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 joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involv ...

), or on a

prosthetic heart valve An artificial heart valve is a one-way valve implanted into a person's heart to replace a heart valve that is not functioning properly (valvular heart disease). Artificial heart valves can be separated into three broad classes: mechanical hear ...

. 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. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

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

panniculus Panniculus, often incorrectly referred to as pannus, is a medical term describing 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 st ...

(a hanging flap of tissue).

Pannus in rheumatoid arthritis

The term "pannus" is derived from the Latin for "tablecloth". Inflammation and exuberant proliferation of the synovium leads to formation of pannus and destruction of cartilage, bone, tendons, ligaments, and blood vessels. Basically, the hypertrophied synovium is called pannus. 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 loss of

bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

and

. From Autoimmunity and Disease by Harley Y. Tse and Michail K. Shaw:

Pannus in ophthalmology

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

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

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

. In normal individuals, the cornea is

avascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

. Chronic local

hypoxia Hypoxia means a lower than normal level of oxygen, and may refer to: Reduced or insufficient oxygen * Hypoxia (environmental), abnormally low oxygen content of the specific environment * Hypoxia (medical), abnormally low level of oxygen in the tis ...

(such as that occurring with overuse of

contact lenses Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic ...

) 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 differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

s, such as

aniridia Aniridia is the absence of the iris, a muscular structure that opens and closes the pupil to allow light into the eye. It is also responsible for eye color. Without it, the central eye appears all black. It can be congenital, in which both eye ...

. It is often resolved by

peritomy A peritomy is a procedure carried out during eye surgery, where an incision is made at the limbus in order to reflect the conjunctiva and Tenon's capsule of the eye, usually to expose the sclera and/or extraocular muscles for a variety of sur ...

References

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