Retroperitoneal fibrosis. Steroid treatment response seems to depend on its association to IgG4 related disease.

Retroperitoneal fibrosis (RF) is part of a rare fibrosclerotic disorder. Oral steroids are the initial treatment. Steroid combination with other immunosupressants is used in refractory cases. Steroids refractoriness has been observed in chronic cases. Some cases of RF represent a manifestation of the IgG4 related disease (IgG4-RD) that is associated to a dramatic response to steroid therapy. It is uncertain if RF́s treatment response differs according to its association with IgG4-RD. We hypothesize that RF́s treatment response to steroids depends on the association with IgG4-RD, thus, we collected and compared clinical data from 10 RF cases; 6 male, mean age 50.6 (±16.15 SD) years. Mean FU was 28 (±25.7 SD) months. According to IgG4 levels, patients were categorized as idiopathic RF (IRF n = 5) or RF-IgG4-RD (n = 5). Therapy response was categorized as complete, partial, stable disease, recurrence or non-response. Nine cases received initial therapy with prednisone; complete response was achieved in 4 RF-IgG4 RD. The remaining 5 cases (1 RF-IgG4RD and 4 IRF) underwent a 2nd line therapy; 4 prednisone + tamoxifen and 1 prednisone + azathioprine. Prednisone + tamoxifen combination achieved complete response in 1 case (RF-IgG4RD), partial response in 1 IRF; in 1 IRF case, disease remained stable and 1 did not respond. The prednisone + azathioprine treatment achieved complete response. At follow-up all patients remained stable and no recurrence was registered. These observations suggest and support the hypothesis that response to steroid monotherapy depends on the association of RF with IgG4, suggesting that IRF cases might benefit from initial combination therapies instead of steroid monotherapy.