1- A 34 year-old man presents to the ER complaining of fevers, chills, headache and malaise. He was in a trip to India 3 weeks ago and he was getting some flea bites all over his body during his trip. On physical examination, his vital signs are within normal limits and there is a maculopapular rash all over his trunk and upper thighs. What is your diagnosis? what is causative organism?

This is a case of endemic typhus caused by Rickettsia typhi. It is transmitted by the rat and rat flea. It is common in developing countries with inadequate rodent control.

2- In a neurochemical experiment, a researcher measures the neurotransmitter level in the brain after electrical stimulation of raphe nuclei, basal nucleus of Meynert, substantia nigra and locus coeruleus of the pons separately. What is the neurotransmitter expected to rise in each of these structures?

This question asks  for the neurotransmitters found in different areas of the brain. Serotonin is found in raphe nuclei, acetylcholine is found in the basal nucleus of Meynert, dopamine in substantia nigra and norepinephrine is found in locus coeruleus of the pons and midbrain.

3- A 24 year-old woman presents with long standing silver-white scaly patches on the skin of elbows, knees and lumbosacral area. What is your diagnosis? what is the etiology (autoimmune, infectious, vascular etc….)?

This is most likely a case of psoriasis. It is an autoimmune disease characterized by chronic silver-white scaly patches with erythematous border. It affects 1-2% of people in the United States. It usually involves the skin of the elbows, knees, scalp, penis and lumbosacral area.