Researchers have found what can cause Lupus in children. From the article:

Sometimes a single mutation in our genetic make-up is enough to cause disease. This is also the case with the autoimmune disease lupus. Lupus causes severe inflammation throughout the body and can have a serious impact on the lives of those affected. Researchers at the Max Planck Institute for Infection Biology in Berlin have now discovered a mechanism that can trigger lupus in children. This mechanism regulates the amount of a specific immune receptor that normally recognizes the genetic material of pathogens. If this mechanism is disrupted, receptors accumulate in the immune cells leading to the recognition of the body's own genetic material. As a result, the immune system turns against its own body and causes the systemic inflammation of lupus.

Source: Max-Plance-Gesellschaft