Case 1

History. A 47 year-old woman presented with chief complaint of fever to 103 ºF, non-productive cough and dyspnea which has progressed over one week. She was tested HIV-positive 5 years ago at which time her CD4 lymphocyte count was 583. Zidovudine was started, but she stopped taking it after one month and did not return to her doctor for follow-up. She has anorexia and lost 70 pounds over the last 3 months.

She used heroin and cocaine intravenously for a six month period 6 years ago. She does not smoke or drink, has no past STD's and is not sexually active. She has no known drug allergies (NKDA).

Physical Examination. She was pale, diaphoretic and in acute respiratory distress. T 37.4º C, P 96/'min, R 30/min, BP 110/70. Oral thrush was present. Examination of the lungs disclosed poor inspiratory effort and bibasilar crackles 2/3 of the way up the posterior lung field. She had a tachycardia but no murmurs. Her abdomen was nontender, and there was no enlargement of the liver or spleen. Pelvic exam was normal except for vaginal candidiasis. Neurologic examination was normal.

Laboratory Evaluations:

Hgb: 10.8 g/dl
WBC: 7,500/mm3
Segs: 43, Lymphs: 41, Monos: 9, Eos: 6, Basos: 1
Platelets 248k/mm3
ABG: 7.48(pH)/32(pCO2)/51(pO2)/23(HCO3)
CD4: %=11.#=235/mm3
HIV RNA level: 234,000 copies/ml
Induced sputum: Direct fluorescence positive for Pneumocystis carinii

Questions

2. How is Pneumocystis carinii acquired? Was this patient recently infected?

3. What is the mechanism by which Pneumocystis carinii causes pneumonia?

4. How is infection with Pneumocystis carinii diagnosed?

The patient is started on intravenous trimethoprim/sulfamethoxazole (20 mg/kg/D trimethoprim: 100 mg/kg/D sulfamethoxazole) plus prednisone 40 mg twice daily. Two days later she is improved: respiratory rate is down to 18/min, O2 saturation is 98% with FiO2 of 21%. Trimethoprim sulfamethoxazole therapy is changed to oral. On day 5, she develops fever, a morbilliform rash and elevations of AST, ALT and alkaline phosphatase.

6. What alternative therapies are available? 

7. What is the likelihood of an adverse reaction to trimethoprim sulfamethoxazole in a patient with AIDS?  

8. Can relapses of pneumonia due to Pneumocystis carinii be prevented? How?