acidS: CoA)
B6 (pyridoxine: PLP)
B7 (biotin)
B9 (folate)
B12 (cobalamin)
C (ascorbic acid)

Question 11

Vit A
aka
function

Answer 11

• Retinol

- vision and skin

Question 12

Vit B1
aka
function

Answer 12

• Thiamin

- in thiamin pyrophospate (TPP), a cofactor for several dehydrogenase enzyme rxns

Question 13

which two conditions result from thiamin deficiency?

Answer 13

• Wernicke-Korsakoff syndrome

- Beriberi

Question 14

Vit B2
aka
function

Answer 14

• Riboflavin

- FAD and FMN are derived from riboFlavin, cofactors in redox rxns

Question 15

Vit B2 deficiency leads to what sx?

Answer 15

Cheilosis
Corneal vascularization
*2Cs of B2

Question 16

Vit B3
aka
function

Answer 16

• Niacin

- NAD derived from niacin

Question 17

Vit B3 deficiency leads to what dz? what are the sx of this dz?

Answer 17

• Pellagra

- Diarrhea, Dementia, Dermatitis (3 D’s of B3)

Question 18

Vit B5
aka
function

Answer 18

• pantothenic acid (B5 is “pento” thenic)

- coenzyme A (CoA) is derived from pantothenic acid

Question 19

Vit B6
aka
function

Answer 19

• pyridoxine
• pyridoxal phosphate (PLP) is derived from pyridoxine, a cofactor in transamination, decarboxylation, glycogen phosphorylase

Question 20

Vit B7
aka
function

Answer 20

• biotin

- cofactor for carboxylation enzymes (add a 1-carbon group)

Question 21

deficiency of biotin is rare, but excessive consumption of what might cause a deficiency?

Answer 21

egg whites or antibiotics

“AVIDin in egg whites AVIDly binds biotion”

Question 22

Vit B9
aka
function

Answer 22

• folate

- tetrahydrofolic acid (THF) derived from folate, (a coenzyme for 1-carbon transfer/methylation)

Question 23

folate deficiency leads to what dz?

Answer 23

macrocytic megaloblastic anemia

hypersegmented polymorphonuclear cells (PMNs)

Question 24

when is folate deficiency seen?

Answer 24

alcoholism

pregnancy

Question 25

Vit B12 aka function storage

Answer 25

- cobalamin - cofactor for homocystein methyltransferase (transfers CH3 groups) and methylmalonyl-CoA mutase - liver, large reserve pool (several years)

Question 26

B12 def leads to what? caused by?

Answer 26

macrocytic megaloblastic anemia hypersegmented PMNs insufficient meat intake -> veganism malabsorption lack of intrinsic factor -> pernicious anemia

Question 27

Vit C aka function

Answer 27

- ascorbic acid | - antioxidant, facilitates iron absorption by reducing it to Fe2+, collagen synthesis, converting dopamine -> NE

Question 28

Vit C def leads to what dz?

Answer 28

scurvy (vit C cause sCurvy due to Collagen synthese defect)

Question 29

Vit D | types

Answer 29

D2- from plants D3- from milk and exposure to sun 25- OH D3 - storage form 1,25-(OH)2 D3 = calcitriol = active form

Question 30

Vit D | function

Answer 30

incr intestinal absorption of calcium and phosphate | incr bone mineralization

Question 31

Vit D deficiency leads to what dz?

Answer 31

Rickets - children | Osteomalacia - adults

Question 32

Vit K aka function

Answer 32

- phytomenadione, phylloquinone, phytoandione | - K is for Klotting, necessary for the maturation of clotting factors II, VII, IX, X and proteins C and S

Question 33

Vit K is an antagonist to which medication?

Answer 33

Warfarin

Question 34

Vit K deficiency leads to? when might this occur?

Answer 34

-neonatal hemorrhage with incr PT and aPTT (extrinsic and intrinsic respectively) and normal bleeding time -neonates have sterile intestines and are therefore unable to synthesize Vit K (therefore Vit K shot is given at birth) and after prolonged use of broad-spectrum abx (disruption of flora)

Question 35

Kwashiorkor, a protein malnutrition dz, has what clinical picture?

Answer 35

``` Kwashiorkor results from a protein def MEAL: Malnutrition Edema Anemia Liver (fatty) ```

Question 36

Marasmus, a total calorie malnutrition dz, has what clinical picture?

Answer 36

Marasmus results in Muscle wasting