[Lymphadenitis possibly due to human herpesvirus 7 during methotrexate therapy for rheumatoid arthritis].

A 75-year-old woman who was treated with methotrexate (MTX) for rheumatoid arthritis was admitted to our hospital because of fever and loss of appetite. Physical examination revealed exanthems in the upper limbs and systemic lymphadenopathy. Her blood test showed elevated levels of serum lactate dehydrogenase (LDH) and soluble interleukin-2 receptor (sIL-2R). Lymph node biopsy indicated atrophic follicles, interfollicular hyperplasia, and infiltration of macrophages phagocytosing nuclear debris and T-lymphocytes. This suggested lymphadenitis associated with viral infection. Human herpesvirus 7 (HHV-7) DNA was detected in the lymphoid tissue using polymerase chain reaction. The patient was successfully treated with MTX discontinuation and short-term administration of dexamethasone. Her symptoms improved, and LDH and sIL-2R levels were normalized. Human herpesvirus reactivates in patients with immunodeficiency on MTX administration. To the best of our knowledge, this is a valuable case of lymphadenitis considered to have been caused by HHV-7.