Name: 

A 36-year-old man is evaluated in the office because of frothy, watery stools that are found to be positive for Giardia lamblia antigen. This is his third episode of giardiasis in the past 10 months. Previous episodes were treated with metronidazole, following which symptoms resolved and G. lamblia antigen was no longer found in stool specimens. The patient has also had two episodes of bronchitis and three episodes of sinusitis over the past 2 years. He is HIV negative and is a lifelong nonsmoker.

Metronidazole is prescribed.

Which of the following diagnostic studies should be done at this time?

A 25-year-old woman is evaluated in the office for a 3-day history of a malodorous vaginal discharge. She does not have itching or irritation. She has been sexually active with the same partner for 6 months and uses condoms. Her medical history is unremarkable.

On physical examination, external genitalia are normal. Pelvic examination reveals a homogeneous, white, malodorous vaginal discharge that does not adhere to the vaginal walls. There is no vaginal erythema. Bimanual examination shows no cervical motion tenderness. Microscopic appearance of a stained wet prep of the vaginal material is shown (Figure 2).

Which of the following is the most likely diagnosis?

A 25-year-old woman is evaluated in the office because of a white, ‘cottage cheese–like” vaginal discharge. She has no dysuria or hematuria and no history of sexually transmitted diseases. The patient has been sexually active with a single male partner for more than 3 years. Her only medication is an oral contraceptive. She and her partner do not use condoms.

Pelvic examination discloses a moderately thick, white vaginal discharge. The cervix is normal, and no ulcers are seen. The pH of the vaginal secretions is <4.5. A wet prep shows no motile organisms, and cervical specimens are sent for ligase chain reaction testing for both gonorrhea and chlamydial infection. A stained specimen of the vaginal material is shown:



Which of the following is the most likely diagnosis?

A 45-year-old man is evaluated in the office for fever of 1 week's duration. Ten days ago, he was seen for upper respiratory tract congestion, cough, right maxillary pain, purulent nasal drainage, and generalized malaise for the previous 2 weeks. He was diagnosed with acute sinusitis and given a 14-day course of cephalexin. He noted improvement in all symptoms within 3 days. On day 4 of treatment, he felt warm and took his temperature; it was 38.5 °C (101.3° F). Fever has persisted daily for the past 7 days. His original symptoms have completely resolved, and he reports feeling well otherwise. He has no prior medical problems, has never been hospitalized, and takes no medications other than the cephalexin. He reports no allergies.

On physical examination, temperature is 38.3 °C (101.1°F), blood pressure is 130/70 mm Hg, and heart rate is 88/min. The throat is normal without postnasal drip, erythema, or exudate. There is no sinus tenderness to palpation. Tympanic membranes are without evidence of inflammation or effusion. There is no lymphadenopathy. Lungs and cardiac examination are normal. There is no hepatic or splenic enlargement. Skin is normal.

Urinalysis and complete blood count are normal.

Which of the following is the most likely cause of his fever?

A 72-year-old woman who lives in a nursing home is brought to the emergency department because of a 2-day decline in alertness. She is normally ambulatory and communicative but requires assistance completing her activities of daily living. She has a history of Alzheimer's dementia and hypertension, and her medications are donepezil and atenolol.

On physical examination, the temperature is 35.0 °C (95.0 °F), blood pressure is 90/60 mm Hg, heart rate is 110/min, and respiration rate is 18/min. She is easily aroused but not communicative, and her skin is cool and mottled. Oxygen saturation is 90% with the patient breathing oxygen, 2 L/min, by nasal cannula. The mucous membranes are dry and crusted. Cardiac examination reveals tachycardia. The lungs are clear. The abdomen is soft, and there is suprapubic tenderness.

Laboratory studies: hemoglobin, 11.5 g/dL; leukocyte count, 15,000/µL (60% neutrophils, 15% band forms, 25% lymphocytes); serum creatinine, 1.6 mg/dL (baseline creatinine, 0.9 mg/dL). Urinalysis reveals 100 leukocytes/hpf; dipstick is positive for leukocyte esterase and nitrite.

Which of the following diagnoses is most consistent with this patient's presentation?