Repeated USMLE Questions Step 1- Review- 80

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Q- A 30-year-old man presents to the office for progressive pain with urination for 1 year. He also complains of episodes of blood in urine in different occasions. He lived in Egypt until he came to the states 6 months ago. Physical examination reveals suprapubic tenderness. Imaging shows bilateral hydroureter and hydronephrosis and calcification in the region of the bladder. A biopsy of the bladder shows chronic inflammation with fibrosis and granulomas.

Which of the following is the most likely diagnosis?

A- Chronic pyelonephritis

B- Interstitial cystitis

C- Schistosomiasis

D- Systemic lupus erythematosus

C- Schistosomiasis- It is endemic in Northern Africa mainly in Egypt. It is associated with chronic cystitis and calcification of the bladder seen in x-ray is pathognomonic.



Q- 1 in 13 African American babies is born with sickle cell trait. Which of the following is the chance that a newly married African American couple to have a child affected by sickle cell disease?

A- 1/13

B- 1/26

C- 1/169

D- 1/676

D- 1/676- Each parent has 1/13 chance to be a carrier. Sickle cell disease is an autosomal recessive so; the chance of offspring to have the disease is 1/4. The chance that the child is affected by the disease is 1/13X1/13X1/4= 1/676



Q- Which of the following is the enzymatic defect in cases of xeroderma pigmentosa?

A- DNA polymerase

B- DNA ligase

C- Excision repair enzymes

D- RNA polymerase III

C- Excision repair enzymes- Xeroderma pigmentosa is a genetic disease characterized by inability to remove pyrimidine dimers caused by exposure to ultraviolet light. Excision repair enzymes are responsible for fixing this and are defective in this condition.



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