IgG4-related tubulointerstitial nephritis associated with only lymphadenopathy and without elevated serum IgG4 or renal imaging abnormalities: a case report and literature review.

IgG4-related tubulointerstitial nephritis (IgG4-TIN) is the most common renal manifestation of IgG4-related kidney disease (IgG4-RKD) and may cause acute or chronic renal dysfunction. Imaging often shows heterogeneous densities in the kidneys, such as a mass or multiple nodules. Serology usually demonstrates high levels of serum IgG4 and total IgG. Most patients have other organs involvement by IgG4 related disease. Although lymphadenopathy is frequently observed in patients with IgG4-TIN, it is rarely presented as the only extrarenal lesion. Herein, we present a rare case of IgG4-TIN associated with only lymphadenopathy and without elevated serum IgG4 or renal imaging abnormalities. A 61-year-old Chinese man was admitted to our hospital with seven months history of generalized lymphadenopathy and five months history of renal dysfunction. His renal imaging was normal. He had no current or previous clinical, radiographic, and/or histologic evidence of other organ involvement except for the lymphadenopathy. Renal biopsy indicated plasma cell-rich TIN with an increased number of IgG4-positive plasma cells and storiform fibrosis. Repeated lymph nodes biopsy revealed IgG4-related lymphadenopathy. However, he did not have elevated serum IgG4 or total IgG levels. Oral prednisone therapy improved his renal function and lymphadenopathy. These findings supported our final diagnosis of IgG4-TIN. Clinicians should be aware of this condition and steroid therapy should be considered for such patients. An early diagnosis and appropriate therapy can induce remission and preserve renal function.