[Ormond syndrome: a rare diagnosis in a patient with hypogammaglobulinemia secondary to rituximab].

Introduction: Ormond syndrome, or idiopathic retroperitoneal fibrosis, is a rare disease with an annual incidence of 0.1 to 0.4 cases per 100,000 inhabitants and a prevalence of 1.4 per 100,000 inhabitants. It primarily affects men (2-3:1), with diagnosis between 40 and 60 years of age. It is characterized by the growth of fibroinflammatory tissue in the retroperitoneum, with possible compression of vascular and urinary structures. Its diagnosis is complex and requires ruling out malignancy or other secondary causes. We present a case with a late diagnosis and referral to immunology due to hypogammaglobulinemia secondary to rituximab.

Case report: A 54-year-old male patient with chronic kidney disease on hemodialysis was diagnosed in 2006 with retroperitoneal fibrosis after findings of ureteral stenosis and periaortic masses. Biopsies were performed, ruling out malignancy and IgG4-RD. In 2023, the patient received rituximab for inflammatory reactivation, with clinical improvement, but developed severe hypogammaglobulinemia (IgG <500 mg/dL), prompting referral to the immunology department. Subcutaneous immunoglobulin was started, with clinical stabilization. A relevant prior finding was low IgG3 levels before rituximab, with no clear relationship to Ormond syndrome.

Conclusion: This case highlights the importance of considering Ormond syndrome in unexplained retroperitoneal fibrosis and the need for a multidisciplinary approach. It also underscores the importance of early diagnosis and close follow-up in patients with chronic fibroinflammatory disease, as well as immunological monitoring in those receiving immunosuppression, to prevent and treat associated complications. Given its rarity, it is essential to document more cases to improve understanding and management of this condition.