Complex sentence: Xanthinuria, also known as Xanthine oxydase deficiency is a rare genetic disorder that causes a deficiency of xanthine oxidase, an enzyme necessary for converting xanthine to uric acid.
Split into simpler sentences: Xanthinuria, also known as Xanthine oxydase deficiency is a rare genetic disorder causing the accumulation of xanthine. It can be caused by a deficiency of xanthine oxidase, which is an enzyme necessary for converting xanthine to uric acid.