Approach to the Immunosuppressed Patient with Pulmonary Infiltrates

Pultnonary complications represent a major cause of morbidity and mortality in immunosuppressed patients (IP). The varied etiologies of pulmonary disease in IPs include pyogenic, mycobacterial and opportunistic infections, drug-induced pulmonary interstitial fibrosis, pulmonary parenchymal involvement by the underlying disease process, and intrapulmonary hemorrhage. With the increasing use of corticosteroid and cytotoxic therapy in a variety of nonmalignant diseases, such as vasculitis, dermatomyositis, connective tissue disorders, pemphigus vulgaris, chronic active hepatitis, and others, recognition of the potential complications associated with their use is imperative. Unusual and fulminant infections may complicate immunosuppressive therapy, Corticosteroid drugs impair host defenses by several mechanisms, including lymphocyte depletion, defective cellular imrriunity, inhibition of macrophage migration and phagocytosis, and polymorphonuclear leukocyte dysfunction.' Prolonged corticosteroid therapy in animals may predispose to severe fungal and protozoan infections.^••' Alkylating agents and azothiaprine similarly p.edispose to infectious complications, primarily by their effects on reducing granuiocyte number.'' The development of pulmonary infiltrates in IP requires urgent and aggressive evaluation, since infections may rapidly overwhelm a host with impaired defenses. Delay in therapy by only a few days may preclude a successful outcome. However, the empiric use of multiple antimicrobial and antimycotic agents to cover all possible infectious etiologies may be hazardous due to the potential toxic effects of these drugs. The serious toxicity of antifungal therapy with amphotericin B makes empiric therapy in undiagnosed infections inadvisable.