36 Corre (La Mère et l'Enfant dans les races humaines, Paris, 1882) states that measles and scarlatina exist in all climates and among all races; however, they are less frequent in warm than in cold climates. This relative rarity may be only apparent, and has only been established by reason of the difficulty of recognizing exanthems among dark-skinned peoples. In the negro the eruption (of measles) often escapes observation, but the general symptoms, the angina, coryza, and bronchitis, and the special coloration of the bucco-pharyngeal membranes, permit the establishment of the diagnosis. The skin appears more tense, and the face especially is puffed and glossy; in passing the hand over the different regions of the body slight elevations are felt—a difference in the level of the skin exists in the affected and unaffected portions. On examining the surface of the body obliquely at a well-pronounced angle of incidence, these elevations can be perceived by the eye. Desquamation, which is very manifest in the negro, also confirms the diagnosis; this desquamation is formed of epidermic débris; it gives rise to a white dust, which is well defined against the black skin. The skin itself seems to have lost its gloss; it is completely dry, and no longer gives the abundant and odoriferous secretion characteristic of the subjects of that race.
In the way of conjectural diagnosis, the presence of an epidemic of measles in the community should be taken into account. Although measles possesses features so characteristic and pronounced, there are a number of other diseases with which it may be confounded, especially in its earlier stages.
There is no other disease which presents so close a resemblance to measles as does rötheln, and it must be confessed that under certain circumstances the question of diagnosis is a perplexing one. In rötheln the appearance of the eruption is often the first symptom of the affection, whereas in measles there is a prodromic period, having a peculiar remittent type of fever, which continues for three or four days. According to Liveing, the short duration of the febrile attack before the eruption appears is one of the most constant and distinctive features wherein rötheln differs from ordinary measles. In some instances, in rötheln the premonitory fever is not at all appreciable. The catarrhal involvement of the mucous membranes is not nearly so marked as in measles, while the very frequent sore throat bears more resemblance to the angina of scarlet fever. In many instances, although by no means constantly, the eruption of rötheln first appears on the chest, and not on the face, as is the rule in measles. It is quite evident that the eruptive spots of rötheln have presented different physical features in different epidemics; but, as a general thing, it may be said that they are smaller than those in measles, of a paler color, and, according to Thomas, not so angular, less indented, and not so often provided with processes, therefore less apt to assume the crescentic arrangement so often seen in measles.37 The incubation period is longer in rötheln than in measles.
37 According to Curtman (St. Louis Courier Med., June, 1882), the eruption of rötheln consists, when not confluent, of single papules, each separated by a distinct small red areola. Not infrequently the papules are large, and sometimes a few pass into vesicles or pustules. In measles the papules are very small, mostly confluent, from four to six landing on a single areola, which is larger than that of rötheln.
In scarlet fever the incubation stage is shorter than in measles, and the constitutional symptoms are apt to be more pronounced; the temperature is higher, the pulse more rapid, and vomiting more frequent. The stage of invasion in scarlatina is but twenty-four hours; in measles, seventy-two. There is absence of the characteristic catarrh of measles, and the presence of severe sore throat, strawberry tongue, and swelling of the lymphatics at the angle of the jaws. In measles the rash begins on the face; in scarlatina, on the neck and chest. In measles the eruption consists of large papules arranged somewhat crescentically, with intervening normal skin, followed by bran-like desquamation; in scarlatina the rash is made up of large patches formed of minute red spots on a bright red, hyperæmic base, and is followed by desquamation in large lamellæ. In measles the rash is brightest on exposed parts; in scarlatina, most vivid on covered regions. The sequelæ of the two diseases are quite different.
There is no great difference in the duration of the invasion stages of variola and rubeola; but in the former disease we have the marked lumbar and sacral pains and vomiting, while in the latter the catarrhal symptoms and photophobia are pathognomonic. When the eruption of small-pox appears there is subsidence of fever; in measles, an exacerbation. A point of great importance in the diagnosis of variola is found in an examination of the mouth and pharynx, for in these situations on the fourth day we will often find the vesicles fully developed, while on the skin they are still in the stage of papulation. When measles assumes the papular form (morbilli papulosi, rougeole bouttoneuse), it is often confounded with the papular stage of small-pox. I have seen a number of such mistakes made. Attention to the general symptoms of the two diseases, however, and particularly an examination of the mucous membranes, will generally clear up any doubt. At any rate, the question will generally settle itself in the next twenty-four hours, for if it be variola the papules will have undergone their specific development and the rubeolous elevations will have become more decidedly macular.
Typhus sometimes offers a certain resemblance to measles. According to Buchanan,38 the eruption of typhus is occasionally, though not commonly, a good deal like that of measles, and appears about the same time after invasion. Coryza, when present and distinct, points to measles. The eruption of typhus is of a smaller pattern, discrete, and not raised; that of measles, often coalescent, crescentic, and elevated. Subcuticular mottling is present in typhus, and absent in measles. The palatal mucous membrane should always be examined in suspected measles.
38 Art. "Typhus" in Reynolds's System Med., Am. ed., p. 262.
As I have never been able to convince myself of the existence of an independent disease called roseola, I am at a loss to give the points of differential diagnosis; on the other hand, the various forms of symptomatic erythema, occurring either as the result of numerous slight derangements of the system, or in connection with grave constitutional disease, should be carefully considered. In the first group of cases the absence of premonitory symptoms, catarrh, etc., and the presence of the smooth, rose-colored macules, mostly on the trunk, and in the latter the existence of symptoms belonging to the primary disease, should prove of assistance. The erythema papulatum of new-born children I have seen mistaken for measles, but the fact that rubeola is exceedingly rare in sucklings, and the absence of fever and catarrhal disturbances, are sufficient grounds for a differential diagnosis.
The erythematous syphilide (roseola syphilitica), particularly when accompanied by fever, may bear some resemblance to the rash of measles; but the history of the case, the circumscribed, indolent character of the syphilide, in many instances sparing the face, the absence of pathognomonic catarrhal symptoms of measles, and the coexistence of other features of syphilis, are quite distinctive.