title: Acute tubulointerstitial nephritis with severe renal impairment associated with multisystem IgG4-related disease.
abstract: The IgG4-related disease has a wide clinical spectrum where multiple organs can be affected, and the diagnosis depends on typical histopathological findings and an elevated IgG4 expression in plasma cells in the affected tissue. We describe the clinical presentation and evolution of a patient with acute tubulointerstitial nephritis, severe kidney failure and systemic manifestations such as lymphadenomegaly and chronic pancreatitis. The diagnosis was confirmed by the clinical picture and kidney and lymph node histopathology, in which immunohistochemistry of the lymphoid tissue showed policlonality and increased expression of IgG4, with a IgG4/total IgG ratio > 80%. The patient was treated with prednisone at a dose of 60 mg/day, followed by mycophenolate mofetil, and showed clinical and renal function improvement at 6 months of follow-up. The high index of suspicion of IgG4-related disease with multisystem involvement and the early treatment of this condition are essential to improve the prognosis of affected patients. Resumo A doença relacionada à IgG4 tem um espectro clínico amplo em que múltiplos órgãos podem ser afetados, e o diagnóstico depende de achados histopatológicos típicos e elevada expressão de IgG4 em plasmócitos no tecido afetado. Descrevemos o quadro clínico e a evolução de um paciente com nefrite túbulo-intersticial aguda, insuficiência renal grave e manifestações sistêmicas como linfoadenomegalias e pancreatite crônica. O diagnóstico foi confirmado pelas características clínicas e pela histopatologia renal e de linfonodo, na qual a imunohistoquímica mostrou tecido linfoide com policlonalidade e expressão aumentada de IgG4, com uma relação IgG4/IgG total > 80%. O paciente foi tratado com prednisona na dose de 60 mg/dia, seguido de micofenolato mofetil, e apresentou melhora clínica e da função renal depois de 6 meses de tratamento. O alto índice de suspeição da doença relacionada ao IgG4 com comprometimento multissistêmico e o tratamento precoce desta condição são primordiais para a melhora do prognóstico destes pacientes.
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Rafael Coimbra Ferreira
authors.initials: RC
authors.lastname: Beltrame
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Maurício
authors.initials: M
authors.lastname: Friderichs
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Bárbara Rayanne
authors.initials: BR
authors.lastname: Fior
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Pedro Guilherme
authors.initials: PG
authors.lastname: Schaefer
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Gustavo Gomes
authors.initials: GG
authors.lastname: Thomé
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Dirceu Reis da
authors.initials: DR
authors.lastname: Silva
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Elvino José Guardão
authors.initials: EJ
authors.lastname: Barros
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Renato
authors.initials: R
authors.lastname: Seligman
authors.affiliation: Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul.
authors.forename: Francisco Veríssimo
authors.initials: FV
authors.lastname: Veronese
mesh_terms: D006801:Humans; D007074:Immunoglobulin G; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000150:complications*; D010265:Paraproteinemias / Q000150:complications*; D051437:Renal Insufficiency / Q000150:complications*; D012720:Severity of Illness Index
chemical_list: D007074:Immunoglobulin G