A 14-year-old boy presented to the Children's Hospital, Zhejiang University School of Medicine, with main complaints of recurrent abdominal pain accompanied by fever for 14 days. He had middle and upper abdominal pain on day 1 of presentation, accompanied by vomiting and diarrhea. He was diagnosed with acute gastroenteritis at a local clinic, and the symptoms relieved after being administered with intravenous cefuroxime and anisodamine. On day 2 of presentation, his abdominal pain worsened and localized at the right lower abdomen. He also had a low-grade fever, with a temperature of 38.0  C. Thus, he went to Shaoxing People's Hospital, and physical examination showed obvious pressing pain at McBurney's point at the right lower abdomen. B-ultrasound examination revealed appendicitis (diameter 6 mm) and several lymph node echoes in the right lower abdomen, the largest size of which was 21 x 10 mm. The surgeon considered it was acute appendicitis, and an emergency laparoscopic operation was performed. During the operation, about 10 ml of light yellow transparent liquid was sucked from the ileocecal junction. The normal appendix and swollen lymph nodes in dark red were found in the operative field (Figure 1). Lymphadenectomy, as well as appendectomy, was performed for pathological examination. After the operation, intravenous cefotiam and metronidazole were prescribed empirically, and symptom of abdominal pain was relieved. Since day 3 postoperation (day 5 of presentation), his temperature decreased to near normal level. The pathological examination indicated almost normal appendix and necrotizing lymphadenitis (Figure 2). The patient was discharged from Shaoxing People's Hospital on day 6 postoperation (day 8 of presentation) with body temperature at 37.7  C.
After discharge, the boy had low-grade fever accompanied by mild abdominal pain occasionally. Since day 10 of presentation, his body temperature rose to as high as 39.4  C. Intravenous ceftriaxone for 4 days was prescribed in a local clinic, and his symptoms did not improve at all.
As a result, the boy was moved to the Children's Hospital, Zhejiang University School of Medicine. During the course of his illness, he had poor appetite and sleep. He had no past medical history, and his parents denied familial inherited disease. Physical examination on admission finding includes the following: temperature of 38.6 C, heart rate at 100 number/minute (n/min), respiration at 24 n/min, blood pressure at 117/90 mmHg, weight of 53 kg, and height at 170 cm. Enlarged lymph nodes without tenderness were found in the cervical, axillary, and inguinal area. The size of the largest one was 15 x 10 mm. Heart and lung exams were normal. No abdominal tenderness was evoked during abdominal examination. The liver and spleen were not palpable. The diagnoses were KFD and postoperative appendectomy. After admission, the results of the PPD test, mycoplasma antibodies detection, tuberculosis T-SPOT test, and autoantibody test were all negative. The level of procalcitonin in serum was normal. On the fourth day after admission (on day 17 of presentation), the patient agreed to receive intravenous methylprednisolone, and his body temperature dropped to normal at the same day. After being treated with methylprednisolone for 5 days (intravenous for 3 days, 1 mg/(kg/d), twice a day; oral for 3 days, 0.5 mg/(kg/d), twice a day), he was discharged without any symptoms. He completed therapy with methylprednisolone according to the doctor's advice, including oral methylprednisolone 6 mg twice a day for 3 days, 6 mg once a day for 3 days, and 2 mg once a day for 7 days. He was followed up for 2 years after discharge, and no similar symptoms or abnormal laboratory findings recurred. The laboratory findings of the patient during the course of illness are shown in Table 1.