Renal thrombotic microangiopathy induced by β-interferon.

Sir,

We read with interest the recent case report ‘Minimal change disease with interferon-β therapy for relapsing remitting multiple sclerosis’ [1]. In this paper, the authors include renal thrombotic microangiopathy (TMA) among rare side effects of interferon (IFN) therapy, more frequently described with IFN-α [2]. We report here our experience about this topic.

A 36-year-old white female with a 3-year history of multiple sclerosis and normal blood pressure and renal function was admitted for acute renal failure and pulmonary oedema. Three months previously, she started subcutaneous IFN-β-1a treatment of 22 μg thrice weekly. On admission, physical examination showed high blood pressure and severe pleuropericarditis without neurological or dermatological findings. Laboratory tests revealed microangiopathic haemolytic anaemia. Other immunological and microbiological laboratory tests were unremarkable. A renal biopsy disclosed signs of TMA; among 43 glomeruli, light microscopy revealed focal ischaemic signs and mild mesangial cell proliferation; vessel narrowing with thrombi and thickening of arteriolar walls and intimal onion skin-like swelling; light interstitial lymphomonocytic infiltration and focal tubular atrophy. Immunofluorescence showed mesangial IgM, C1q and fibrinogen staining. A diagnosis of haemolytic–uraemic syndrome was made. She was treated with transfusions, haemodialysis, plasma exchange and methylprednisolone i.v. followed by oral prednisone. Her cardiac function improved, and haematological signs progressively disappeared, but renal function did not recover. IFN-β treatment was discontinued. She is now receiving peritoneal dialysis treatment. IFN-α is known to cause a variety of renal lesions, including TMA [3,4], but to our knowledge, our observation is the first report of TMA induced by INF-β.

Editorial note: This letter had been sent to Aravindan A. et al., but we did not receive a response.

Conflict of interest statement. None declared.