When the rash is dark colored, discrete, and slightly elevated, it may be mistaken for measles ; but the absence of sneezing and lachryniation, and the presence of bright red injection of the throat, with an unusually rapid pulse, should furnish a sufficient distinction.
Roseola may be mistaken for scarlatina, but the rose eruption occurs in larger spots, and indeed more resembles measles than the disease we are considering. Moreover, in roseola there is little or no fever ; no swell ing of the joints ; and the rapidity of the pulse is normal or only moderately increased.
Scarlatina may be closely simulated by ague. Dr. Cheadle has described the cases of two children in whom the skin during the hot stage was covered with a bright red rash. This eruption, combined with a quick pulse and a high temperature, was very suggestive of scarlatina, and might easily have been mistaken for it. The distinguishing points are referred to else where (see Ague).
Sometimes in the mild anomalous cases of the disease desquamation may be long delayed, and the absence of peeling may be held to exclude scarlatina. In these cases we are directed by Sir William Jenner to examine the skin about the roots of the finger-nails for signs of scaling, as it may be discovered in this situation as early as a week or ten days from the cessation of the illness.
Scarlet fever is hardly likely to be confounded with diphtheria, for the invasion and general symptoms of the two diseases are very different. It is important, however, not to overlook the possible intercurrence of diph theria as a complication of the fever. If this unfortunate accident happen early, during the first week, there is usually an offensive discharge from the nostrils ; the voice often becomes hoarse ; and there are symptoms of great depression. If it occur at a later period, when the patient seems approaching convalescence, the fever returns ; the throat becomes again painful ; the glands of the neck enlarge and are tender ; there is a dis charge from the nose ; and in most cases the larynx becomes quickly involved. According to Trousseau, scarlatina avoids the larynx, while diphtheria has a well-known tendency to attack the windpipe. The occur rence of hoarseness, or the appearance of an offensive discharge from the nostrils, in any case of scarlatina, should cause us at once to make fresh examination of the throat ; and probably the appearance in the fauces of the dirty-white tough-looking membrane on the deep red swollen surface will at once prove the accuracy of our anticipations.
Prognosis.—Searlatina, is a disease as to the course of which it is unwise to indulge in confident predictions ; for an attack which begins mildly enough may end in a very different manner. Some of the worst cases are those which begin in such a way. Scrofulous children are bad subjects for scarlet fever, and in them an attack of apparently mild type may be fol lowed by a distressing series of complications. Not long ago I attended a young girl who had been subject for years to scrofulous disease of bone in various parts of the body. She was taken with scarlatina. The symp toms were slight at first, and for a fortnight there was no cause for any thing but satisfaction at the favourable progress of the illness. In the middle of the third week all this was changed. The patient first began to complain of rheumatic pains. She was then attacked in rapid succession by albuminous nephritis, peri- and endo-carditis, and double pleurisy. Ulcerative endocarditis then ensued, which led to cerebral embolism with left hemiplegia, and afterwards to renal embolism, with return of the albu minuria, and casts which had previously disappeared. The girl eventually died suddenly on the eighty-ninth day, apparently from clotting in the pulmonary artery. In cases such as this there may be positively no indica tion that the hitherto benign course of the disease is to change so seriously for the worse. When, however, the fever has assumed a severb form in other children of the same family, we must always be prepared for some such catastrophe ; and until the disease is actually at an end we cannot put aside our apprehensions.
Previous ill health from other causes than scrofula does not apparently modify the prognosis ; nor does early infancy influence unfavorably the course of the disease. The exact character the fever is to assume appears to depend upon the type of the epidemic and the constitutional peculiar ities of the patient.