Scleritis - Scleritis is a rare but emergent cause of a red eye.  It is thought to be caused by an autoimmune response that can be idiopathic, triggered by infection or trauma, or secondary to underlying autoimmune dysregulation.  In fact, it is estimated that up to half of all cases of scleritis have an underlying autoimmune disorder such as IBD, SLE, granulomatosis with polyangiitis (Wegener's granulomatosis), or scleroderma.  There are two main types of scleritis: anterior and posterior.

-Anterior scleritis: involvement of the sclera anterior to the extraocular muscle insertion.  There are three variants: Diffuse (most common and most treatable), nodular (presents with tender nodules), and necrotizing (most severe and destructive).
-Posterior scleritis: involvement of the sclera posterior to the extraocular muscle insertion.  This is rarer than anterior scleritis and difficult to detect due to its more posterior location.  It is associated with retinal detachment, angle closure glaucoma, and vision loss.  

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