(1) That tophi are always preceded by local inflammatory reaction of varying grades of severity, and that the uratic deposits are sequels thereto;
(2) That in their early stages their presence is betokened by soft red swellings associated often with sensations of pricking and tenderness;
(3) That their transmutation into white pearly concretions is a process that takes months to mature;
(4) That tophi and arthritic outbreaks have a common causal origin.
The question that now thrusts itself upon us is,—What, then, is the cause of the inflammatory phenomena which determines the eruption of tophi, and alike of the arthritic outbreaks?
Garrod’s discovery that uric acid was present in the blood in gout not unnaturally led to the assumption that herein lay the origin of its symptomatology, and what else than confirmatory could be the deposition of uratic deposits here and there in the body. The corollary seemed obvious that, given the presence of a certain proportion of uric acid in the blood, then gout must result. But, unfortunately, it was not so; for, lo! and behold, an excess of uric acid in the blood is in no sense pathognomonic of gout.
Thus, the blood in leukæmia contains a high percentage of uric acid, in some cases exceeding that found in gout, and enduring, moreover, for a longer period. Yet no symptoms distinctive of gout appear, nothing that can be referred to uric acid. But it was contended the reason why gout does not ensue is because simultaneously with increased formation there is increased elimination of uric acid. But, unfortunately, despite augmented excretion, the percentage of uric acid in the blood is still maintained at a high level, and still no gout occurs.
Moreover, it is met with also in nephritis, simple and pernicious anæmia, intestinal inflammation, certain fevers, notably in malaria between attacks, and in typhus after the febrile stage, pneumonia, plumbism, etc. Indeed, the ubiquitousness with which uric acid is found in the blood, and this in conditions wholly distinct from gout, would of itself seem sufficient to dissipate any lingering doubts as to its being anything more than a symptom of gout and not its proximate cause.
Obviously, with these revelations the uric acid theory was within measurable distance of being uprooted. Deposed from its high estate as a causal agent, and accredited with only a symptomatic value, the question arose whether indeed this bogey, “uric acid,” was even capable of fulfilling a minor rôle, of originating any symptoms, much less gout, in its entirety. In other words, is uric acid toxic or non-toxic?
The adherents of the uric acid theory did not hesitate to attribute to its toxic action, not only the severe phenomena of acute attacks, but even all the functional disorders of so-called irregular or visceral gout. By the more ardent advocates, such as Haig, we were treated to a word picture of how solid crystals of uric acid erupted out of the blood-stream, and anchoring themselves in nerve sheathes, the renal substance and the mucous membrane, gave birth to chronic neuralgias, nephritis, rhinitis, and so forth. But, alas, there is very serious doubt as to whether uric acid or the urates are capable of acting even as mechanical, much less as true toxic irritants.
Perhaps the most cogent evidence of the slight toxic effects of uric acid or urates is that derived from a study of the uric acid infarcts so frequently noted in infants dying within the first two weeks of birth. According to Gideon Wells, “little or no change occurs in the renal tubule as a result of these depositions, except such as can be attributed to their mechanical effect.” This same observer, discussing this question of the toxicity of uric acid, observes, “It may be safely stated that at the present time there exists no good evidence which makes it probable that uric acid is responsible for any pathological conditions whatever, except uric acid calculi, uric acid infarcts in the kidneys, and certain manifestations of gout.” His further conclusion is that uric acid possesses but a very slight degree of toxicity, and that an actual intoxication of the organism with this substance probably never occurs.
Again, we have the fact that in instances of malnutrition in children excess of uric acid may occasionally be found in the blood. Yet no symptoms comparable to gout occur, even though uric acid calculi form. Also, as has been pointed out, showers of uric acid may be present in their urine, and yet no symptoms arise, save those referable to mechanical irritation of the renal or vesical tissues.
Turning to experimental researches, the evidence is cumulative as to the non-toxicity of uric acid. Rabbits and dogs seem quite irresponsive, either to its ingestion in large quantities in their food, or to repeated intravenous injections of 1 or 2 grammes thereof, save only that the urine showed a large increase in uric acid.
Again, Ransom, of New York, found that no systemic disturbance ensued in two cases of chronic nephritis, following the taking by the mouth of 3 grammes of uric acid per diem for three days in succession. All that resulted was a notable increase in the uric acid output. In one case, he went further, and on the fourth day administered 6 grammes, but nothing happened.
Walker Hall, with commendable devotion, took large doses of uric acid with resultant headache and malaise, which endured for some hours. But as Luff shrewdly observes, “almost any substance, however (common salt for example), will produce toxic effects if taken in very excessive quantities.” Despite his brief indisposition, Walker Hall maintains that uric acid is rather a symptom of, than the precise materies morbi in gout.
Nor, apparently, even in gouty subjects can aggravation of the condition be induced by intravenous injection of uric acid. Bass and Herzberg did so until the blood content of uric acid reached the high level of 10 mg., and yet no joint attack supervened. Neither, for that matter, has it been possible to establish any relationship between degrees of uricæmia and the incidence or severity of gouty paroxysms.
Again, taking a typical instance of acute gout in the big toe, how difficult to conceive that the same owes its origin to uric acid circulating in the blood especially when we realise that the blood content of uric acid in gout exceeds but by a few milligrammes that in normal blood. Moreover, if it does so, then why does it fail to ensue in leukæmia and in other states associated with uricæmia. Also, we like to think that the penchant of acute gout for the toe is that the circulation is inefficient at this peripheral site. But how often is the circulation all too vigorous in gout, and for that matter frequently feeble in leukæmia and in ill-nourished children. But, notwithstanding that in the two latter conditions, uricæmia exists yet, despite favouring circulatory conditions, they develop no gout.
Garrod contended that the violent pain, intense inflammation, and profound constitutional disturbance of acute gout were due to mechanical irritation occasioned by the sudden deposition of biurate crystals in the delicate interior of the implicated joint. Also, that the absence of constitutional disturbance in the inter-paroxysmal periods was because the deposition of urates, being gradual, the tissues acquired tolerance, and yet, forsooth, this same substance is held responsible for the fulminant outbreak that ensues anon.
But it is, as Ringrose Gore shrewdly observed, “against the usual laws of nature that, if an irritant foreign body remains in any organ the symptoms should quickly subside, while the irritant actually increases, for after each attack, and during the intervals between the attacks, the deposits of such biurate enlarge.” In conclusion, is it not infinitely more probable, as Gore states, that the inflammatory reaction precedes the deposition of urates and that these latter, in short, are the consequence and not the cause of the gouty arthritis?
Reverting to tophi, their experimental production, it is claimed, has been achieved by His.[24] Administering alcohol to dogs and simultaneously injecting them locally with sodium mono-urate, he produced deposits which seemed identical with tophi produced spontaneously in gout. But, unfortunately, up to the present, it has been found impossible to induce their formation by flooding the circulation with urates. The utmost, indeed, that His and other workers in this sphere feel able to postulate is that uric acid is a “weak tissue poison.”[25] Scarcely the words in which to describe the poison responsible for gout! for, as we have before stated, the agent that is responsible for tophi must also be capable of inducing the arthritic phenomena and other features of the disorder.
The sum of our reflections is that the toxicity of uric acid has been grossly over-estimated, and that, like its relative urea, it is practically non-irritating and inert; in other words, it cannot any longer be regarded as the essential cause of the acute or chronic forms of gout, whether of articular or ab-articular site. Moreover, far from its presence in excess in the blood being pathognomonic of gout, it must, as Walker Hall contends, be held merely “as symptomatic of conditions which help or prevent its solubility and excretion and does not itself cause lesions which accompany uricacidæmia.”
Naturally the upholders of the uric acid theory were loth to find their fetish uric acid was allotted a meaningless rôle. That it should be deemed inert was to dislodge the very corner-stone of the imposing superstructure they had been at such pains to raise. Uric acid not responsible for the genesis of gout! But, haply, maybe their position was still unassailable; for what of the purin bases, the forerunners of uric acid? Might not the blame lie with these?
Straightway xanthin, hypoxanthin, adenin, etc., were credited with pernicious potencies.[26] Nor did they lack apparent support from the experimental side. Thus, Mandel affirmed that purin bases, apart from infection, might originate pyrexia. Others, again, noted that in dogs and rabbits fed on adenin, degenerative changes in the kidneys ensued, with deposits resembling uric acid and urates in their substance. The fact, too, that guanin-gout was occasionally met with in swine, also lent colour to their views.
Moreover, that ingestion of these congeners of uric acid led in animals to renal lesions, seemed to support the contention of many, that renal disorder might be the primary cause of gout. But, unfortunately, Kolisch and Weintrand’s assertion that the alloxur bases were found in increased quantities in the urine of gouty patients was contradicted by Schmoll, His, Laquer, and others.
Still more cogent, apparently, the announcement in 1910, by Brugsch and Mallory, that they had seen a typical attack of gout ensue in a gouty patient in sequence to a dose of 0·5 gram of hypoxanthin. Nor did this reaction of gouty persons fail of confirmation, as in the same year, Brugsch and Schittenhelm, in gouty patients, noted attacks of arthritis, after the administration of nucleinic acid.
Nevertheless, we must beware of laying too much stress on isolated experiments of this nature, so hypersensitive are some of the victims to any strange or unaccustomed ingesta. Were all the myriad other determinants of gouty attacks eliminated, over-drinking, trauma, mental disturbances, etc.? for be it recollected, all the victims of these experiments with hypoxanthin and nucleinic acid were gouty subjects, i.e., potentially liable to attacks at any moment.
Even admitting the ingestion of, e.g., hypoxanthin was followed by a gouty outbreak, it must be insisted that mere sequence does not establish causation. Clinically, on the whole, there is little or nothing to support the contention that the purin bases have much to do with the pathogeny of gout. “The proof of the pudding is in the eating,” and contrary to the view, at one time so prevalent, that purin foodstuffs were most deleterious, it has been found that, for the average gouty person, a purin-free dietary is not only not essential, but prejudicial. Those, therefore, who may be inclined to see in the above sequence proof of a causal connection, would do well to recall Bacon’s dictum that “there is in the human mind a peculiar tendency to dwell on affirmative and to overlook negative instances.”
In conclusion, we must affirm our belief that neither uric acid nor its precursors is responsible for the fever, local inflammation, and general constitutional disturbance in gout, for uric acid and the urates are themselves practically non-toxic. Albeit, though holding this view, I do not for one moment suggest that uric acid has nothing whatever to do with gout. The fact that tophi, its pathognomonic stigmata, are compounded of biurate of soda, would per se stamp such an attitude as untenable. On the other hand, uric acid must be viewed in its proper perspective as a concomitant or sequel of gout, the essential cause of which must be sought elsewhere.