The association of the Hb S mutation with a β thalassaemic defect gives arise to another disease, the microdrepanocytic disease. This disease, discovered and described for the first time in the world in 1944 by Silvestroni and Bianco in a subject of white race, is present in all the areas struck by the thalassaemias and by the sickle anaemia, and in Italy especially in the southern regions.
Clinical features of the microdrepanocytosis (compound heterozygosis due to a HbS gene and a β thalassaemic gene: β thal/βS)
In the microdrepanocytic disease, the haematological picture clearly reveals the presence of the usual haematological thalassaemic characters and of morphological alterations of the erythocytes similar to those of the thalassaemia intermedia, In blood samples incubated at 37°C under conditions of oxygen-deficiency, within few times, the sickle deformation of many erythrocytes appears.
Also, in the microdrepanocytosis, the clinical picture shows sudden painful, violent and recurrent crisis, that have various location: bony, articulate and muscular; or visceral, pulmonary, abdominal.
The microdrepanocytic disease course is tied up not only to an elevated HbF level eventually present but also to the β thalassaemia variety present in the affected subject: if the β defect is mild or silent the course is less severe. As consequence, the microdrepanocytosis can have very varying severities.
In Italy, the region most stricken from the sickle disease is Sicily. In this territory, the β mild thalassaemias and the Hb S with the haplotype Benin have a high frequency (factor that attenuates the sickle phenomenon of the cells with Hb S). These two characteristics led the affected microdrepanocytosis subjects to often have enough attenuated clinical pictures.
Sickling syndromes' therapy
The approach to the therapies for the drepanocytic anaemia and for the microdrepanocytosis is very similar.
Today, regular patient cares allow reaching almost always the adult age. The therapy consists in many support applications: haemotransfusions provided not for fighting the anaemic state, that is not serious, but to reduce the Hb S level in the patient blood. They are necessary therefore in progress of serious painful crises, of sequestrations, of cerebral complicances. They also practise in progress of pregnancy or in preparation to the splenectomy.
In the painful crises the employment of analgesic medicines and in the most serious cases of morphine is also necessary
During the painful crises it is also important an abundant hydro-salty administration to fight dangerous dehydrations.
It is often necessary to submit the patients to splenectomy or for the appearance of hypersplenism or for the great dimensions reached by the splenomegaly.
The hydroxyurea is a drug that can also be administered to patients, being able to stimulate the Hb F production.
The bone marrow transplantation is useful only if precociously practised and that is before repeated acute episodes and above all cerebral complicances have caused irreversible vasculopathies. Currently, also in the case of sickling syndromes, as in the Mediterranean anaemia ones, the transplantation is performed only in case of an affected subject with a healthy and hystocompatibile brother. Various experimental approaches are in progress, in order to use the maternal marrow cells but definitive protocols are not ready yet.
Prevention of the sickle disease
The objective can be reached in both the diseases with the same criterions and interventions that are applied in the thalassaemic diseases. However, the interventions will be realized only in the territories with high incidences of sickle anaemia and thalassaemia: therefore in Italy, in the southern regions and especially in Sicily where the average of the thalassaemia is of 6% and of the sickle anaemia is of 2-3%, at least in the oriental part of the island.
In order to avoid a patient birth, in substance, before the marriage, a thalassaemic or a sickle carrier should choose a normal partner; and after the marriage, the prenatal diagnosis and the interruption of pregnancy, in the case of the foetus disease, should be considered.
