Sixth Disease

SIXTH DISEASE, syn. roseola infantum, exanthema subitum, s. criticum, s. postfebrile, das kritische Dreitagfieberexanthem der kleinen Kinder. The name "sixth" was given to this disease⁴ by the Italian physician Gismondi (Gismondi, 1925) on the assumption that, alongside the three well-known exanthematic diseases of childhood—scarlet fever, measles, and rubella—there exist as independent diseases the fourth (Filatov-Dukes disease) and the fifth (erythema infectiosum) diseases. Sixth disease is characterized by a 3-5-day fever, a critical drop in temperature, a fine-petechial rash appearing rapidly after such a drop, and a typical blood picture. The American physician Zahorsky first drew attention to this disease in 1910 and gave it the descriptive name roseola infantum. Zahorsky's report did not attract attention. In 1921, Veeder and Hempelmann (America) described the same disease, were the first to point out the typical blood picture, and gave the more successful name exanthema subitum; this name well emphasizes two features in the clinical picture of the disease: the sudden, as if unexpected appearance of the rash and its rapid disappearance. Subsequently, a large number of American works appeared (Levy, Westcott, Greenthal, Fischer, etc.). In Europe, the first observations belong to Bokay (Budapest) in 1923. In 1924, the work of Glanzmann (Glanzmann, Bern) appeared under the title: "Kritisches Dreitagfieberexanthem der kleinen Kinder". Subsequently, there were reports from Japan (Ikeda, etc.), Italy (Gismondi), and Germany (Salmon, etc.). In 1926, Glanzmann's monograph appeared (52 own cases and literature). In the USSR, Molchanov (Moscow) first described this disease (7 cases) in 1927, and then there were a number of other reports. The etiology has been studied very little. It is known that a special predisposition is found in infants. Of Glanzmann's 52 cases, 36 occur in the first year and 12 in the second year. Sixth disease occurs much less frequently after the age of 2, although individual cases have been described at ages 6, 10, and 14 (Zahorsky, Veeder, etc.). The infectious nature is recognized by all, but contagion has not been proven. The disease occurs predominantly in the summer and spring months, usually as isolated cases; some authors (Cushing) observed small epidemics in infant departments. Relapses and repeated illnesses are not observed; immunity appears to be durable. Clinical picture. The incubation period is about 7 days according to Glanzmann, 3-4 days according to Faber, and 10 days according to Cushing. One must treat all these data with caution. The disease begins immediately with a sharp rise in temperature to 38-39°; on the second day the temperature often reaches 40° and above. The fever is of a constant type or slightly remittent. On the 4th, sometimes on the 5th-6th day, the temperature drops sharply and critically. Despite the high temperature, the general condition is disturbed only slightly: the children are somewhat restless, sleep poorly, and appetite is reduced. In rare cases, serious nervous phenomena resembling meningitis and even convulsions were observed (Faber). According to most authors, a frequent symptom is mild catarrhal phenomena: a slight runny nose, conjunctivitis, redness of the throat, sometimes a cough; bronchitis is rare, and lung symptoms are absent. Glanzmann observed purulent inflammation of the middle ear with perforation of the eardrum in two cases. Swelling of the cervical glands is usually absent or only slightly expressed. Sometimes dyspeptic disorders are distinctly prominent in the picture of the disease: diarrhea, vomiting; in such cases the authors (Levy, Glanzmann) speak of a gastrointestinal form of Sixth disease. Rash. Simultaneously with the drop in temperature or a few hours later (6-12), the rash appears. It appears first on the back, quickly spreads to the neck, occiput, chest, abdomen, and limbs; on the face there is little rash, with individual spots on the temples and wings of the nose. The basic element of the rash is small pale-pink spots, which sit separately from each other; if the spots take a bright-red color, the rash becomes extremely similar to measles. Often on the trunk, especially on the back, due to the merging of individual spots, a diffuse redness occurs, and the rash takes a scarlet-fever-like character. The rash lasts about 1-2 days and disappears without leaving either pigmentation or desquamation. Blood picture. The blood picture during the rash period is very characteristic: leukopenia (up to 3,000) with simultaneous lymphocytosis (up to 80-90%). The number of polymorphonuclears is reduced (to 2% instead of 20% in the norm). Plasma cells are encountered rarely and not in such quantity as in rubella. On the 7th-9th day, the blood picture becomes normal again. In the very beginning of the disease, during the febrile period, a slightly expressed neutrophil leukocytosis may be present. There is nothing pathological in the urine or internal organs. Prognosis. Favorable. Due to the mild course, the absence of complications, and the apparently negligible infectivity, the practical significance of Sixth disease is reduced exclusively to the possibility of confusion with one of the childhood exanthems, namely scarlet fever, measles, and rubella. Diagnosis. In differential diagnosis, one should be guided by the entire clinical picture, the peculiar course of the disease, as well as the absence of symptoms most characteristic for scarlet fever, measles, and rubella. In particular, the different distribution of the rash (it begins on the back, not on the face) and the absence of enlargement of posterior cervical glands and plasma cells in the blood speak against rubella. It is more difficult to exclude influenza. During the febrile period, in the presence of rhinitis and pharyngitis, one must first think of influenza. The appearance of the rash and leukopenia does not contradict the diagnosis of influenza, but unlike Sixth disease, the rash in influenza is most often of a scarlet-fever-like character, and the catarrhal phenomena—cough, tracheitis, and bronchitis—are expressed more sharply. Glanzmann, the most authoritative authority on exanthema subitum, admits that there are cases, especially during an influenza epidemic, in which the diagnosis cannot be made with certainty. Treatment. Symptomatic. What is Sixth disease in nosological terms? Most authors (Zahorsky, Bokay, Glanzmann, etc.) consider it an independent infectious disease; some consider it a variety of rubella (Levy) or an atypical form of childhood influenza (Ikeda, Tissier, etc.). Finally, there is an attempt to consider Sixth disease as an anaphylactic syndrome caused by various intoxications. Even now, one can say that this last view, as well as Levy's assumption, is the least justified. The question of the affinity of Sixth disease with influenza and its nosological character should be considered open—further observations and comprehensive studies are necessary. As for the name, there are also disagreements. The name "sixth" was given on the assumption that this disease is an independent nosological unit, just as scarlet fever, measles, rubella, the fourth and fifth diseases are; however, at present the independent character of the fourth and fifth diseases is under serious doubt; therefore, it is more correct to abandon the name "sixth" and retain the name which very successfully characterizes the clinical features of the disease, namely exanthema subitum.