The Difficulty of Diagnosing Kikuchi-Fujimoto Disease in Infants and Children Under Six Years Old: Case Report and Literature Review

We came across a 20-month-old boy with Kikuchi-Fujimoto disease (KFD) who showed atypical symptoms that were difficult to diagnose. His symptoms were different from those experienced in common clinical KFD cases. Hence, we report his case presentation and review the literature on the difference in KFD symptoms between infants and young children (under six years of age), and school-age children (6 to 20 years). A 20-month-old boy was admitted to our hospital because of prolonged fever and an enlarged right axillary lymph node with pain. He developed erythema, which was like rubella, on the face, trunk, and upper and lower extremities. The rash soon disappeared after two days. The cervical lymph nodes were not palpable. Hepatomegaly and splenomegaly were palpable. Leukopenia and a decrease in platelets were seen in the blood count. Curiously, leukocytosis developed after leukopenia was first observed. Serology titers for several pathogens were negative. A CT scan of the lungs showed swelling of the mediastinal lymph nodes and interstitial pneumonia. The examination of a specimen of the axillary lymph node obtained by biopsy was compatible with KFD. English language reports on KFD were reviewed. Fourteen (14/335: 4.2%) cases in children under six years in addition to the current case and 321 (321/335: 95.8%) cases of school-age children (6-20 years) were found in the literature. Children of school age tend to more commonly be afflicted with KFD, which is characterized by pyrexia, leukopenia, and cervical lymphadenopathy with tenderness. Inversely, major symptoms of KFD patients under six years old were lesions of the lungs in three cases, leukocytosis in six cases, and generalized lymphadenopathy in eight cases, in contrast with symptoms of school-age children. It is concluded that leukocytosis, generalized lymphadenopathy in sites other than the cervical lymph nodes, and lesions of the lungs are characteristic symptoms of severe KFD in patients under six years old, for whom the occurrence is very rare.