Orbital Rhabdomyosarcoma in a Pediatric Patient With Costello Syndrome.

Costello Syndrome (CS) results from a germline mutation in the HRAS gene. Rhabdomyosarcoma in CS patients has arisen from various sites but not the orbit. The authors present the first case report of orbital rhabdomyosarcoma in a patient with CS. An 18-month-old male known for CS presented with progressively worsening proptosis and periorbital edema. On presentation, he had proptosis with inferolateral globe displacement, chemosis and injection. An urgent computed tomography scan revealed a left orbital mass extending from the posterior aspect of the globe to the orbital apex, and pathological examination confirmed embryonal rhabdomyosarcoma. Treatment with chemotherapy consisted of vincristine, dactinomycin, and cyclophosphamide, and received 8 cycles of photon beam radiation. Radiological surveillance up to 12 months showed no signs of recurrence or metastatic lesions. Patients with CS are at a high risk of developing rhabdomyosarcoma and clinicians should be vigilant in the context of any clinical orbital signs of disease.