case_images: PMC11298385_01
case_images: Case 1: A 37-year-old woman experienced hemophagocytic lymphohistiocytosis 20 days after her diagnosis of autoimmune encephalitis. A 37-year-old lady was admitted to our hospital with headache and vomiting for 1 month. Her serum and cerebrospinal fluid were positive for anti-neuron antibodies. On enhanced MRI, there were high signals in the cortex of the left occipital lobe [(B), day 34, arrow] and enlarged cerebral sulcus vessels. She was diagnosed as a case of autoimmune encephalitis. On the 54th day, her platelet count suddenly dropped, and other examinations, such as bone marrow biopsy, supported lymphoma-associated hemophagocytic lymphohistiocytosis (A). On the 84th day, the enhancement remained in the cortex of the left occipital lobe [(B), day 84]. The counts of platelet, hemoglobin, and neutrophils recovered after the administration of R-CHOP protocol (A). On the 280th day, lesions with high metabolism in the left occipital lobe were found on PET-CT, and methotrexate was administrated [(B), day 280], but headache recurred a month later [(B), day 310]. After MTX protocol and autologous stem cell transplantation, the lesions reduced without new ones on imaging at follow-up [(B), last follow-up]. The details are discussed in the main text.
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case_images: T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR), and enhancement sequencing revealed a high signal intensity in the cortex of the left occipital lobe and enlarged cerebral sulcus vessels ( Figure 1 ). The fluctuations in hemoglobin, platelets, and neutrophils are shown in  Figure 1 . During the 7-month R-CHOP administration, her symptoms improved, with no significant changes on head MRI ( Figure 1 ). However, a month later, the headache recurred, and the lesion in the left occipital lobe was found to be enlarged ( Figure 1 ).
case_images: PMC11298385_02
case_images: Case 2: A 63-year-old woman experienced hemophagocytic lymphohistiocytosis 90 days after her diagnosis of autoimmune encephalitis. A 63-year-old woman was admitted to our hospital with paroxysmal facial convulsions for 10 days. Her serum and cerebrospinal fluid were positive for anti-CASPR2. The MRI result showed multiple abnormal signals in the bilateral temporal insula [(B), day 10]. On the 100th day, the symptoms recurred, and her counts of platelet, hemoglobin, and neutrophils dropped and the other examinations such as bone marrow biopsy supported hemophagocytic lymphohistiocytosis (A). On MRI, the previous lesions shrank with old hemorrhagic foci, but new abnormal signals were found in bilateral paracingulate gyrus [(B), day 100]. The lymphoma was finally confirmed 6 months later, but the lesions had decreased with foci of malacia, and no new lesions were found on MRI [(B), day 280]. The details are discussed in the main text.
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case_images: The MRI results showed multiple abnormal signals in the temporal insula bilaterally ( Figure 2 ). Fluctuations in hemoglobin, platelets, and neutrophils are shown in  Figure 2 . On MRI, the previous lesions had shrunk with old hemorrhagic foci, but new abnormal signals were found in the bilateral paracingulate gyri ( Figure 2 ). After 1 month of chemotherapy, no seizures were observed, the symptoms improved, and the abnormal signals decreased on MRI ( Figure 2 ). Furthermore, the lesions with foci of malacia decreased in size, and no new lesions were found on MRI ( Figure 2 ).
case_images: PMC11298385_03