DIAGNOSIS.—The establishment of a correct diagnosis where there is question of variola is one of the most critical and important of the duties of a physician. Upon such decisions have turned, again and again, professional success or disaster. To pronounce that case to be variolous which is not of such a nature is to subject one to the indignation of the few and the ridicule of the many. On the other hand, to be guilty of treating a patient with small-pox, and of remaining ignorant of the nature of the malady, is to subject many ignorant people to the danger of exposure to the disease and to render one's self liable for the redress sought by recourse to the civil authorities and the law. It is difficult to decide which predicament is the graver.
Typical variola vera is readily recognized by its characteristic features. As usual, it is the atypical and modified forms where the difficulty most often arises and where the danger to the physician is proportionately increased.
In the invasion stage of the disease it is often impossible to recognize any symptoms characteristic of variola. High fever with severe lumbar pain, considerable gastric distress, and the appearance of one of the invasion rashes (roseola variolosa) would, however, put the observant practitioner on his guard. I have often noticed in these cases a symptom which, apparently insignificant, has on more than one occasion preceded the eruptive period. It is the occurrence upon the centre of the two cheeks of a vivid damask-red blush, occasionally having a purplish-red hue, and with a very remarkable circumscribed area. This may be recognized in children and adults of both sexes when it occurs in typical aspect, and is undoubtedly a hyperæmia of the character of that producing the rashes in Simon's triangles.
When the variolous exanthem first appears the practitioner should secure as soon as practicable a history of the invasion stage if this has not been subject to his personal observation. He should then make careful inquiry as to the possibility of a neighboring source of contagion, and ascertain by inspection whether the person of the patient exhibits the evidences of successful vaccination. In this connection it is always well to estimate the value of the elements represented by (a) the period ascertained as having elapsed since the last successful vaccination; (b) the typical or atypical character of the existing cicatrices of vaccinia; (c) the unicity or multiplicity of the cicatrices simultaneously resulting from vaccinations performed at one and the same date.
Without question, the first papular lesions of variola resemble those of rubeola or measles to an extent which has often deceived the most expert diagnosticians. The distinguishing points are—(1) In measles, catarrhal symptoms (conjunctival, nasal, laryngeal, bronchial), which are usually absent in the early stages of variola, and later are obviously associated with the irritation set up of the pustules of the maturing period. (2) The difference in the temperature record, that noted in the invasion stage of variola varying from 104° to 105° F., while in rubeola it is rarely registered above 103° F. Moreover, in typical variola the defervescence is marked and characteristic on the appearance of the exanthem, while in rubeola, when the rash appears, the temperature is usually sustained at a maximum, and may even rise. (3) The differences in the rashes of the two disorders. The papules of variola, even in its confluent forms, are, when first observed, remarkably discrete and exhibit not the slightest tendency to grouping, while the maculo-papules of rubeola are (a) developed simultaneously on the face and trunk, while those of variola commonly appear first on the face and afterward on the trunk, the older, and larger therefore, in the site of earliest appearance; (b) are set in clusters or groups having a distinct tendency to crescentic arrangement, a symptom decidedly best appreciated by the eye when the eruption is viewed in totality or in large areas with the eye of the observer somewhat removed from the surface; (c) are often made to disappear or pale beneath the pressure of the finger, while there is greater persistence of color in the variolous papules; (d) are surrounded by little or no halo, each elementary lesion of the eruption being abruptly defined upon the sound skin, while the variolous papule is apt to rest upon a circlet of hyperæmic integument.
Even with careful observation of all the specific differences between the two diseases, they may, for a brief time, so resemble each other as to defy the skill of the expert. In all doubtful cases the physician should invariably admit the doubt and defer an exact diagnosis for twenty-four hours. During the delay the variolous exanthem should betray its individuality by the formation of a minute vesicular apex at the summit of several papules.
In scarlatina the uniform diffusion of the exanthematous blush, the absence of papules and vesico-papules, the continuance of the fever after the rash has appeared, the characteristic scarlet or boiled-lobster color of the skin, and the anginose condition of the throat, are all significant symptoms. In hemorrhagic small-pox the color of the integument is a much more purplish and lurid-reddish hue, rapidly reaching that stage where it refuses to pale under the pressure of the finger, and never leaving in the track of the finger-nail quickly drawn over its surface the peculiar transitory yellowish-white line which can be usually obtained in the skin of the patient with scarlatina.
The pustular stage of variola might be confounded with the pustular syphiloderm. But in the latter there should be a history of a chronic rather than of an acute affection, and, as a result, the simultaneous appearance of lesions in very different stages of their career, some distended with pus, others ruptured and crusted, yet others which have recently formed in the immediate vicinity of the oldest lesions, while the latter have been in full involution or have been replaced by superficial losses of tissue.
The resemblance of pustular variola to certain suppurative and other disorders of the sebaceous glands is well attested by the name given by certain French authors to molluscum epitheliale (M. contagiosum, M. sebaceum)—viz. acne varioliformis. But in the case of acneiform disorders the concurrence of comedones, the chronic course of the disease, the absence of fever and systemic disturbance, and the particularly irregular distribution of the lesions upon the face, with failure to appear elsewhere,—all these facts forbid the confusion of the affection with variola. In medicamentous acne, accompanied by the sudden appearance of numerous pustular lesions symmetrically displayed upon the surface, there will indeed be a source of error. In such cases, of course, a history of the ingestion of a medicament capable of producing a rash will afford valuable aid in the diagnosis. In pustular forms of dermatitis medicamentosa there will usually be found a more abundant development of the pus-containing lesions upon the head and both arms and forearms, with no tendency to extension over very large areas of the trunk and lower extremities—a circumstance which a delay of but a few hours will often substantiate.
The absence of marked defervescence is the most characteristic difference between variola in its eruptive stage and typhus, typhoid, and relapsing fevers. Pneumonia, cerebro-spinal meningitis, acute miliary tuberculosis, and gastric fever are all to be differentiated from variola by the occurrence of symptoms characteristic of the involvement of the several organs which in these diseases respectively are more particularly impaired.