DIFFERENTIAL DIAGNOSIS The recognition of a typical case of scarlet fever is by no means difficult. The acute onset of the initial symptoms, the early marked involvement of the gastro-intestinal tract, the prominence of the pharyn geal symptoms, the macular character of the exanthem, the slight increase in size of the individual macules, their bright red color, and the circunioral triangular area of paleness will easily distinguish this condition from measles. The diagnosis of measles is based on the catarrhal symp toms (sneezing, coughing, conjunctivitis) appearing several days before the eruption, Noplik's spots on the buccal mucous membrane, the loca tion of the eruption within the circumoral triangular area of paleness of scarlet fever, the larger size of the macules and their greater prominence. At first they are small, but rapidly increase in size. They show consider ably more variation in size than do the spots in scarlet fever.
After the subsidence of the acute symptoms there is seen a rather intense spotted pigmentation of the skin, which persists for a longer time than in the case of scarlet fever. The trail of the scarlet fever consists in a rather severe redness of the pharynx, angina and raspberry tongue. To base a diagnosis on the character of the desquamation necessitates considerable caution. Only large scales speak with certainty for scarlet fever.
It is not infrequent, however, that the eruptions of scarlet fever and measles are atypical. I have called attention to the occurrence of a morbillous efflorescence (double eruption) in severe cases of scarlet fever. The diagnosis is still further obscured by the appearance in such cases of coryza and conjunctivitis. Furthermore, I have frequently observed that after the fastigium of measles has been passed, the erup tion. especially on the extremities, assumes the macular character seen in scarlet fever. and which is so characteristic of that disease. Therefore, it behooves the observer to proceed cautiously in arriving at a diagnosis, particularly when at various points examples of both types of eruption stand side by side.
The eruption of rbtheln, or German measles, consists of considerably smaller macules than in the case of measles, so that it more nearly resem bles the eruption of scarlet fever: however, the arrangement of the eruption on the face is similar to that seen in measles. The distance between the macules on the trunk and extremities in rotheln is greater than in the case of scarlet fever. Swelling of the lymph-nodes of the nape of the neck supports the diagnosis of rotheln.
The eruption in erythema infectiosunt on the face is like that of scarlet fever; on the extremities the individual spots are large and are most intense in their coloring on the extensor surfaces.
The greatest difficulty in diagnosis, as in the case of all eruptive diseases, is met with in those mild cases in which the symptoms are illy defined. So far as the eruption itself is concerned, confusion is apt to result when there is redness of the skin accompanying any febrile con dition. The circumoral triangular area of amemia may be present., but on the skin of the extremities the eruption is more diffuse, without any macules; there is no (edema of the skin or pigmentation of the icteric type. It is merely a case of hyperwmia of the skin.
The exanthem seen in crying infants bears a very close resemblance to the eruption of scarlet fever, but is easily differentiated from the latter in that it disappears quickly with the cessation of the crying. The red dening of the skin, known as blushing, also conies in this class.
It is by no means easy to differentiate the eczema and sudamina seen in small children, especially (luring the early years of life. Of course, a valuable point in diagnosis is the fact. that children are rarely affected with scarlet fever during the first year of life. However, all these things merely emphasize the fact that a diagnosis of scarlet fever is never to he based on the appearance of the skin. I have seen sixteen cases of scarlet fever in children under one year of age: the youngest child was four months old. Three children were less than six months old.