Pannus is an abnormal layer of fibrovascular tissue or

granulation tissue Granulation tissue is new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size ...

. Common sites for pannus formation include over the cornea, over a joint surface (as seen in

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...

), or on a prosthetic heart valve. Pannus may grow in a tumor-like fashion, as in joints where it may erode articular

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

and bone. In common usage, the term ''pannus'' is often used to refer to a

panniculus The panniculus (often incorrectly referred to as pannus) is a dense layer of fatty tissue consisting of excess subcutaneous fat within the lower abdominal region. Panniculi can form after rapid weight loss, as seen with strict exercise plans—i ...

(a hanging flap of tissue).

Pannus in rheumatoid arthritis

The term "pannus" is derived from the Latin for "tablecloth". Chronic inflammation and exuberant proliferation of the synovium leads to formation of pannus and destruction of cartilage, bone, tendons, ligaments, and blood vessels. Pannus tissue is composed of aggressive macrophage- and fibroblast-like mesenchymal cells, macrophage-like cells and other inflammatory cells that release collagenolytic enzymes. In people suffering from

, pannus tissue eventually forms in the

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

affected by the disease, causing bony erosion and

loss via release of IL-1, prostaglandins, and substance P by macrophages.

Pannus in ophthalmology

ophthalmology Ophthalmology (, ) is the branch of medicine that deals with the diagnosis, treatment, and surgery of eye diseases and disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a ...

, pannus refers to the growth of blood vessels into the peripheral

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

. In normal individuals, the cornea is

avascular Blood vessels are the tubular structures of a circulatory system that transport blood throughout many animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the tissues of a body. They also take waste and ...

. Chronic local hypoxia (such as that occurring with overuse of

contact lenses Contact lenses, or simply contacts, are thin lens (optics), lenses placed directly on the surface of the Human eye, eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct ...

) or inflammation may lead to peripheral corneal vascularization, or pannus. Pannus may also develop in diseases of the corneal

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...

s, such as

aniridia Aniridia is a condition characterized by the absence or near absence of the iris, the colored, muscular ring in the eye that controls the size of the pupil and regulates the amount of light entering the eye. This absence results in a primarily b ...

. It is often resolved by peritomy.

References

{{Reflist Medical terminology Pathology