18F-FDG PET/CT in diagnosis and response evaluation in an unusual case of antisynthetase syndrome presenting as pyrexia of unknown origin

Abstract

Anti-histidyl (Jo-1) antibodies have been implicated in the pathogenesis of anti-synthetase syndrome (ASS). A case is presented of a 55-year-old male patient presenting with pyrexia of unknown origin and inconclusive routine investigations. ¹⁸F-FDG PET/CT was performed to locate any abnormal focus, which showed increased FDG uptake in the proximal shoulder muscles, as well as lung lesions. Subsequent investigation showed the presence of anti Jo-1 antibody, and diagnosed as an anti-synthetase syndrome. The patient was successfully treated with glucocorticoids and cyclophosphamide, and the response was assessed with symptomatic relief and disappearance of FDG uptake in lung and muscle lesions on post-treatment FDG PET/CT.

Resumen

Los anticuerpos antihistidil (Jo-1) están implicados en la patogenia del síndrome antisintetasa. Presentamos un varón de 55 años con fiebre de origen desconocido y exploraciones de rutina no concluyentes. La ¹⁸F-FDG PET/TC, realizada para la localización de un foco patológico mostró, un aumento de la captación de FDG en la musculatura proximal de los hombros y en lesiones pulmonares. La investigación posterior demostró la presencia de anticuerpos anti Jo-1 y se diagnosticó un síndrome antisintetasa. El paciente fue satisfactoriamente tratado con glucocorticoides y ciclofosfamida. La respuesta se evaluó por el alivio sintomático y por la desaparición de la captación de FDG en las lesiones pulmonares y musculares demostrada en la ¹⁸F-FDG PET/TC postratamiento.