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Anaemia of varying degree is a quite common finding in systemic lupus erythematosus (SLE), but only rarely has an association with concomitant haemoglobinopathies and, in particular, β thalassaemia minor, been studied.
In Ferrara and Rovigo areas (the Po’ delta, in the north east of Italy) the prevalence of β thalassaemia is higher than in other parts of Italy (13.1% v 2.1%). We have previously studied the prevalence of this haemoglobinopathy in patients with rheumatoid arthritis (RA)1 and, subsequently, in patients with SLE from this area.2 We found that patients with RA have a higher prevalence and patients with SLE have a lower prevalence of β thalassaemia than a control group (19.8% and 9.8% v 13.1%, respectively).
In this study we describe the clinical characteristics and laboratory findings of our patients with SLE with β thalassaemia and compare them with those of patients with SLE without β thalassaemia.
PATIENTS, METHODS, AND RESULTS
Among 177 consecutive patients with SLE (145 female, 32 male, mean age 54 years, range 20–89) born in the Ferrara and Rovigo areas and attending our institution between January 1998 and June 2003 we found 17 subjects with β thalassaemia (all female, mean age 53 years, range 20–88). Clinical and serological characteristics of these subjects were compared with those of 70 patients with SLE without β thalassaemia matched for sex, age, and disease duration coming from the same area.
Tables 1 and 2 show the demographic and clinical findings for patients with SLE with and without β thalassaemia.
The most remarkable findings were a greater prevalence in β thalassaemia patients of an associated Sjögren’s syndrome (SS) (71% v 16%, p<0.0001) and a greater prevalence of central nervous system involvement (59% v 21%, p<0.005), serositis (47% v 17%, p<0.05), and renal disease (18% v 4%, p NS). The laboratory data showed a greater prevalence of extractable nuclear antigen SSA antibodies in patients with β thalassaemia (71% v 23%, p<0.0001) and persistently reduced (at least three consecutive determinations) C3 and/or C4 complement fractions (59% v 27%, p<0.05).
The association between SLE and haemoglobinopathies has been poorly explored to date.
In this study we found a greater prevalence of an associated SS in patients with SLE and β thalassaemia than in those patients with SLE without β thalassaemia. The same finding has already been reported by Montecucco et al in patients with RA with β thalassaemia.5 Reasons for this association are at present unknown. Further studies of patients with different connective tissue disorders should be performed to exclude the possibility that the association is fortuitous.
In addition to SS, all major systemic complications were more prevalent in β thalassaemia patients with SLE. It is unclear whether the increased presence of SSA antibodies among those with β thalassaemia may have some role6 or whether a more severe disease with persistently reduced C3 and C4 levels is typical of patients with β thalassaemia. Both an increased incidence of atherosclerotic events (secondary to the chronic hypercoagulable state7 or to the homocistinaemia8,9) and a reduced ability to bind immune complexes10 have been described in β thalassaemia subjects and might be responsible for a more aggressive disease in these subjects.
In conclusion, in contrast with other systemic rheumatic diseases (RA, in particular), the prevalence of β thalassaemia in patients with SLE seems to be lower than in the general population. However, when the two conditions coexist, SLE seems to have a more severe course and to be more frequently associated with SS.