Painless Brown Plaques on a Sarcoidosis Patient's Legs

Can you guess the cause of these skin lesions, given biopsy results and information about a comorbidity that may (or may not) be relevant?

[[{"type":"media","view_mode":"media_crop","fid":"27002","attributes":{"alt":"necrobiosis","class":"media-image media-image-right","height":"157","id":"media_crop_1822072212340","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2582","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"float: right;","title":" ","typeof":"foaf:Image","width":"228"}}]]A 59-year-old woman previously diagnosed with pulmonary sarcoidosis and diabetes mellitus presented with these asymptomatic plaques on her lower extremities.

Biopsy showed a granulomatous infiltrate of epithelioid histiocytes and multinucleated giant cells surrounded by lymphocytes “layered” throughout the dermis.

Can you guess what is causing them to develop?

Click here to read the diagnosis and full case description.