PRIMARY ATYPICAL PNEUMONIA, ETIOLOGY UN- KNOWN: THE AVERAGE CLINICAL PICTURE BASED ON THIRTY-SEVEN ORIGINAL CASES *

T H E increasing prevalence of an atypical form of primary pneumonia has commanded more and more attention during the past four years. Much of the literature on the subject is puzzling or contradictory. There is no "single criterion—clinical or laboratory—which characterizes the syndrome/ ' * Diagnosis is arrived at by a process of eliminating similar diseases of known etiology and attempting to check the patient's signs and symptoms against those of groups of cases previously reported. Unfortunately the literature on the subject is still too fresh for the relative value of each sign and symp-tom to have been worked out. Yet from the present maze of apparent con-tradictions among reported groups of cases, there is emerging a clinical • picture sufficiently clear-cut to permit reasonable diagnosis and tentative classification. The present study is based on 37 cases seen between January, 1941, and October, 1942 (12 other cases were seen but are not included because of insufficient data). This small series will serve to illustrate the clinical picture, as well as some of the variations in the literature