What Are Causes and Risk Factors of Lupus?
As with other autoimmune diseases, people with lupus share some type of common genetic link. An identical twin of a person with lupus has a threefold to tenfold greater risk of getting lupus than a nonidentical twin. Moreover, first-degree relatives (mother, father, brother, sister) of people with lupus have an eightfold to ninefold increased risk of having lupus compared with the general public.
Although an identical twin is much more likely to have lupus if her identical sibling has lupus, the likelihood of developing the disease in the unaffected twin is not 100%. Despite the nearly identical genetic makeup of identical twins, the probability of the unaffected twin developing the disease if the other twin has it is around 30%-50% or less. This implies that environmental factors may help determine whether or not the disease develops in a person. Outside of random occurrences of lupus, certain drugs, toxins, and diets have been linked in its development. Sun exposure (ultraviolet light) is a known environmental agent that can worsen rashes of patients with lupus and sometimes trigger a flare of the entire disease.
Reversible drug-induced lupus
In the past, the drugs most frequently responsible for drug-induced lupus are procainamide (Procanbid), hydralazine (Apresoline), minocycline (Minocin), phenytoin (Dilantin), and isoniazid (Laniazid). However, newer medications have been associated with drug-induced lupus, such as the new biological agents (etanercept [Enbrel], infliximab [Remicade], and adalimumab [Humira]) used to treat rheumatoid arthritis. Generally, lupus that is caused by a drug exposure goes away once the drug is stopped.
Association with pregnancy and menstruation
Many women with lupus note that symptoms may be worse after ovulation and better at the beginning of the menstrual period. Estrogen has been implicated in making the condition worse, and this problem is currently being studied. Nevertheless, as a result of recent research, we do know that women with lupus may take birth-control medications without risk of activating their disease. Women who have antiphospholipid antibodies (such as cardiolipin antibodies, lupus anticoagulant, and false-positive tests for syphilis/RPR) should not take estrogens or birth-control pills because of the risk of blood clotting. Pregnant mothers with antiphospholipid antibodies have an increased risk of miscarriage and premature birth. Treatments include aspirin and blood-thinning medications (anticoagulant; heparin or low molecular weight heparin, Lovenox).
Pregnancy does not appear to worsen the long-term outcome of patients with lupus. On the other hand, active lupus tends to increase the risk of miscarriage and preterm birth. Babies of lupus mothers with the SSA antibody (anti-Ro antibody) can develop heart electrical abnormalities and a temporary skin rash (lupus neonatorum, also known as neonatal lupus). Pregnant mothers with lupus are monitored closely by obstetricians.