Collapsing focal segmental glomerulosclerosis in a patient with oral cavity cancer: A case report.

Rationale: Focal segmental glomerulosclerosis (FSGS) is one of the most common glomerular diseases, leading to end-stage renal disease. Among the 5 variants of FSGS, the collapsing variant is rare and has the worst prognosis. Solid and hematologic malignancies are associated with glomerular diseases, such as membranous nephropathy, minimal change disease, and FSGS. However, squamous cell carcinoma of the oral cavity is rarely associated with nephrotic syndrome, especially FSGS.

Patient Concerns: A 55-year-old woman diagnosed with oral cavity cancer presented with generalized edema with heavy proteinuria and renal dysfunction after neoadjuvant chemotherapy and wide surgical excision.

Diagnosis: Renal biopsy shows segmental or global collapse of glomerular capillaries with marked hyperplasia and swelling of overlying epithelial cells, suggesting a collapsing variant of FSGS.

Interventions: After the renal biopsy, we prescribed oral prednisolone at a dose of 1 mg/kg/day. Despite immunosuppressive treatment, renal function deteriorated, and hemodialysis was started.

Outcomes: After 23 sessions of hemodialysis and high-dose oral glucocorticoid treatment, renal function gradually improved, and oral glucocorticoid therapy was discontinued after 8 months. Currently, this patient is in a cancer-free state and has normal renal function without proteinuria.

Lessons: Unusual collapsing FSGS might be associated with neoadjuvant chemotherapy and wide surgical excision in patients with oral cavity cancer. Proper diagnostic workup, such as renal biopsy and high-dose glucocorticoid therapy, might have helped recover from nephrotic syndrome and acute renal injury in cancer patients.