Osseous sarcoidosis
Sarcoidosis is a systemic granulomatous disease characterized by non-caseating granulomas accompanied by Langhans giant cells. The lungs, lymph nodes and the skin can be affected, less commonly the bones (prevalence about 10 %). A history of systemic sarcoidosis such as respiratory symptoms or skin lesions can guide suspicion towards osseous involvement. Diagnosis of osseous sarcoidosis involves a combination of clinical evaluation, imaging studies, and sometimes biopsy.
In the toes, sarcoidosis may lead to localized pain, swelling, or decreased mobility, that can significantly impact a patient's quality of life. However, many patients remain asymptomatic.
On imaging studies, osseous manifestation of sarcoidosis typically presents as lytic lesions or cystic changes in the bones. In the toes specifically, these lesions may present as lytic changes at the phalangeal heads or shafts:
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Cystic bone lesions: Multiple small bone cysts are found, lined up close together like a row of picket fences. Due to their close proximity, the cysts occasionally form a heart shape. The cortex can be thinned out or appear moth-eaten.
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Soft Tissue Swelling: Accompanying edema around affected bones may be observed.
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MRI is useful for assessing soft-tissue involvement and marrow edema associated with bone lesions. The affected areas are hyperintense on T2-weighted images and contrast-enhancing.
Generalized involvement of osseous sarcoidosis is called “osteitis multiplex cystoides” (Juengling’s disease) presenting with multiple cystic bone lesions throughout the skeleton.
Differentiating sarcoid lesions from metastatic disease, osteomyelitis and other granulomatous diseases (e.g., tuberculosis) is crucial due to their similar radiological appearances. Biopsy of the bone lesion is considered the gold standard when there is uncertainty.
Systemic therapy with glucocorticoids or TNF-α antagonists may be indicated for symptomatic patients.
