[Minimal change nephrotic syndrome complicated with recurrence of malignant thymoma: an interesting case with remission due to steroid therapy of both nephrotic syndrome and thymoma].

A 65-year-old man was admitted to our hospital with abdominal fullness and leg edema in April 2005. Diabetes mellitus and hypertension that had been diagnosed in 1990 were well-controlled with oral hypoglucemic drug. He presented with malignant thymoma accompanied by multiple metastases in the right thoracic space in December 2000. He was treated with total thymectomy, combined with chemotherapy (cisplatin + vinorelbin) and hyperthermia. This strategy obviously reduced the tumor mass. However, CT scans showed multiple recurrences of thymoma in December 2004 and abdominal fullness and leg edema appeared shortly thereafter. Laboratory findings revealed proteinuria (over 10 g/day), hypoalbuminemia, hyperlipidemia and renal dysfunction. A kidney biopsy revealed minor glomerular abnormality. He was diagnosed with minimal change nephrotic syndrome (MCNS) complicated with the recurrence of malignant thymoma. Corticosteroid therapy was started, but dialysis was transiently required to protect against oliguric acute renal failure. Three weeks after the initiation of steroid therapy, the proteinuria was improved to less than 1.0 g/day and renal function returned to within the normal range. Subsequent corticosteroid combined with immunosuppressive therapy resulted in good control of his nephrotic syndrome (NS) without recurrence. There have been a few case reports showing NS complicated with malignant thymoma. Among these, several cases with MCNS occurred after thymectomy for malignant thymoma. Interestingly, both the thymoma mass and high pre-treatment vascular endothelial growth factor (VEGF) levels decreased as NS improved with steroid therapy. These findings suggest that VEGF also might have been associated with the onset of NS in this patient.