We report the concordance rate for RA in a nationwide study of 91 monozygotic (MZ) and 112 dizygotic (DZ) pairs. Twin pairs were recruited from both a national media campaign and a 2-month prospective inquiry of all UK rheumatologists. Disease status was established following a structured clinical and serological appraisal, together with radiological assessment where necessary. Zygosity was confirmed using DNA fingerprinting. In all, 14 (15.4%) of the MZ and four (3.6%) of the DZ pairs were disease concordant (risk ratio: 4.3 95% CI 1.5 to 12.6). There was no difference in the concordance between the media and clinical derived twins. Further the excess MZ concordance persisted after adjusting for age, age at disease onset, sex and rheumatoid factor status. Analysing the data in relation to the timing of disease onset in the first affected twin showed that subsequent disease risk in the initially unaffected co-twins of the MZ affected probands increased with increasing duration of follow-up. We conclude that the overall MZ concordance at 15% is lower than the 30% figure normally quoted from a study some 30 years ago and sets a ceiling at the potential genetic contribution to disease susceptibility.

Objective. To determine whether an allelic form of mannose-binding protein (MBP) incapable of activating complement is associated with susceptibility to systemic lupus erythematosus (SLE).Methods. MBP allele frequencies were determined by amplification refractory mutation systempolymerase chain reaction in 102 white SLE patients and 136 controls.Results. The MBP allele that is unable to activate complement was present in 42 SLE patients ( Conclusion. Our results suggest that this allele of the MBP gene represents a minor risk factor for SLE.Both genetic and environmental factors are important in the development of systemic lupus erythematosus (SLE). This is indicated by a disease concordance of -24% in monozygotic twins (1) as compared with only 3% in dizygotic twins (2). It is likely that the genetic component of SLE susceptibility is oligogenic, and it is known that HLA-encoded genes play an important role. Previous studies have shown that HLA-DQ alleles are important risk factors

Objectives-Polymorphism of the phagocyte IgG receptor Fc RIIa may modulate immune complex mediated inflammation, particularly when immune complexes contain IgG2. Previous studies suggest that this polymorphism may be an important risk factor for lupus nephritis. Fc RIIa is biallelic, the alleles R and H each having a gene frequency of about 50%. Nephritis has been associated with an increased frequency of the R allele. The frequency of common Fc RIIa alleles was examined in white subjects from the United Kingdom and Greek subjects with systemic lupus erythematosus (SLE) and healthy controls. Methods-Fc RIIa genotyping was performed using a single step polymerase chain reaction technique, which diVerentiates the two major alleles, R and H. Two study populations were examined: (a) white subjects from the United Kingdom : 66 controls and 81 with SLE (19 of whom had renal disease) and (b) Greek: 52 controls and 42 with SLE (19 with renal disease). Results-No significant relation was observed between Fc RIIa genotype and susceptibility to SLE or SLE nephritis. Conclusions-The Fc RIIa R allele does not seem to be associated with SLE (with or without renal disease) in our United Kingdom white or Greek populations.