Beta-thalassaemic trait and systemic lupus erythematosus

The coexistence of haemoglobinopathies and connective tissue disorders has rarely been investigated and published data relating to this matter are only anecdotal. In 1975 we demonstrated that the incidence of the b-thal trait in patients with RA coming from an area in which haemoglobinopathy is endemic, such as Ferrara and Rovigo (the Po Delta, northern Italy), is higher than would be expected based on its occurrence in the general population (19.8% vs 13.1% of a random population from the same two areas). In SLE, varying degrees of anaemia are quite a common finding but only rarely has the issue of concomitant haemoglobinopathies been addressed. To the best of our knowledge 16 reported cases have described the coexistence of sickle cell disease (SCD) and SLE, but only Kaloterakis et al. described a case of sickle cell/b – thalassaemia in a SLE patient. In a study conducted by Montecucco et al. it was stated that the prevalence of the b-thal trait in patients with connective tissue diseases and seronegative spondyloarthropathies is similar to that expected for the whole population according to their geographic distribution, but the conclusion was not supported by consistent data. Previously we observed a markedly lower incidence of the b-thal trait among a lupus population born in Ferrara and Rovigo areas compared to a control population coming from the same two areas. However, these findings were historical and remained unpublished because of the lack of a rigorous methodological approach to gathering and analysing the data. We have now prospectively studied the prevalence of b-thal minor in 177 consecutive SLE patients from the Ferrara and Rovigo areas (32 males and 145 females, mean age 54 years, range 20-89) diagnosed according to the 1997 revised ACR criteria and followed by our Department from 1998 to the present. Their b-thal status was suspected based on findings of a low mean corpuscolar volume, low haemoglobin value, and increased number of red blood cells; the condition was confirmed in all the cases by haemoglobin electrophoresis. In this patient population we found 17 SLE patients (all female, mean age 53 years, range 20-88) with b-thal minor (9.6% of the cases). This prevalence was 0.7 times lower than the expected rate of 13.1% of the control population and almost half of the prevalence previously observed in RA patients (19.8%) coming from the same areas. These data suggest that b-thal subjects exhibit a particular immunological reactivity of different circulating lymphocyte Tcells subpopulations. If we consider that RA is a prevalently Th1-oriented disease and SLE is a prevalently Th2-oriented disease, it could be argued that b-thal might modify the immunological profile of circulating T cells through a different immune reactivity. Obviously confirmation of this hypothesis will require further studies on Tcell subpopulations and their functioning in b-thal subjects. On the basis of these data we conclude that the prevalence of the b-thal trait is higher in our RA patients and lower in our SLE patients compared with the normal population. The reasons for this different frequency and the way in which the b-thal trait interferes with the clinical characteristics of RAand SLE remains a matter of discussion. Large prospective epidemiologic studies will be necessary to determine if the prevalence of serologic and clinical features of immune complex diseases such as SLE is influenced by the coexistence of a haemoglobinopathy.