Case Presentation:
A 63 year old African-American Male with a history of well-controlled hypertension and hyperlipidemia presented with a four day history of new-onset lower extremity, upper extremity, and abdominal swelling. He denied shortness of breath, chest pain, orthopnea, and constitutional symptoms, but did report occasional non-drenching night sweats. He reported being otherwise healthy with no known history of baseline liver or kidney disease, but sought evaluation at the suggestion of his spouse who noticed the swelling. Vital signs were within normal limits. Physical exam was significant for abdominal distension with mild ascites and shifting dullness, 3+ pitting edema in the lower extremities to the level of the knees, decreased breath sounds in the left anterior lung fields, and mild jugular venous distention. There was no lymphadenopathy or testicular masses and neurologic examination was within normal limits. Laboratory values were indicative of renal failure with nephrotic range proteinuria. A 13x9x10 cm anterior mediastinal mass was incidentally found on chest x-ray. Subsequent CT without contrast detailed extension of the mass from the left brachiocephalic vein to the left ventricle, abutting the aorta, though MRI showed no apparent extension into surrounding structures. Fine needle aspiration confirmed a large thymoma. Renal biopsy was consistent with minimal change disease likely secondary to the malignancy. Despite aggressive diuresis and high dose steroids, renal function continued to decline leading to initiation of hemodialysis. Hospital course was complicated by recurrent left sided pleural effusions, twice requiring thoracentesis and chest tube placement. The patient ultimately underwent an uncomplicated median sternotomy and extended thymectomy with a left lung wedge reduction due to tumor adherence. Unfortunately, the patient’s renal function did not improve after resection and he continued to require outpatient dialysis.
Discussion:
This case depicts a rare presentation of thymoma-associated paraneoplastic glomerulonephritis, specifically manifesting as minimal change disease (MCD). Although an uncommon occurrence, MCD is the most frequent thymoma-associated glomerular lesion and its pathogenesis is linked to an altered immune response of T-cells. MCD associated with lymphocyte-predominant thymoma typically responds well to steroids, however, this patient did not respond. It is important to note that even with thymectomy, patients can continue to exhibit nephrotic syndrome with progressive renal decline, an association that is related to persistent T-cell dysfunction after tumor removal. Additional studies have shown that thymomas are chemosensitive diseases, therefore this case highlights the need for further investigation of chemotherapy in the management of paraneoplastic glomerulonephritis. Of importance, an emphasis on early detection of nephrotic syndrome, initiation of appropriate therapy, and pursuit of a multidisciplinary approach may prevent the progression to end-stage kidney disease.
Conclusions:
Nephrotic syndrome in an otherwise healthy adult patient should be a red flag for possible malignancy. More specifically, thymomas are known to cause minimal change disease as a paraneoplastic syndrome. Even with surgical excision of the offending tumor, however, renal failure can progress due to persistent T-cell dysfunction.