Do children with lupus have fewer male siblings?

It is widely acknowledged that genetic factors play a significant role in the pathogenesis of systemic lupus erythematosus (SLE). However, the female preponderance remains unexplained. We hypothesized that the female preponderance in childhood SLE results from selection early in the course of conception against male fetuses bearing genetic material predisposing to SLE. If this hypothesis is accurate, there should be a decreased number of male children in families with a child with SLE. Alternatively, children with SLE would have fewer male siblings. Further, this hypothesis may apply to other diseases with a female predominance such as pauciarticular onset juvenile rheumatoid arthritis (PaJRA), and not apply to diseases without female preponderance such as systemic onset juvenile rheumatoid arthritis (SoJRA). Chart review of patients with childhood onset SLE and PaJRA revealed a greater number of female children in these families compared with families of patients with SoJRA. Large-scale epidemiologic studies with precise counting of miscarriages and abortions could help to confirm these findings. Detailed studies of genetic and maternal intrauterine factors are required to conclusively prove this hypothesis.