When one encounters an unfamiliar combination of signs and symptoms in a patient he must decide whether this is a coincidental assemblage collected by chance in one person or whether it deserves to be called a syndrome. This is not just a matter of musty academic interest for imaginative speculation. Insight into the processes of disease may come from intense scrutiny of the rare as well as the multiplication of large collections of the commonplace. Uniform groups of signs and symptoms which we encounter with some regularity may arise in two general ways. A genetic or metabolic error may produce a number of different lesions when several different organs or systems are involved. Or a disorder in one system or one organ affects others in turn and disorganizes function or distorts tissues removed in locus and differing in function from those at the site of the primary disorder.