Background: Sarcoidosis is an inflammatory disorder of unknown cause that is characterised by the presence of non-caseating granulomas in tissues, with no evidence of other known causes of granulomatous disease.
Sarcoidosis involves multiple organs, most commonly the lungs, lymph nodes, skin, and eyes, but may be clinically evident in any organ system, including the musculoskeletal system. In sarcoidosis axial skeletal and large bone lesions may resemble osseous metastases on MRI.
Clinical Perspective: The patient was followed-up with mediastinal, axillar and cervical lymphadenopathies for 3 years and used anti-tuberculosis therapy for 9 months with no improvement. He was admitted to our hospital with worsening symptoms. FDG PET-CT examination was reported as multiple metastatic lymph nodes, bone and liver metastases with unknown primary cancer. Excisional biopsy of lymph nodes and bone biopsy revealed non-caseating granulomatous inflammation. The patient also had ocular manifestations. There were no signs of cardiac and cutaneous involvement. The lesions regressed following corticosteroid therapy.
Presentation of patients are quite non-specific and depends on the systems involved. Half of the patients may be asymptomatic, whereas others show respiratory, cardiac, cutaneous, ocular, lacrimal and salivary gland involvement. Neurosarcoidosis develops in about 5% of cases and manifest as diffuse or nodular thickening and enhancement of leptomeninges [1-2].
Imaging Perspective: Musculoskeletal sarcoidosis is detected in about 5% of patients. Involvement of axial skeleton and sparing of small bones, in this case, was an uncommon form of musculoskeletal manifestation of sarcoidosis. CT demonstrates lytic lesions with or without sclerotic margins. MRI appearance is also variable, with well-defined enhancing intramedullary lesions or an infiltrative process [3].
Symmetric hilar and mediastinal lymphadenopathies and well-defined pulmonary micronodules measuring 2-5mm at subpleural regions is typical for thoracic sarcoidosis as in this case. Perilymphatic pulmonary nodules along the bronchovascular bundles, interlobular septa and interlobar fissures are other characteristic CT findings in pulmonary sarcoidosis. Irreversible pulmonary fibrosis is detected in 25% of cases [3]. This patient had bilateral axillary lymph nodes seen in approximately 10-30% of patients.
Liver, spleen, retroperitoneal and intra-abdominal lymph nodes were also affected in this patient. Autopsy series report 24-80% chance of hepatic sarcoidosis [4]. Periportal fibrosis and hepatic nodules may be detected, however, liver-related symptoms are rare.
Although imaging findings may suggest the diagnosis of sarcoidosis, histopathologic evaluation is necessary to differentiate from metastases, lymphoma and other bone marrow neoplasia.
Outcome: Sarcoidosis may have an excellent prognosis at an early stage, however it may be associated with high mortality and morbidity in advanced cases.
Take-Home Message, Teaching Points: Radiologists have an important role in diagnosis, staging and follow-up of treatment in sarcoidosis due to variable clinical presentations and multi-organ system involvement.
