Histological transition from minimal change disease to THSD7A-associated membranous nephropathy in a patient receiving long-term steroid treatment: A case report

RATIONALE: A predominant Th2 immune response is suggested in the pathogenesis of both minimal change disease (MCD) and membranous nephropathy (MN); however, consecutive development of the 2 diseases in a patient is extremely rare. PATIENT CONCERN: A Japanese man, who developed nephrotic syndrome in his 50s and was diagnosed with MCD by renal biopsy, experienced a relapse of proteinuria approximately 3 years later during long-term steroid treatment. Since the proteinuria was resistant to increase in steroid dosage, repeat renal biopsy was performed, which revealed a small amount of glomerular subepithelial immune deposits containing immunoglobulin (Ig)G (dominantly IgG4). Immunostaining for thrombospondin-type-1-domain-containing-7A (THSD7A) was positive on the glomerular capillary walls, whereas that for other causative antigens of MN, such as phospholipase A2 receptor or neural epidermal growth factor-like 1 protein, was negative. Detailed examination found no associated condition, including malignancies and allergic diseases. DIAGNOSIS: The diagnosis of THSD7A-associated idiopathic MN was made. INTERVENTIONS AND OUTCOMES: He received further increased dose of steroids. Thereafter he maintained clinical improvement because his urinary protein level was decreased. LESSONS: The present case suggested that histological transition from MCD to MN is possible and repeat biopsy would be crucial for accurate diagnosis.