Fibrosis, arranged at least focally in a "storiform" pattern. "Storiform" is commonly referred to as meaning having a cartwheel pattern, but its literal meaning is the appearance of a woven mat [Latin: storea] (of rush or straw). Obliterative phlebitis. The venous channels are obliterated by a dense lymphoplasmacytic infiltrate, within both the venous walls and the lumen.Other histopathological features associated with IgG4-RD are:

Phlebitis without obliteration of the lumen. Tissue has increased numbers of eosinophils. Submandibular gland research
In an article from 1977, histological research into 349 cases of Küttners tumor (now known as IgG4-related sialadenitis) identified four distinct stages of the fibroinflammatory process:
Stage 1: Focal periductal (around the salivary ducts) infiltration of lymphocytes
Stage 2: Diffuse infiltration of lymphocytes and severe periductal fibrosis (scarring around the salivary ducts)
Stage 3: Prominent infiltration of lymphocytes, atrophy of parenchyma (i.e. loss of functional areas due to shrinkage), and periductal sclerosis (scarring resulting in hardening around the salivary ducts)
Stage 4: Marked loss of and sclerosis (hardening) of the parenchyma (functional area) - similar to the process involved in cirrhosis where there is shrinkage and loss of functional areas of the liverThis may reflect the inflammatory process and development of fibrosis that occurs in other organs involved in IgG4-RD. Diagnosis
Diagnosis requires tissue biopsy of an affected organ with characteristic histological findings. Serum immunoglobulin G4 is often elevated but this is not always the case. Treatment
The goal of treatment is the induction and maintenance of remission so as to prevent progression of fibrosis and organ destruction in affected organ(s).
Interstitial keratitis (IK) is corneal scarring due to chronic inflammation of the corneal stroma. Interstitial means space between cells i.e. corneal stroma which lies between the epithelium and the endothelium. Keratitis means corneal inflammation. Signs and symptoms
Acutely, early symptoms include a painful, photophobic, red watery eye. This is due to active corneal inflammation resulting in vascular invasion and stromal necrosis which can be diffuse or localized. This causes the pinkish discoloration of what was a clear transparent normal corneal tissue (called Salmon patch of Hutchinson).Such vascularization is likely to result in blurring of vision secondary to corneal stromal scarring, the presence of ghost vessels, and thinning of the cornea, especially if it involves the visual axis. Cause
By far the most common cause of IK is syphilitic disease. However, there are two possible causes of the corneal inflammatory response: an infection and/or an immunological response, such as a hypersensitivity type reaction, or (rarely) Cogan syndrome. Infectious causes include syphilis (commonest), followed by other bacterial infections (TB, Leprosy and Lyme disease) and parasitic infections (Acanthamoeba, Onchocerciasis or river blindness, Leishmaniasis, Trypanosoma cruzi or Chagas disease, Trypanosoma brucei or African sleeping sickness and microsporidia)

Pathophysiology
The corneal scarring is the end result of the initial invasion of blood vessels into the corneal stroma as part of the inflammatory response.