(1) Uric acid is not an intermediate but an end-product of metabolism; and
(2) That the human body is devoid of uric acid-destroying enzymes,
then it follows that man, ipso facto, is potentially liable to uric acid retention and deposition, the same objectivated as tophi. In this innate potentiality of and to uratosis resides the “gouty” diathesis.
If the postulates (1) and (2) be established, then, though it sound rank heresy, it follows that gout is not, chemically speaking, an “error of metabolism.” Not, at any rate, in the ordinary acceptation, viz., not a failure in the transmutation of uric acid into urea and intermediate products. If uric acid be an end-product, then no further cleavage into urea, etc., occurs, and in this connection the failure to discover uricolytic enzymes is significant.
We have before proffered the suggestion that not only local, but constitutional, or systemic influences also play a part in the origin of tophi. Provisionally, therefore, we would infer that—
(1) The tissues of gouty subjects display an abnormal affinity for uric acid, i.e., an increased retention capacity for the same;
(2) That certain chemico-physical factors, previously alluded to (content of sodium ions, etc.), favour the incidence of uratic deposits in particular tissues.
In other words, we have in these two elements haply the constitutional and local factors that we postulate as essential to the formation of tophi. Albeit, they represent but latent tissue potentialities, inadequate of themselves to determine the eruption of tophi.
Moreover, be it recalled that the causa causans of gout must be responsible not only for the incidence of tophi, but also for the more dramatic features of gout, its arthritic outbreaks, etc. To dissociate the cause or causes of the uratic deposits from that of the joint inflammations would indeed appear impermissible.
But, taking this view, it is clear that, apart from the constitutional and local factors above postulated, tophi and, alike, the arthritic phenomena of gout, demand for their production the intrusion of some further element, some tertium quid, vital and biological. To this end, therefore, we purpose reviewing tophi in their clinical aspects, as herein possibly we may find some further clue to their exact mode of genesis.