Unicentric Castleman Disease Mimicking an Autoinflammatory Disorder: A Diagnostic Challenge in a Pediatric Patient With Recurrent Fever.

Unicentric Castleman disease (CD) is a rare lymphoproliferative disorder that is characterized by the enlargement of lymph nodes on the neck, mediastinum, and retroperitoneum. Herein, we present a 6-year-old female patient, referred to our medical center because of recurrent fever accompanied by cervical lymphadenopathy and elevated inflammatory markers since 3 years of age. Fever episodes lasting 1 day continued irregularly without any accompanying symptom. MEditerranean FeVer (MEFV) gene analysis showed no mutations; however, as inflammatory markers including serum amyloid A remained markedly high during attack-free periods, colchicines was initiated. The patient did not respond to maximally tolerated doses of colchicine; therefore, we added canakinumab and systemic methylprednisolone, subsequently. Unresponsiveness to 3 doses of bimonthly canakinumab and new-onset hepatosplenomegaly led us to investigate large-vessel vasculitis and malignancy; therefore, we performed Position emission tomography, which further revealed a hypermetabolic retroperitoneal solid mass. After performing the excisional biopsy, the patient has been diagnosed as suffering from hyaline vascular variant CD, confirmed by histopathology. In conclusion, we report a pediatric unicentric CD, which resembled autoinflammatory diseases and responded well to surgical resection, with the normalization of inflammatory markers 1 month after the procedure. CD, even the unicentric and hyaline vascular variant, should be considered in the differential diagnosis of the patients with an autoinflammatory phenotype.