A 14-year-old Middle Eastern girl from Iran was admitted to Sina Medical Research and Training Hospital on 13 January 2019 because of fever and rash. She had been well until 4 weeks earlier, when she developed new-onset generalized tonic-clonic seizure with normal brain MRI and magnetic resonance venography (MRV). An electroencephalogram (EEG) showed epileptic waves; thus, she was treated with phenobarbital and lamotrigine. Since then she had no more seizures. At time of admission (4 weeks after seizure treatment), she had fever and itchy skin rash, anorexia, nausea malaise, and fatigue of 1-week duration. She was otherwise fit and well with no significant past medical history of note and no history of familial disease. On physical examination, she was alert, oriented, and conscious. She had multiple firm, non-tender, right and left cervical and inguinal lymph nodes as well as an erythematous maculopapular rash on her chest, abdomen, back, and upper limbs without palm and sole involvement that was highlighted with fever; the rash was inconspicuous when fever subsided. Lungs, heart, abdomen, extremities, and neurologic examinations were normal. There was no hepatomegaly or splenomegaly. Her vital signs on the first day of admission were: blood pressure, 105/65; body temperature, 38.7 axillary; pulse rate, 115; and respiratory rate, 20. Blood investigation immediately after admission revealed pancytopenia: white blood cells (WBC), 3140 cells/mm3; hemoglobin (Hb), 11.8 g/dl; and platelets (PLT), 118,000. Cervical and abdominal ultrasounds were done and showed multiple lymph nodes in right posterior (5 × 23 mm), anterior (4 × 25 mm) cervical triangle, posterior occipital (6 × 15 mm), submandibular (5 × 14 mm) with echogenic hilum, left posterior (4 × 8, 4 × 11, 4 × 18 mm), anterior (2 × 11, 3 × 10 mm) cervical triangle with echogenic hilum, and submandibular (3 × 14 mm) without echogenic hilum with normal size of liver and spleen. A computed tomography (CT) scan of her chest (pulmonary and mediastinal) and abdomen was normal with bilateral inguinal lymphadenopathy. Cardiac echocardiography and electrocardiography (EKG) were both normal. Laboratory workup was summarized in Tables and. Our first diagnosis was ACHS based on fever, rash, lymphadenopathy, and pancytopenia after taking anticonvulsants, so a neurology consult was done to change phenobarbital and lamotrigine to levetiracetam. Our differential diagnoses were viral infections, collagen vascular disease, Kikuchi-Fujimoto disease, and hematologic malignancy; all of which were ruled out. During her first week of hospitalization, our patient had daily intermittent fever with spikes in the mornings and at nights up to 39.5–40 °C which responded to parenteral acetaminophen. Furthermore, her lactate dehydrogenase (LDH) level increased, whereas WBC and PLT decreased. Laboratory evaluation revealed no further diagnosis. Moreover, a peripheral blood smear (PBS), which was reported by an oncologist, was normal without malignancy. On the eighth hospital day, she underwent cervical lymph node excisional biopsy with respect to oncologist’s recommendation and she was given chlorpheniramine 4 mg every 12 hours after returning from the operating room. The next day, her fever and rash completely resolved and she got well. A brief report of the lymph node biopsy by the pathologist was as follows: Two lymph node tissues with architectural distortion and depletion in germinal centers and diffuse infiltration of the histiocytes in the parenchyma and some mature lymphocytes. Two vague granuloma formations composed of epithelioid cells aggregate, surrounded by a rim of lymphocytes were noted. There were a few (scattered) large cells with vesicular nuclei and high nuclear cytoplasmic (N/C) ratio, which were more probably immunoblasts. There were also foci of necrosis and necrotic debris in the background. Therefore, immunohistochemistry (IHC) was recommended. The IHC results for PAX5, CD5, CD30, CD68, and Ki-67 were not in favor of lymphoma. According to the pathologist’s point of view, necrotizing lymphadenitis was a possible diagnosis. On the 16th hospital day, our patient was discharged while receiving levetiracetam and clonazepam. She was visited10 days after discharge. She had been in a good clinical condition without any problem or fever. Her latest laboratory investigation revealed: WBC, 4260 cells/mm3 (with normal eosinophil count as outlined in Table ); Hb, 12 g/dl; PLT, 267,000; LDH, 388 IU/L; erythrocyte sedimentation rate (ESR), 23 mm/hour; and C-reactive protein (CRP), negative.