Membranous nephropathy associated with thrombospondin type-1 domain-containing 7A (THSD7A) in an adult woman with eosinophilia.

A 30-year-old woman on steroid therapy for eosinophilia presented with nephrotic syndrome during steroid tapering. She was diagnosed with membranous nephropathy (MN) stage II-III (positive for IgG1 and IgG4) by renal biopsy. There was no evidence of secondary MN. Her urinary protein level was controlled to 0.5 g/day or less, and her eosinophil count in white blood cell differential was stabilized at less than 10% without increasing the steroid dosage. The renal specimen did not show any enhanced granular expression of PLA2R along the glomerular basement membrane, and PLA2R was not detected in the patient's serum. On retrospective analysis, enhanced granular staining for thrombospondin type-1 domain-containing 7A (THSD7A) in the glomeruli was detected in the biopsy, and anti-THSD7A IgG was detected in the serum using a commercial indirect immunofluorescence test (IFT). Based on these, the case was considered as THSD7A-associated MN with comorbid eosinophilia. The causal relationship between THSD7A-related MN and eosinophilia was unclear. However, a few cases of THSD7A-associated MN with eosinophilia have been reported, and further clarification on the relationship between THSD7A-related MN and eosinophilia is warranted.