Background Primitive neuroectodermal tumors are extremely rare and highly aggressive malignant small round cell tumors that arise from the primitive nerve cells of the nervous system or outside it. These tumors share similar histology, immunohistologic characteristics, and cytogenetics with Ewing’s sarcoma. Peripheral primitive neuroectodermal tumors of the chest wall are rare malignant tumors seen in children and young adults. Case presentation We report a rare case of peripheral primitive neuroectodermal tumor in a 4-year-old Albanian girl with a mediastinal tumor and an unusual clinical presentation. She was initially treated for acute polyradiculoneuritis (Guillain–Barré syndrome) owing to pain, weakness in the lower limbs, and walking difficulty, as well as severe irritability. During the second week of treatment, the child began to experience dry cough, chest discomfort, and worsening dyspnea. Chest radiography, chest computed tomography, and contrast-enhanced computed tomography demonstrated a large mass in the right hemithorax that was derived from the posterior mediastinum with expansive growth in all directions and that shifted the mediastinal structures in the anterolateral left direction. Consequently, histopathology and immunohistochemical examination of the markers S-100, CD99, and Ki-67 showed that the tumor cells stained positively for S-100 and CD99. The proliferative index measured by Ki-67 was approximately 20%, which suggested primitive neuroectodermal tumor. Conclusions Even though other diseases, including leukemia, lymphoma, and neuroblastoma, may be accompanied by musculoskeletal manifestations in children, other solid tumors, such as peripheral primitive neuroectodermal tumors, should be considered in the differential diagnosis in any child presenting with musculoskeletal symptoms.

Background As the coronavirus disease 2019 infections are still ongoing, there is an increasing number of case reports and case series with various manifestations of life-threatening multisystem inflammatory syndrome in children . Our case aims to remind all providers to scrutinize for clinical manifestations, including neurological symptoms, which may mimic aseptic meningitis. Case presentation A 5-year-old Albanian male child with obesity was admitted to the pediatric intensive care unit due to persistent fever, headache, vomiting, abdominal pain, mucocutaneous manifestations, and fatigue. Initial laboratory results revealed high level of inflammatory markers, including C-reactive protein of 156.8 mg/l, erythrocyte sedimentation rate of 100 mm/hour, procalcitonin of 13.84, leukocytosis with neutrophilia, and lymphopenia. Liver and renal functions, and capillary blood electrolytes (Na, K, Ca), were also altered. Cerebrospinal fluid was slightly turbid, with a white blood cell count of 128/mm3 (80% mononuclear cells and 20% polymorphonuclear), consistent with aseptic meningitis. The clinical presentation with prolonged fever, multiorgan dysfunction, and elevated inflammatory markers, with no plausible alternative diagnosis, matches the case definition of multisystem inflammatory syndrome in children. Combining corticosteroid methylprednisolone with intravenous immunoglobulin was effective. Conclusions Apart from the most common presentation of multisystem organ dysfunction, neurological manifestations of multisystem inflammatory syndrome in children such as aseptic meningitis, may be present as an immune response post-viral to coronavirus disease 2019. Given the rapid deterioration of children with multisystem inflammatory syndrome, early treatment with immunoglobulins and corticosteroids should be considered.