Idiopathic Retroperitoneal fibrosis (RPF) is a fibro-inflammatory disease characterised by inflammation and fibrosis of retroperitoneal structures. Aetiology remains unknown but autoimmune vasculitic processes are suggested. In patients with known mixed connective tissue disease (MCTD) it has rarely been described.

Six databases were searched from inception until November 2021. Following a review of the literature only one other similar presentation has been reported.

A 43 year old male presented to the emergency department with right flank pain. Past medical history included MCTD (sjrogens syndrome (SS) and systemic lupus erythematous overlap). CT showed right hydronephrosis with periureteric inflammation and stricture. In the context of known connective tissue disease, autoimmune RPF was diagnosed. As renal function was normal ureteric stenting was not performed. Prednisolone was commenced with methotrexate. At follow up abdominal pain had resolved, US KUB displayed resolution of hydronephrosis and renal function remained normal.

The case presented describes a rare presentation of RPF in a patient with MCTD. The links between these two entities requires further exploration. A high level suspicion must be exercised in patients with known MCTD presenting with symptoms of RPF to avoid delays in treatment and thus possible surgical interventions.