| Gout. | Syphilis. | Tubercle. | Toxæmia. | |
|---|---|---|---|---|
| Pathognomonic symptoms. | 0 | Gumma of iris. | Tubercles of iris. | 0 |
If pathognomonic symptoms were always present the differentiation of the various causes of iritis would be less difficult. But this is not the case, and consequently, whatever the primary cause, the appearances of the iritis, in spite of the pathogenesis, objectively resemble each other in very many instances.[54]
Medical authorities call certain cases (not varieties) of iritis gouty; they are content to rest the diagnosis on the ground that they occur in gouty people. Yet there is not a single ocular symptom which differentiates the disease from a similar one in non-gouty subjects. Before the dogma can be accepted that because a gouty man has iritis it is therefore a gouty iritis and, like the poet’s primrose, nothing more, it must be shown that irido-cyclitis is proportionately more frequent in people who are gouty than in those who are not. Even then it is suggestive, but not conclusive, for it is conceivable that, although gout is not strictly the cause, yet it may so reduce the resisting power of the iris that it becomes a readier prey to some lurking organism.
It is commonly reported that the existence of a gouty diathesis gives to any inflammatory condition of traumatic origin—synovitis, for instance—a special tendency to chronicity, and I would not deny that it may have the same influence in the case of iritis of traumatic endogenous origin.
If then a gouty man is not immune from other possible causes of iritis, one of these, and not gout, may be responsible for it. Especially is a gouty diagnosis doubtful when there is a focus of suppuration in the tonsils, teeth or elsewhere. Also the prolonged hibernation of the gonococcus, for many years after the attack of gonorrhœa, is apt to be overlooked. The presence of excess of uric acid in the blood, which sometimes occurs in these patients, may mislead us into the belief that we have a true gouty iritis to deal with. But even although it is ascertained that a hyperuricæmia of 4-8 mg. of uric acid is present, it is no proof that the co-existing iritis is necessarily gouty. We might have an even higher content of uric acid in the blood in leukæmia, and yet no iritis be present. It may be admitted that on rare occasions iritis occurs in leukæmia, but no one suggests that the leukæmia or the associated iritis is due to uric acid toxæmia. We should be on infinitely surer ground if not uricæmia, but uratosis, were present. We could then, at any rate, confidently assert that, whatever the origin of the iritis, it had supervened in a subject of gouty habit. I do not think that we, as clinical observers of iritis, should go further than to say: “The man is gouty; his iris is inflamed.” Here in Bath, among hecatombs of gouty people, irido-cyclitis is one of the rarer associated diseases requiring treatment. When it does occur it is usually of obviously septic genesis rather than of gouty origin.
Contrasting gonorrhœa with gout, we find in the former when there is systemic infection, as shown by arthritic complications, there may be also iritis, so often, in fact, that it is legitimate to bracket it as a related symptom. It is a toxæmic condition in which we rely on the frequency of the combination to diagnose the cause.
In writing on iritis in 1908,[55] I referred to the rarity of the association of gout and iritis. In an analysis of 17,197 cases of “rheumatism” and rheumatoid arthritis occurring at the Royal Mineral Water Hospital, Bath, in twenty years, there were twenty patients who suffered from acute or subacute iritis. During the same period there were 2,159 gouty patients not one of whom had iritis. In a special hospital it is possible that the diagnosis of gout might be limited by a stricter nosological differentiation than occurs in private practice. It is, moreover, not uncommon for ophthalmic surgeons to see patients who call themselves gouty, or who say that their doctors have told them that they are, and yet on examination no corroboration is found, no clinical outbreak, or, more pertinent, no tophi. They come to us with an attribution of iritis to gout without the filmiest shadow of evidence.
In considering the correlation of cause and effect it not infrequently happens that we find no obvious connection between the one and the other. In syphilis, for instance, alopecia is a usual secondary symptom, and we rely on the frequency of the sequence to satisfy ourselves that it is no mere coincidence. If it could be shown that alopecia did not occur more frequently in syphilitic people than in non-syphilitic we might justly doubt the connection. The same reasoning may be applied to iritis and gout: the association is so rare that it is negligible. To justify a causal connection between diseases the possibility of a fortuitous concurrence must be excluded, for when the double event occurs only very exceptionally, it is difficult to exclude the long arm of coincidence.
A man has iritis and tophi; ergo we say he has gouty iritis. But why? They co-exist, it is true, but where is the link of attachment of cause and effect? How different is our attitude if we know in another case that our tophaceous iritic patient has gonorrhœa. We then say, gonorrhœal iritis in a gouty subject. Would it not also in the first case be more scientific if we frankly confessed that it was an infective iritis of undifferentiated type occurring in a person of gouty diathesis?
In considering the iritides in relation to gout there are two types which demand our attention. With the possible exception of traumatic iritis, this grouping embraces all the etiological varieties of the affection. In the first are those cases which are due to specific infection, such as syphilis, gonorrhœa and tuberculosis. In the second are those infections of undifferentiated type in which the causal germ has not yet been isolated. Now clearly we must read the latter in the light of their analogues, the specific iritides. In them the modes of onset, the clinical course, are duplicated, presenting similar variations, and they are doubtless the reflexes of the varying grades of intensity of the causal organism.