As sodium level in diabetic ketoacidosis (DKA) and hyperglycemic hyperosmolar state (HHS) is usually low, normal, or slightly elevated, severe hypernatremia with DKA and/or HHS is rare. Case 1 was a 14-year-old boy, presenting with typical laboratory test values and symptoms consistent with DKA and HHS. His corrected sodium level, 172 mEq/L, might have occurred as a result of consuming 6 L/day of highly carbonated, carbohydrate-and sodium-rich drinks during the week preceding the diagnosis. This patient developed right lung artery thrombosis, which did not require treatment. Case 2 was a 10-year-old girl, presenting with typical laboratory test values and symptoms of DKA and HHS. Her corrected sodium level, 175 mEq/L, might have occurred as a result of large electrolyte-free water loss associated with osmotic diuresis. These two cases of patients presenting with DKA-HHS and severe hypernatremia are the first to be reported in Japan.

Pediatric neoplastic diseases account for about 10% of cases of fever of unknown origin (FUO), and most neoplastic disease cases are leukemia, lymphoma, and neuroblastoma. Brain tumors are rarely reported as the cause of FUO, although craniopharyngioma, metastatic brain tumor, and Castleman's disease have been reported. We report a case of intracranial mesenchymal tumor (IMT) with a FET:CREB fusion gene, which had inflammatory phenotype without neurological signs. A 10‐year‐old girl was admitted with a 2‐month history of intermittent fever and headache, whereas her past history as well as her family history lacked special events. Sepsis work‐up showed no pathological organism, and empirical antibiotic therapy was not effective. Bone marrow examination showed a negative result. Cerebrospinal fluid examination showed elevated protein as well as cell counts, and head magnaetic resonance imaging showed a hypervascular mass lesion with contrast enhancement in the left cerebellar hemisphere. The patient underwent tumor excision, which made the intermittent fever disappear. Pathological examinations resembled those of classic angiomatoid fibrous histiocytoma (AFH), but the morphological features were distinct from the AFH myxoid variant; then we performed break‐apart fluorescence in situ hybridization and confirmed the tumor harbored the rare EWSR1::CREM fusion gene (Ewing sarcoma breakpoint region 1 gene (EWSR1) and cAMP response element binding (CREB) family gene). Consequently, we diagnosed the condition as IMT with EWSR1::CREM fusion. Elevated serum concentration of interleukin 6 (IL‐6) was normalized after tumor resection, which suggested the fever could be caused by tumor‐derived IL‐6. This is the first case of IMT with EWSR1::CREM fusion that showed paraneoplastic symptoms associated with the IL‐6/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Although brain tumors are rarely diagnosed as a responsible disease for FUO, they should be considered as a cause of unknown fever even in the absence of abnormal neurological findings.

BackgroundPediatric neoplastic diseases account for about 10% in fever of unknown origin (FUO), and most neoplastic diseases cases are leukemia, lymphoma, and neuroblastoma. Brain tumors are rarely reported as the cause of FUO, although craniopharyngioma, metastatic brain tumor, and Castleman's disease have been reported. We report a case of intracranial mesenchymal tumor (IMTs) with FET-CREB fusion gene, whose had inflammatory phenotype without neurological signs.Case presentationA 10-year-old girl was admitted with 2 months history of intermittent fever and headache, whereas her past history as well as her family history lacked special events. Sepsis work-up showed no pathological organism and empirical antibiotics therapy was not effective. Bone marrow examination showed a negative result. CSF examination showed elevated protein as well as cell counts and head MRI showed a hyper vascular mass lesion with contrast enhancement in the left cerebellar hemisphere. The patient underwent tumor excision, which made the intermittent fever disappear. Pathological examinations resemble those of classic angiomatoid fibrous histiocytoma (AFH) but the morphologic features are distinct from the AFH myxoid variant, then we performed break-apart fluorescence in situ hybridization (FISH) and confirmed the tumor harbored rare EWSR1-CREM fusion gene (the Ewing sarcoma breakpoint region 1 gene (EWSR1), cAMP response element binding (CREB) family gene). Consequently, we diagnose as IMT with EWSR1-CREM fusion. Elevated serum concentration of IL-6 was normalized after tumor resection, which suggested the fever could be caused by tumor-derived IL-6.ConclusionsThis is the first case of IMT with EWSR1-CREM fusion that showed paraneoplastic symptoms associated with the IL-6/STAT3 signaling pathway. Although brain tumors are rarely diagnosed as a responsible disease for FUO, they should be considered as a cause of unknown fever even in the absence of abnormal neurological findings. (285 words)

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The authors declare no conflicts of interest.