18F-FDG PET/CT Findings of Hypereosinophilic Syndrome
A 48 year old previously well man presents with dry eyes and bilateral lacrimal gland swelling. A number of investigations were performed including a lacrimal gland biopsy, diagnostic CT of chest and abdomen, and 18F-FDG PET/CT. The lacrimal gland biopsy showed reactive hyperplasia with increased eosinophils. Diagnostic CT showed mediastinal, hilar and upper abdominal para-aortic lymphadenopathy. FDG PET/CT was performed to assess the activity of the lacrimal glands and the lymphadenopathy and showed intense lacrimal gland FDG uptake with moderate activity in mediastinal and cervical lymphadenopathy. Biopsy of a mediastinal lymph node showed non-necrotising granulomatous lymphadenitis and a presumptive diagnosis of sarcoidosis or reactive lymphadenopathy was made.
The lacrimal gland hyperplasia was treated with chlorambucil and local radiotherapy with a good clinical response. A follow-up PET/CT showed a corresponding reduction in lacrimal gland activity, but persistant FDG-avid lymphadenopathy.
Consistently high eosinophil counts on all biopsy samples and peripheral full blood examination (FBE) lead to a diagnosis of Hypereosinophilic Syndrome (HES), a lymphoproliferative disorder characterised by overproduction of eosinophils resulting in organ damage. Treatment with high dose prednisolone produced a fall in the eosinophil count.
To our knowledge, the use of FDG-PET in HES has not been previously reported. Our findings suggest a possible role of FDG-PET in the non-invasive monitoring of therapy and in surveillance for malignant transformation.