Usmle Biochem High Yield Vignettes

Front 1

Full term neonate of an uneventful delivery becomes mentally retarded and hyperactive and has a musty odor. What is the diagnosis?

Back 1

PKU (cannot fully metabolize phenylalanine)

Front 2

Stressed executive comes home from work, consumes 7 or 8 martinis in rapid succession before dinner and becomes hypoglycemic. What is the mechanism?

Back 2

NADH Increase prevents gluconeogenesisby shunting pyruvate and oxaloacetate to lactate and malate

Front 3

2 year old girl has an increase in abdominal girth, failure to thrive and skin and hair depigmentation. What is the diagnosis?

Back 3

Kwashiorkor

Front 4

Alcoholic develops a rash, diarrhea and altered mental status. What is the vitamin deficiency?

Back 4

Vitamin B3 (niacin deficiency-pellegra and B1 Thiamin deficiency-->Wernicke-Korsikoff syndrome)

Front 5

51 year old man has black spots in his sclera, and has noted that his urine turns black upon standing. What is the diagnosis?

Back 5

Alkaptonuria--> Homogenistic acid oxidase deficiency--> can't metabolize tyrosine or phenylalanine

Front 6

25 year old man complains of severe chest pain and has xanthomas of his Achilles tendon. What is the disease and where is the defect?

Back 6

1) Familial hypercholesterolemia
2) LDL receptor

Front 7

Woman complains of intense muscle cramps and darkened urine after exercise. What is the diagnosis?

Back 7

McArdle's disease or Glycogen storage disease V--> deficiency in muscle phosphorylase leading to accumulation of glycogen

Front 8

2 parents with albinism have a son who is normal . What genetic mechanism can explain why the son is not affected?

Back 8

Locus heterogeneity

Front 9

40 year old man has chronic pancreatitis with pancreatic insufficiency. What vitamins are likely deficient?

Back 9

A,D, E, and K

Front 10

Child exhibits weakness and enlarged calves. What is the disease and how is it inherited?

Back 10

1) Duchenne's muscular dystrophy
2) X-Linked recessive