Jama 2008;301:2578; Nejm 2004;350:2487

Cause: Pneumocystis carinii, reclassified as a fungus from protozoan status in 1988

Pathophys:Diffuse interstitial pneumonitis

Opportunistic, from other people harboring (epidemics in tumor clinic—Ann IM 1975;82:772)

In patients with depressed immunologic responses, eg, hypogammaglobulinemia, "premies," hematopoietic malignancy, immunosuppression, AIDS (vast majority of patients with pneumocystis have AIDS), elderly (Nejm 1991;324:246)

Sx:Dyspnea, nonproductive cough

Si:Normal chest exam or rales; thrush often concomitantly

Die in weeks without rx (50%), with rx mortality ~3%; those requiring ventilator have a 25% survival to hospital d/c (Jama 1995;273:230)

Osteomyelitis rarely (Nejm 1992;326:999) r/o other opportunistics (Acquired Immune Deficiency Syndrome (AIDS))

Lab:

Bact:Hypertonic saline-induced sputum (Ann IM 1988;109:7), stain with Giemsa (72% sens), toluidine blue (80% sens), or with indirect immunofluorescence (92% sens) (Nejm 1988;318:589)

Path: Fiberoptic bronchoscopic bx, lavage, brushings

Xray:Chest shows diffuse interstitial infiltrate, starts perihilar, 98% bilateral. Gallium scan shows hot lungs even with neg plain films, but 50% false positives including sarcoid patients (Nejm 1988;318:1439)

Rx:

(Med Let 1995;37:87; Nejm 1992;327:1853; Ann IM 1988;109:280)

Preventive (Nejm 1995;332:693; Ann IM 1995;122:755): Isolation of infected from other susceptible patients?; under CD4 of 100, Tm/S better than dapsone, which is better than pentamidine.

• Tm/S DS (Arch IM 1996;156:177; Nejm 1987;316:1627) tiw, qd, or bid; or SS qd
• Atovaquone (Nejm 1998;339:1890) 1500 mg po qd, better tolerated than dapsone as backup for Tm/S-intolerant pts
• Dapsone 50 mg po bid or qd or biw w pyrimethamine, or perhaps 100 mg po biw (Am J Med 1993;95:573); when Tm/S intolerant, also helps prevent toxoplasmosis
• Pentamidine aerosol neb 300 mg q 4 wk (Med Let 1989;31:91) iv q2-4wk, or supine (Ann IM 1990;113:677)
• Pyrimethamine + sulfadiazine (Fansidar) perhaps

Treatment:

• Tm/S 2-15 tab po qd as good as pentamidine (Ann IM 1986;105:37); iv works too (Med Let 1981;23:102) 10-20 mg/kg/d; watch rash and marrow. In AIDS patients with severe disease, give with 40 mg methylprednisolone iv or po q 6 h × 7 d, which markedly improves survival from 20 to 75% (Nejm 1990;323:1445, 1451)
• Pentamidine 4 mg/kg/d × 12-14 d (Nejm 1972;287:495), better, less toxic in AIDS patients; watch creatinine
• Tm/Dapsone equi-effective and only 30% become intolerant of it unlike 60% with Tm/S (Nejm 1990;323:776)
• Atovaquone (Meprone) (Ann IM 1994;121:174; Med Let 1993;35:28; Nejm 1991;325:1534), a hydroxynaphthoquinone, 250 mg po tid, which also treats toxo, may be reasonable backup to Tm/S