Co-occurrence of IgA nephropathy and IgG4-Tubulointersitial nephritis effectively treated with tacrolimus: a case report

BACKGROUND: Cases of concurrent immunoglobulin A nephropathy (IgAN) and IgG4-related tubulointerstitial nephritis (IgG4-TIN) are rare and previous case reports have lacked important data. KDIGO suggests a treatment with systemic glucocorticoids in IgAN patients. Glucocorticoids are recommended as the first-line therapy for IgG4-TIN. The use of tacrolimus as a long-term maintenance treatment has not been described. We report the case of a man who developed IgAN and IgG4-TIN without abnormalities in extra-renal tissue, without renal function abnormalities or impairment as well, and was treated by tacrolimus as a long-term maintenance during 45 months follow-up. CASE PRESENTATION: A 56-year-old Chinese man first presented to our hospital with the chief complaint of foamy urine for 1 year and hematuria for 3 months, with a medical history of hypertension. Testing revealed a notable increase in serum IgG4 level without abnormalities in renal function or imaging, or in dysfunction other organs. Renal biopsy showed mesangial extracellular matrix proliferation, increased mesangial cell numbers and infiltration of plasma cells. Immunofluorescence showed mesangial positivity for IgA and C3. Immunohistochemistry staining showed widespread IgG4 and increased CD38 and CD138 expression. Electron microscopy showed immune complexes located on the tubular basement membrane. He was diagnosed with IgAN and IgG4-TIN. He received glucocorticoids, leflunomide and tacrolimus to induce remission. He was given tacrolimus as long-term maintenance treatment. When tacrolimus was temporarily withdrawn, proteinuria recurred. After resuming tacrolimus therapy, he again entered complete remission. After 45 months of therapy, he remains in complete remission and the serum IgG4 level is normal. CONCLUSIONS: The finding of concurrent IgAN and IgG4-TIN without abnormalities in renal function, imaging or extra-renal tissue is rare and their coexistence may be coincidental. Long-term treatment with tacrolimus proved effective and he has remained in remission during 45 months follow-up.