Thirty-seven adults with tuberculosis are reported, in whom there was evidence (usually tuberculin conversion) that infection was of primary type. The clinical spectrum of primary tuberculosis ranges from a total lack of symptoms in most to massive miliary tuberculosis in a few. Between these extremes, 9 were observed with minor clinical illness accompanied by parenchymal infiltrate, 11 with pleural effusion, and 16 with chronic tuberculosis. Chronic lesions appeared in some at the site of the primary implantation but were more common in the apex, probably because of hematogenous seeding there in the course of the primary infection.
Of particular interest were 16 patients in whom primary tuberculosis progressed within a few months or years into chronic pulmonary tuberculosis; reinfection appeared to play no role. Such progression supports the "unitary concept" of tuberculosis recently advocated (1-3).
Whenever tuberculin-negative persons (even adults) are exposed to an open case of tuberculosis, infection may take place and be treacherous: primary tuberculosis is difficult to recognize because of mildness of illness, tendency to spontaneous "healing," and lack of prior tuberculin data in most cases. Despite absence of initial illness, primary tuberculosis may progress either sooner or later to chronic tuberculosis. Prevention of serious complication of primary infection can be accomplished by two means: vaccination of persons who must be exposed in work (Peace Corps workers, etc.) with Calmette-Cuérin bacillus to prevent infection, or prophylactic chemotherapy with isoniazid (INH) for those in whom infection has already occurred.