Upon admission, the patient underwent continuous blood purification therapy. Cyclosporine was discontinued, and intravenous methylprednisolone (80 mg/day) was administered for 1 week. The patient’s renal function gradually improved, with urine output increasing to 1,500-2,000 mL/day. Once stabilized, dialysis was terminated, and the dialysis catheter was removed.

At 1-year follow-up, a regimen of prednisone (7.5 mg, once daily), mycophenolate mofetil (250 mg, twice daily), and thalidomide (50 mg, once nightly) was in place. The most recent hematologic measures were as follows: WBC count, 1.9 × 10⁹/L; Hgb, 103 g/L; platelet count, 43 × 10⁹/L; and reticulocytes, 2.51%. CRP values had normalized, and proteinuria was absent on urinalysis, which did show 8.4 erythrocytes per high-power microscopic field. Uric acid (583 μmol/L), SCr (108 μmol/L), cystatin C (1.52 mg/L), and estimated glomerular filtration rate (eGFR, 79.15 mL/min/1.73 m²) were all within or near acceptable levels, reflecting adequacy of renal function.

BD is a chronic, relapsing, and multisystem autoimmune disorder with distinctive clinical features, including recurrent oral and genital ulcers, uveitis, and GI lesions (4). The diagnosis remains challenging due to lack of specific serologic markers, and disease severity may vary substantially among patients. Certain inflammatory cytokines, such as interleukin-6 (IL-6), have been proposed as auxiliary markers of disease activity (5). The sequence of events in our patient, marked by episodic oral ulcers and fever, diagnosis of MDS, catastrophic intestinal bleeding, seizure activity, acute renal failure, hyperkalemia, and obligatory temporary pacemaker implantation, was especially complex and overall proved quite daunting for clinical management.

The reported prevalence of renal involvement in BD varies widely across studies, ranging from 0-55% (3). These data may reflect differences in study populations, geographic regions, genetic predispositions, and diagnostic criteria, all of which influence accuracy and consistency of prevalence estimates. Abnormal urinalysis (i.e., proteinuria and microscopic hematuria) is the most frequent indicator of renal injury. Elevated SCr and blood urea nitrogen levels are reported in only a minority of cases (6), A subset of patients may also present with hypertension, often exhibiting malignant hypertension secondary to BD-related renal artery stenosis (7, 8). Histologic findings in renal biopsies from patients with BD have exposed an array of disease processes. Renal amyloidosis is most commonly reported, followed by chronic glomerulonephritis; and although rare, IgA nephropathy has been documented as well (9–11).

Acute tubulointerstitial injury is an uncommon manifestation of BD. To date, this is the first reported case of BD to show concurrent ATN and IgA nephropathy in the setting of MDS. As a chronic, relapsing autoimmune disorder, BD typically calls for long-term immunosuppressive therapy using corticosteroids, conventional immunosuppressants, or biologic agents. However, a number of these are actually implicated in renal injury. Prolonged use of cyclosporine is associated with acute and chronic tubulointerstitial injury, including interstitial fibrosis (12). Biologic agents, such as adalimumab and infliximab, have also been linked to onset and progression of IgA nephropathy in some patients (13, 14). Rarely, BD-related acute kidney injury (AKI) may be pronounced, causing rapid elevations of SCr and life-threatening hyperkalemia. It is exceedingly rare for patients with BD to require both temporary cardiac pacing and CRRT, as we have detailed.

In our patient, calamitous GI bleeding created a surgical emergency. Still, intestinal resection and the functional impairment entailed are recognized risk factors for secondary oxalate nephropathy. Inflammatory bowel disease is known to increase intestinal binding of calcium to the surplus of unabsorbed fatty acids produced, thereby reducing fecal excretion of calcium oxalate. Hyperoxaluria is thus promoted through enhanced oxalate absorption. At this same time, decreased urinary excretion of citrate and magnesium—both inhibitors of calcium oxalate crystallization—further increases the risk of nephrolithiasis. Hence, intestinal surgery (ileostomy mostly) is an independent risk factor for urinary stone formation, due to chronic dehydration, bicarbonate loss, and resultant urine acidification (15).

Upon histologic examination, renal tubules in this patient harbored apparent oxalate deposits. Disc-shaped crystals showing white birefringence under polarized light were visible within the lumina, possibly contributing to tubular obstruction and exacerbating the acute kidney injury ( Figure 4 ). In previously reported cases of BD-related renal compromise, glomerular pathology occasionally revealed crescent formation, which is associated with rapid disease progression and poor urinary outcomes (3, 16). However, glomerular involvement was mild in this instance, with renal injury largely confined to ATN and interstitial inflammation. Corticosteroid therapy is known to accelerate recovery from ATN. In addition to high-dose corticosteroids, CRRT likely helped to improve renal function.

Intestinal effects are inherent in BD, compelled by the systemic inflammatory nature of this disorder (17). Pertinent clinical symptoms commonly include abdominal pain, diarrhea, and hematochezia. In more severe cases, intestinal obstruction, perforation, or necrosis may emerge as complications. Management strategies for such involvement rely on both pharmacologic and surgical interventions. Immunosuppressive therapy, namely corticosteroids and calcineurin inhibitors, remain the cornerstone of medical treatment, aiming to control inflammation and alleviate GI symptoms (12). For disease refractory to conventional immunosuppressants, surgical remedies (ie, bowel resection and enterostomy) may be inevitable. Biologic agents targeting tumor necrosis factor-alpha (TNF-α), particularly infliximab and adalimumab, have demonstrated efficacy in those with intractable intestinal BD, facilitating symptom control and healing of extreme mucosal damage (18). Our patient’s uncontrolled GI bleeding and necrosis did not respond to therapy (corticosteroids, IV immunoglobulin, thalidomide, and cyclosporine), rendering surgical resection and ileostomy unavoidable. Infliximab administration in the aftermath finally brought clinical improvement and resolution of GI symptoms.

The coexistence of BD and MDS represents a clinically significant entity characterized by overlapping pathophysiology. MDS comprises heterogeneous clonal hematopoietic stem cell disorders featuring ineffective hematopoiesis, peripheral cytopenia, and risk of leukemic transformation. Notably, epidemiologic studies report a 0.4-3.1% prevalence of MDS among BD patients (19–21), suggesting potential bidirectional pathogenetic links. Chronic immune dysregulation inherent to BD may drive clonal expansion of hematopoietic stem cells, while MDS-related immunosuppression can manifest as BD-like features including recurrent mucocutaneous ulcers. This clinical convergence complicates diagnosis and often delays appropriate intervention, particularly given the heightened gastrointestinal involvement observed in concurrent BD-MDS cases compared to isolated BD.

Central to this interplay may be trisomy 8, a cytogenetic aberration present in 7–9% of MDS patients with detectable chromosomal abnormalities (22, 23). Mechanistically, trisomy 8 drives overexpression of proinflammatory cytokines including transforming growth factor-β, IL-6, and interleukin-7 receptor in MDS (24), mirroring elevated IL-6, granulocyte colony-stimulating factor, and TNF-α levels in trisomy 8-positive BD patients. This shared cytokine dysregulation disrupts immune homeostasis, damages hematopoietic stem cells, and promotes both bone marrow failure and autoinflammatory manifestations. Critically, trisomy 8 constitutes a high-risk marker for BD-to-MDS progression (25) and correlates with severe gastrointestinal involvement. Systematic evidence confirms trisomy 8-positive patients exhibit significantly higher mortality (OR 11.74), gastrointestinal manifestations (76.1% vs. 17.2% in classical BD), and treatment-refractory inflammation, underscoring its distinct clinico-pathologic identity (26).

Therapeutic implications emerge from this unified pathogenic model: hematopoietic stem cell transplantation demonstrates disease-modifying potential in BD patients with concurrent trisomy 8-positive MDS (27), while conventional immunosuppressants and corticosteroids remain first-line options. Future research should clarify precise molecular pathways linking trisomy 8, cytokine networks, and hematopoietic clonality to optimize risk stratification and targeted therapies.

MDS is a serious but rare clonal hematopoietic disorder. Assorted renal pathologies documented in conjunction with MDS include acute tubulointerstitial nephritis, ANCA-negative pauci-immune necrotizing and crescentic glomerulonephritis, membranous nephropathy, and IgA nephropathy (28–30). Among these, acute tubulointerstitial nephritis and membranous nephropathy are most common. Because the risk of renal biopsy is heightened in patients with MDS (due to cytopenia), biopsy proven cases are scarce. Past reports have thus failed to properly record simultaneous occurrences of BD, MDS, and renal pathology. The present account is the first to address coexistence of these three conditions, highlighting an unusual and complex clinical scenario.