Hilar lymphadenopathy, development of tubulointerstitial nephritis, and dense deposit disease following Pfizer-BioNTech COVID-19 vaccination.

Despite the reports on glomerulonephritis associated with COVID-19 mRNA vaccines, no study has reported about the dense deposit disease (DDD). Here, we present a case of hilar lymphadenopathy after the COVID-19 mRNA vaccination, following which the patient developed tubulointerstitial nephritis (TIN) and DDD. A 74-year-old man received his second dose of mRNA vaccine, and on the next day, he developed fever, urticaria, and dyspnea. On further examination, he had pleural effusion and right hilar lymphadenopathies, which were improved with conservative therapy. After 48 days of the second vaccination, he developed renal dysfunction and new-onset hematuria. Light microscopy findings by renal biopsy revealed apparent mesangial cell proliferation, increased mesangial matrix in the glomeruli, and diffuse inflammatory cell infiltration in the interstitium. Immunofluorescence analysis revealed 1 + positive results for IgG and IgM, negative results for IgA, and 2 + positive results for C3 with a garland pattern on the capillary walls. Electron microscopy revealed that severe cell proliferation in the capillary rumen, and continuous, thickened, and highly dark-stained spotty dense deposits in the glomerular basement membrane; and noncontinuous spotty dense deposits in the tubular basement membrane. Based on the decrease in C3 and pathological findings, TIN accompanied with DDD was diagnosed. The mRNA vaccine might have contributed to the development of lymphadenopathies, TIN, and DDD in this case. Moreover, TIN and DDD might be associated with the activated alternative pathway induced by the mRNA vaccine.