Repeated USMLE Questions Step 1- 219

A 23 year old man with a history of Marfan syndrome presents to the ER complaining of sharp pain on the upper back. He is admitted to intensive care unit (ICU) for the risk of aortic dissection.

Which of the following proteins are responsible for the probable development of abdominal aortic aneurysm (AAA) in this patient?

A-Myosin and actin

B-Fibrin and actin

C-Fibrillin and elastin

D-Myosin and fibrin

Answer





Marfan syndrome is a connective tissue disorder caused by FBNI gene mutation on chromosome 15 which results in defective fibrillin. It affects bones, heart, large vessels and eyes. Patients are tall with long extremities, hypermobile joints and long tapering fingers and toes. Aortic aneurysm develops due to cystic medial necrosis of the aorta.

Myosin and actin are not directly affected in Marfan syndrome. It affects fibrillin which forms a sheath around elastin.

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- 217

A 46 year-old woman with a history of fibromyalgia presents to the clinic with a complaint of anxiety, frequent diarrhea and occasional palpitations. She also noticed an unexplained loss of weight and irregular menstrual periods over the last 3 months.

What is the most likely laboratory investigation that could lead to a diagnosis in this case?

A-CT scan of the head

B-MRI of the brain

C-Colonoscopy

D-Cosyntropin stimulation test

E-Serum Thyroid Stimulation Hormone (TSH) level

Answer






This is most likely a case of Graves’ disease. It is an autoimmune disease characterized by the presence of antibodies bind to thyroid-stimulating hormone receptors. They lead to excess thyroid hormone production which results on this patient’s symptoms such as anxiety, diarrhea, arrhythmias, and unexplained loss of weight, heat intolerance and irregular menstrual periods. If serum TSH level is normal then, other tests can be done to exclude other conditions such as pituitary adenoma or GIT abnormalities.

The correct answer is E

Repeated USMLE Questions Step 1- 216

A 21 year old medical student with a history of asthma presents to the clinic for medication refill. He discussed with his physician the pros and cons of treatment with theophylline. One of the disadvantages of using theophylline is low toxic threshold.

Which of these drugs is used to treat theophylline toxicity?

A-Albuterol

B-Atenolol

C- Digoxin

D-Epinephrine

E-Furosemide

Answer







Theophylline is a non-selective phosphodiesterase enzyme inhibitor used in the treatment of asthma and other pulmonary cases. Beta-blockers are the first line of treatment in cases of theophylline toxicity. Other drugs are not used in treatment of theophylline toxicity.

The correct answer is B

Repeated USMLE Questions Step 1- 215

A 6 year-old girl is brought to her pediatrician by her mother. She said that her daughter is frequently bumping into chairs while walking or playing. On examination, she is found to have bitemporal hemianopia. CT scan shows calcification in the pituitary fossa.

What is the most likely diagnosis of this girl?

A-Choriocarcinoma

B-Craniophyrngioma

C-Gangliocytoma

D-Germinoma

E-Teratoma

Answer





Craniopharyngioma is the most common tumor in children. It is derived from remnants of Rathke's pouch. Due to its large size, it is impinging on the optic chiasm causing bitemporal hemianopia. Other tumors are very rare tumors.

The correct answer is B

Repeated USMLE Questions Step 1- 214

A 43 year-old woman visits her physician for a follow up after abdominal hysterectomy. During surgery, the obturator nerve was served.

What is the most likely lost due to this injury?

A-Abduction of the hip joint

B-Adduction of the hip joint

C-Flexion of the knee joint

D-Extension of the knee joint

E-Dorsiflexion of the ankle joint

Answer






Adduction of the hip joint is induced by the muscles of the medical compartment of the thigh which are innervated by the obturator nerve.

The correct answer is B

Repeated USMLE Questions Step 1- 213

A 4 year old boy is brought to his physician by his mother. She is worried and tells you that her son is weak and not developing properly. He chews his fingers and lips constantly and seems to enjoy it. On examination, there is marked loss of tissues on his fingers and lips. His serum and urine uric acid are elevated.

What is the most likely diagnosis of this condition?

A-Gaucher disease

B-Hurler syndrome

C-Lesch-Nyhan syndrome

D-Galactosemia

E-Tay-sachs disease

Answer






This is a typical presentation of Lesch-Nyhan syndrome which is caused by deficiency hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency. Elevated serum and urine uric acid concentration accompanied by self-mutilating behaviors is diagnostic.

The correct answer is C

Repeated USMLE Questions Step 1- 212

Researchers perform a study on foot ulcers caused by diabetes. They collect patients of foot ulcers and divided them into a group of patients with diabetes and another group of non-diabetic patients. The researchers compute the rate of foot ulcers in diabetic patients versus non-diabetic patients.

This study is considered:

A-Case-control study

B-Cohort study

C-Longitudinal study

D-Cross-sectional study

E-Double-blind study

Answer







This study is case-control study as it is retrospective and compared an odds ratio. It is not prospective because the patients already had foot ulcers.

The correct answer is A

Repeated USMLE Questions Step 1- 211

A 72 year-old man complains of itchy skin lesions in the axilla, groin and medial aspect of the thigh. Examination reveals pruritic lesions and bullae in the areas mentioned above and on forearms and lower legs. There are also painful oral lesions. There is no eye involvement and Nikolsky sign is negative.

What is the most likely diagnosis?

A-Pemphigus vulgaris

B-Bullous pemphigoid

C-Cicatricial pemphigoid

D-Scabies

E-Dermatitis herpetiformis






Answer

This lesion is most likely bullous pemphigoid. Painful oral lesions and negative Nikolsky sign besides the sites of the lesions confirm the diagnosis.

The correct answer is B

Repeated USMLE Questions Step 1- 210

While you were conducting the morning round in internal medicine department, one of the patients told you that the nurses are insensitive and irresponsible. You asked him for the reason. He said: "they are not good as doctors". All doctors I'd seen here are sensitive and responsible.

Which of these is the most likely defense mechanism involved in this case?

A-Projection

B-Reaction formation

C-Regression

D-Repression

E-Splitting

Answer:







This defense mechanism is characterized by dividing 2 groups of people into two opposite characters. Doctors are sensitive and responsible while nurses are insensitive and irresponsible. In other words, splitting them . Other choices have different definitions.

The correct answer is E

Repeated USMLE Questions Step 1- 209

A 12 year old child is brought to his psychiatric for an evaluation of abnormal behavior. His teachers contacted his parents several times because he always cheats and lies at school. He also shoots family dog with his BB gun although he gets in trouble doing that. He has no remorse on hitting other kids and has no concern about others' feelings.

Which of the following is the most likely diagnosis?

A- Schizophrenia

B- Attention-deficit hyperactivity disorder (ADHD)

C- Conduct disorder

D- Bipolar disorder






This boy has a typical presentation of conduct disorder. He enjoyed hurting animals as well as human beings. He lies constantly and has no remorse for any trouble he is causing. Most of the children with this disorder develop into antisocial personality disorder when they get older. Signs and symptoms don’t meet the criteria of other choices.

The correct answer is C

Repeated USMLE Questions Step 1- 208

A 48-year-old woman is taken for autopsy after she is pronounced dead. Her family found her unresponsive and the ER team performed CPR but she didn’t respond. The autopsy reveals the cause of death as internal hemorrhage from an artery close to the posterior wall of the body of the stomach due to erosion of a gastric ulcer.

Which of these arteries is most likely involved in this case?

A- Celiac trunk

B- Left gastric artery

C- Right gastric artery

D- Splenic artery

E- Superior mesenteric artery

Answer: 






Celiac trunk, left gastric and right gastric artery are located close to the anterior wall of the body of the stomach while the superior mesenteric artery is located close to the duodenum. Splenic artery runs close to the posterior wall of the body of the stomach. It arises from the celiac artery and passes around the stomach to supply the spleen.

The correct answer is D

Repeated USMLE Questions Step 1- 207

Gluconeogenesis is a metabolic process in which glucose is generated from non-carbohydrate carbon substrates.

Which one of the following substrates does NOT share its carbon in glucose skeleton but rather contributes as an energy source for gluconeogenesis?

A- Acetyl CoA

B- Alpha-ketoglutarate

C- Fumarate

D- Oxaloacetate

E- Succinyl CoA






Acetyl CoA is an energy source as it generates 12 ATP for each citric acid cycle. Other substrates contribute their carbon in glucose skeleton.

The correct answer is A

Repeated USMLE Questions Step 1- 206

A 3 year- old boy is brought to the emergency room by his mother for vomiting and bloody diarrhea for 4 days. She also noticed low urinary output in the past 2 days. He had no similar attacks in the past and his medical and family histories are unremarkable. On examination, his vital signs are within normal limits, no signs of dehydration, no abdominal tenderness or organomegaly and no rashes or any skin manifestations of hemorrhage or internal disease.

Laboratory tests reveal mild anemia, thrombocytopenia and abundant reticulocytes and schistocytes. Urinalysis reveals red blood cells with no casts. Kidney function tests reveal marked increase in serum urea and creatinine. Coagulation profile is normal. Stool Shiga toxin test is positive for Shiga toxin 2.

What is the most likely diagnosis?

A- Idiopathic thrombocytopenic purpura

B- Thrombocytopenic thrombotic purpura

C- Henoch-Schonlein purpura

D- Hemolytic uremic syndrome

E- Renal stones







The triad of hemolytic anemia, acute kidney failure and thrombocytopenia is characteristic of hemolytic uremic syndrome. Also, positive Shiga toxin is confirmatory for diagnosis of HUS.

The correct answer is D

Repeated USMLE Questions Step 1- 205

A 20-year old female student represents with a 1-week history of nausea, vomiting and anorexia. She returned 2-weeks ago from a trip to Guatemala. On physical examination, her temperature was 100.3 F, clear chest and she has mild jaundice and a palpable tender liver. Her CBC was normal and her liver function tests are as follows: Serum total bilirubin 3.1 mg/dL. Serum aspartate aminotransferase 1100. Serum alanine aminotransferase 1900. Serum alkaline phosphatase 112. What is the most likely lab test to confirm your diagnosis?

A- IgM antibody to hepatitis A virus

B- Antibody to hepatitis B surface antigen

C- Antibody to hepatitis C virus

D- DNA for Epstein-Burr virus

E- Serum anti-mitochondrial antibodies

Answer: 

This patient has typical presentation of hepatitis A virus infection. His recent travel, short incubation period and mode of infection in addition to lab results confirm this diagnosis. The only option that is almost always positive in hepatitis A virus recent infection is IgM antibody to hepatitis A virus.

The correct answer is A

Repeated USMLE Questions Step 1- 204

A 7-year-old boy has a difficult time at school. He sleeps during most of the classes and doesn't interact with his teachers in class. He is fighting with many of his classmates because of stealing their lunches but he has never started a fight. When teachers tried to contact his family, they found out that his family left a fake address and phone number.

What is the most likely cause of this boy's behavior?

A- Attention-deficit-hyperactive disorder (ADHD)

B- Antisocial personality

C- Child abuse

D- Oppositional defiant disorder (ODD)

E- Mental retardation

Answer:






This boy sleeps in class because he does not sleep well at home. He also steals because he doesn't eat or bring food from home. There is no certain abnormality in his behavior. The most likely cause of this boy's behavior is child abuse.

The correct answer is C

Repeated USMLE Questions Step 1- 203

A 74 year-old man presents to the clinic with a complaint of palpitation and lightheadedness. Image studies revealed blockage of the artery to the SA node.

This artery arises from which of these arteries?

A-Left coronary artery

B-Right coronary artery

C-Circumflex artery

D-Anterior interventricular artery

E-Posterior interventricular artery

Answer







The artery to the SA node is a branch of the right coronary artery.

The correct answer is B

Repeated USMLE Questions Step 1- 202

A 20 year-old male athlete complains of pain and weakness of his right arm. He had a successful surgery on his knee last week. He has been walking with the aid of crutches since then. On examination, he is unable to extend his right arm at the elbow or the hand at the wrist. There is also a sensory deficit over the dorsolateral area of the right hand. Neurological examination is otherwise normal.

Which nerve is most likely related to his symptoms?

A-Axillary nerve

B-Median nerve

C-Radial nerve

D-Suprascapular nerve

E-Ulnar nerve

Answer





This is a typical presentation of radial nerve palsy caused by the compression of the crutches on the spiral groove of the humerus. Inability to extend the elbow and wrist drop is due to defective innervation of triceps, brachioradialis and small extensors in the dorsum of the hand. Sensory innervation to the dorsolateral area of the hand is also affected.

The correct answer is C

Repeated USMLE Questions Step 1- 201

A 28 year-old man has a minor injury as a result of motor car accident. He complains of severe pain due to a scratch on his scalp across the front hairline.

Which of these nerves is responsible for this pain?

A-Trigeminal nerve

B-Facial nerve

C-Vagus nerve

D-Oculomotor nerve

E-Orbital nerve

Answer







The anterior scalp at this area is innervated by the ophthalmic branch of trigeminal nerve.

The correct answer is A

Repeated USMLE Questions Step 1- 200

A 42-year-old man undergoes kidney transplantation. The surgical team inspects the kidney prior to remove it.

What is the first anterior structure within the renal sinus?

A-Renal vein

B-Renal arteries

C-Major calyx

D-Minor calyx

E-Renal pelvis

Answer






VAP is the order of structures of the renal sinus from anterior to posterior (Vein, arteries and pelvis).

The correct answer is A