Melanosis coli, also pseudomelanosis coli, is a disorder of pigmentation of the wall of the colon, often identified at the time of

colonoscopy Colonoscopy () or coloscopy () is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (''e. ...

. It is benign and may have no significant correlation with disease. The brown pigment is

lipofuscin Lipofuscin is the name given to fine yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion. It is considered to be one of the aging or "wear-and-tear" pigments, found in the liver, kidney, heart muscle, retin ...

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

s, not

melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...

Cause

The most common cause of melanosis coli is the extended use of

laxative Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...

s, and commonly

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Isomers include various quinone derivatives. The term anthraquinone however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxo ...

containing laxatives such as senna,

aloe vera ''Aloe vera'' () is a succulent plant species of the genus ''Aloe''. It is widely distributed, and is considered an invasive species in many world regions. An evergreen perennial, it originates from the Arabian Peninsula, but grows wild in tro ...

, and other plant

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

s. The anthranoid laxatives pass through the gastrointestinal tract unabsorbed until they reach the large intestine, where they are changed into their active forms. The resulting active compounds cause damage to the cells in the lining of the intestine and leads to apoptosis (a form of cell death). The damaged (apoptotic) cells appear as darkly pigmented bodies that may be taken up by scavenger cells known as macrophages. When enough cells have been damaged, the characteristic pigmentation of the bowel wall develops. The condition can develop after just a few months of laxative use. However, other causes are identified, including an increase in colonic epithelial

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

Endoscopically An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

, the

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

may show a brownish discoloration in a

moiré pattern In mathematics, physics, and art, moiré patterns ( , , ) or moiré fringes are large-scale interference patterns that can be produced when an opaque ruled pattern with transparent gaps is overlaid on another similar pattern. For the moiré ...

Histologic appearance

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

, melanosis coli shows characteristic pigment-laden

s within the mucosa on PAS staining. The histologic

differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...

of mucosal pigmentation is:

(melanosis coli), hemosiderin-laden macrophages, and

(rare). Image:Melanosis path.jpg, Micrograph showing melanosis coli, which appears as brown pigmentation in the macrophages in the lamina propria. Image:Melanosis coli low mag.jpg, Micrograph of melanosis coli. H&E stain. Image:Melanosis coli intermed mag.jpg, Micrograph of melanosis coli. H&E stain.

Prognosis

No adverse effects or consequences of melanosis coli have been identified.

Relation to true melanoses

The condition is unrelated to true melanoses, such as Peutz–Jeghers syndrome and smoker's melanosis. Peutz–Jeghers syndrome causes pigmentation of the skin and mucous surfaces with

, and polyps in the digestive tract.

Non-colonic pseudomelanoses

Pseudomelanoses of other parts of the digestive tract, gastrointestinal tract have also been reported, and are of unclear relevance. Patients with colostomy, colostomies can have melanosis involving the stoma (medicine), stoma, which is also of no significance.

References

External links

{{Medical resources , ICD10 = {{ICD10, K63.8 , ICD9 = , ICDO = , OMIM = , DiseasesDB = , MedlinePlus = , eMedicineSubj = , eMedicineTopic = , MeSH = , GeneReviewsNBK = , GeneReviewsName = , Orphanet = Gastrointestinal tract disorders