A Case Report of Mediastinal Teratoma in a Pediatric Patient With Nephrotic Syndrome: Paraneoplastic Syndrome or Incidental Finding?

A 12-year-old female presented with weight gain, edema, and shortness of breath. Laboratory and urine studies confirmed nephrotic syndrome and presence of a mediastinal mass, identified as a mature teratoma after resection. Nephrotic syndrome persisted despite resection and renal biopsy confirmed minimal change disease, which ultimately responded to steroid treatment. She had two relapses of nephrotic syndrome after vaccination administration, both of which occurred within eight months of tumor resection and were responsive to steroids. Autoimmune and infectious workup for other causes of nephrotic syndrome was negative. This is the first reported case of nephrotic syndrome associated with mediastinal teratoma.