Sixth disease: what is it?
The sixth disease is an infectious disease of viral origin, benign, which affects infants aged between six months and two years: it is commonly known as critical exanthema, pseudorosolia or exanthematous fever of three days, and scientifically as exantema subitum or rosolea infantum .
The sixth disease is particularly frequent in certain periods of the year, especially during the intermediate seasons (autumn and spring); it is transmitted mainly through direct contact with saliva or with the mucus of the infected patient (transmission via airborne).
There is talk of a "sixth" disease because it is the sixth infectious pathology widely and in detail described in medicine, and of "exanthemic" infection because it generates a rash characterized by the appearance of patches and red papules on the skin.
Causes
The sixth disease is generated by a viral infection, supported by human Herpes Virus type 6B (HHV-6B). The virus, after a first attack near salivary glands, mucous membranes and regional lymph nodes, reaches the level of the histocytic reticulum, generating the immune reaction. HHV-6B presents a marked tropism for T lymphocytes, for salivary gland cells and for the nervous system [taken from Manual of pediatrics, by M. Castello].
There is another subtype of Herpes virus: HHV-6A, which generally does not cause any symptoms.
It is good to remember that type 6 Herpes viruses are widespread all over the world; it is estimated that almost all of the population is HIV-positive.
Sometimes the virus responsible for the sixth disease can be confused with human Herpes virus type 7, since the symptoms generated are almost the same as those produced by HHV-6B.
Sixth disease: target
We have seen that infants and infants aged between 6 and 24 months represent the category most at risk of contracting the sixth disease. In general, children under the age of six months are not affected by Herpes virus type 6: the explanation probably lies in the presence of virus-specific antibodies of the mother in the serum of infants.
It is rare - but not impossible - that the sixth disease occurs among adults: however, when the Herpes virus type 6 infects the adult, the symptoms are heavier. The probability of the onset of the disease increases when the subject is affected by AIDS, has undergone a recent organ transplant or, more generally, when it is immunosuppressed.
Symptoms
To learn more: Symptoms Sixth Disease
In the vast majority of cases, the sixth disease occurs in a paucisintomatico way, which means that the onset symptoms are scarce, almost null: the scarcity of hints of the disease can be a problem, since it limits the diagnosis and prevents treatment timely of the same, even if - fortunately - the disease presents a benign course in almost all patients.
After a period of 5-10 days of incubation of the virus, the symptoms of the sixth disease begin with a high fever, which sometimes reaches 41 ° C, accompanied by sore throat, cold, conjunctivitis, vomiting, catarrhal phenomena, diarrhea, nausea, mood modulation, irritability and enlargement of the pharynx. It is not uncommon for the patient to be diagnosed with widespread lymphadenopathy when these symptoms occur. The effects triggered by the virus generally regress in 3 or 4 days: this is the pre-exanthemic phase of the sixth disease.
The transmissibility of the sixth disease is greatest during the febrile phase.
At the end of this first period, the real illness (exanthemic phase) begins, which occurs with the appearance of reddish macules and papules spread throughout the body (in particular: neck, trunk, face, hands and feet). Modulation of mood, in general, also continues at this stage of the pathology, accompanied by muscle-joint pain: it is estimated, in fact, that 20% of children with the sixth disease appear particularly irritable.
After one or two days from the formation of the exanthem, the typical prodromas tend to regress, without causing desquamation (unlike, instead, the fourth illness).
Complications
Although the sixth disease has a benign course in most cases, there is no lack of possible complications: in particularly sensitive and predisposed subjects, high fever could generate febrile seizures, accompanied by tension in the muscle mass, loss of consciousness and stiffening of the limbs. Following the sixth disease, some cases of meningoencephalitis and fulminant hepatitis have been described.
Histological examination
In the initial phase, corresponding to the pre-exanthemic period, the subject has a known leukocytosis, which then evolves into leukopenia and lymphocytosis during the final stage. In subjects suffering from the sixth disease, in particular in adults, there is an evident decline in the immune defenses [taken from the Manual of pediatrics, by M. Castello]
Terminology :
- Leukocytosis : increase in the number of lymphocytes in peripheral blood
- Leukopenia : decrease in the concentration of white blood cells, below 4, 000 / microlitre
- Lymphocytosis : increase in leukocytes in the blood above 4, 000 / microlitre
Diagnosis
Fortunately, the diagnosis of the sixth disease is almost simple, particularly in the infant: this is based on the clinical investigation of the patient. The sixth disease must be distinguished from rubella, measles, Enterovirus and Morbillivrus infections by differential analysis: in this case, the doctor evaluates the clinical aspect of the exanthema and the possible involvement of the retro-auricular lymph nodes and cervical.
In some cases, the sixth disease could be mistaken for an iatrogenic reaction: in this regard, a pharmacological history is necessary.
To ascertain the hypothesized sixth disease, isolation of the pathogen in blood or saliva is sometimes necessary; whereas the above disease is a benign infection and virus isolation tests are quite expensive, these diagnostic strategies are rarely performed.
therapies
Being a viral pathologist, the therapies aimed at healing the sixth disease aim to alleviate the symptoms: in fact, we talk about supportive care .
However, any complications affecting the respiratory system (bacterial superinfections) can be treated with antibiotics. Recommended, possibly, antifebrili (eg paracetamol), in the form of suppositories, sometimes associated with syrups with analgesic and anti-inflammatory properties (eg ibuprofen).
Cryotherapy and ice therapy are also effective: in order to reduce fever, ice packs are recommended on the forehead of the sick child.
When the sixth disease becomes complicated with epileptic seizures, the doctor may recommend diazepam or other anticonvulsant drugs.
