Repeated USMLE Questions Step 1- 230

A 45-year-old man working as a secretary visits the doctor's clinic complaining of tingling and numbness in his hands. Upon conducting a physical examination, the doctor finds that the patient also has decreased sensation in all his fingers, except for the fifth digit. Keeping these in mind, which of the following muscles is usually weakened in patients suffering from this condition?

A- Adductor pollicis

B- Dorsal interossei

C- Lumbricals

D- Opponens pollicis

Answer






The patient is suffering from carpal tunnel syndrome. This condition occurs in those who work for long hours with repetitive hand motions, such as typing on a computer. In carpal tunnel, the median nerve gets compressed, which leads to a reduced sensation on the first three as well as one-half digits. There is also a loss of strength in the thumb due to reduced strength of the opponens pollicis and the abductor pollicis brevis.

The correct answer is D

Repeated USMLE Questions Step 1- 222

A 23 year-old woman was involved in a motor car accident three days ago. She was hypotensive and diagnosed with internal bleeding. She received several units of blood. Today her urine output is very low for the last six hours.  Her urinalysis showed hematuria, proteinuria, muddy brown epithelial cells and granular casts. Her lab tests also show BUN: 26 mg/dL and serum creatinine: 2.6 mg/dL.

What is the most likely diagnosis of her renal pathology?

A-Acute glomerulonephritis

B-Interstitial nephritis

C-Acute tubular necrosis

D-Traumatic avulsion of the ureter

Answer






Acute tubular necrosis (ATN) is the most likely pathology in this case. It is caused by decrease in blood volume which leads to prerenal azotemia. The most common cause of renal failure associated with prerenal azotemia is acute tubular necrosis. It is characterized by rapid decline of renal function and acute elevation of blood urea and serum creatinine. The BUN/creatinine ratio is usually normal as in this case. The muddy brown epithelial cells and granular casts are also typical in ATN. Acute glomerulonephritis is characterized by the humpy lumpy appearance under light microscope and sub epithelial humps under electron microscope. It is type III hypersensitivity forming immune complexes (antigen-antibody complexes) which deposit below the podocyte foot processes of the basement membrane of the glomeruli. It occurs mainly after streptococcal infection. Interstitial nephritis is inflammation of the kidney tissue that surrounds the tubules. It is caused mainly as a side effect of some drugs or post-infection. It is characterized by eosinophilia and eosinophiluria. Traumatic avulsion of the ureter is mainly occurs as a complication of ureteroscopy. There is no mention to any surgery or trauma of any kind in this patient’s history.

The correct answer is C

Repeated USMLE Questions Step 1- 218

A 59 year old man visits his physician for his yearly routine examination. He mentions that his exercise tolerance had been reduced over the last year. He also notes that he experiences shortness of breath and chest pain when he is ascending his home stairs although he lives on the second floor. He smokes 1-2 packs of cigarettes every day for 35 years. He drinks socially and uses recreational drugs occasionally. On examination, his vital signs are as follows: pulse 86/min, blood pressure 140/90 and his BMI is 30. His cardiac examination is unremarkable. He has family history of hypercholesterolemia and coronary disease. His laboratory tests show abnormal lipid profile (LDL: 230 mg/dL and HDL: 32 mg/dL).

What is the most likely vascular pathology in this patient?

A-Atherosclerosis

B-Deep venous thrombosis

C-Hyperplastic arteriosclerosis

D-Medial calcific sclerosis

Answer







This patient has hypercholesterolemia and most probably coronary artery disease revealed by exertional dyspnea and chest pain. At his age and due to other factors such as smoking and familial hypercholesterolemia, coronary artery disease is mostly precipitated by atherosclerosis. Deep venous thrombosis is suspected if the patient complains of pain, tenderness and swelling of one or both of his legs and/or shortness of breath and pleuritic pain. Hyperplastic arteriosclerosis and medial calcific sclerosis usually occur in smaller arteries and arterioles in patients with diabetes and/or hypertension which is not the case in this patient.

The correct answer is A

Repeated USMLE Questions Step 1 - 155

A 23-year-old woman presents to the clinic with a complaint of pain in her left breast since last night. She is breastfeeding her 1-week-old girl. On examination, her temperature is 99.8 F, her pulse is 88/min. and her blood pressure is 120/80. Local examination of the left breast reveals a localized soft tender 1-inch area. Her past medical, surgical and family histories are unremarkable. What is the most likely diagnosis?

A- A clogged milk duct

B- A breast abscess

C- Milk engorgement

D- Mastitis

E- Inflammatory carcinoma




Answer

This is a presentation of a clogged milk duct in which the mass is localized, tender, and not erythematous or firm. There is no fever or any signs of acute inflammation. There is also no signs or family history of cancer. Abscess occurs later if this mass is infected and no treatment applied. Milk engorgement results in generalized involvement of both breasts. A clogged milk duct is diagnosed mainly by exclusion.

The correct answer is A