<s>[INST] context: Aicular erosions on X-ray Always remember this impoant point about SLE "Erosions on joint X-ray are rare, their presence suggests a non lupus inflammatory ahropathy such as rheumatoid ahritis". This fact has been asked so many times in various exams as : ? "Non erosive ahritis is a. feature of which of the following" On the other hand erosion is a characteristic X-ray feature of Rheumatoid ahritis. The pirmnary value of radiography in patients with Rheumatoid ahritis is to determine the extent of bone erosion and cailage destruction. The radiological hallmark of rheumatoid ahritis is : Juxtaaicular osteopeniaQ - Bone erosions? - Narrowing of joint space .from loss of aicular cailage?. Proximal interphalangeal joint can be involved in both Rheumatoid ahritis and SLE. The characteristic feature of Rheumatoid ahritis is sparing of the distal interphalangeal joint. . E.S.R. can be elevated in both Rheumatoid ahritis and SLE. Some SLE cases are even positive for Rheumatoid factor. According to current Rheumatology diagnosis and treatment "SLE may he confused with other connective tissue diseases especially Rheumatoid ahritis. SLE patients may even have positive Rheumatoid factor. The usual presentation of lupus ahritis is identical to that of Rheumatoid ahritis, but SLE ahritis is rarely erosive". [/INST] question: Amiddle aged female presents with polyahritis with elevated rheumatoid factor and A.N.A. levels, which among the following will help you to differentiate rheumatoid ahritis from SLE? | options: A: Soft tissue swelling at the proximal inter phalangial joint B: Juxta aicular osteoporosis on X-ray C: Aicularerosions on X-ray D: Elevated ESR | answer: C </s>