Oral Pigmentation (Causes of Discoloration Inside Mouth)

What is oral pigmentation?

Oral pigmentation refers to discoloration of the inner lining of the mouth (oral mucosa) from its normally pink hue. This discoloration occurs due to the deposition of different colored materials over the oral mucosa which can be of physiological or pathological in nature. Oral pigmentation may be associated with certain minor local factors or underlying systemic disease. It can be an important symptom, sometimes the first symptom, of several important and severe diseases. Therefore oral pigmentation needs to be assessed carefully by a medical professional.

Types of Oral Pigmentation

Oral pigmentation is chiefly classified in to two types

• Exogenous pigmentation
• Endogenous pigmentation

Exogenous Pigmentation

Exogenous pigmentation is a condition where pigments are sourced from external sources that either make contact with the inner mouth lining or ingested and deposited in the oral mucosa.  It arises as a result of introduction of a metal or a drug within the body through the mucous membrane, intestinal tract or skin. The exogenous pigmentation can be accidental, iatrogenic or by poisoning.

Endogenous Pigmentation

Endogenous pigmentation is discoloration from substances originating within the body. The more common pigments include melanin (skin and eye pigment), hemoglobin (pigment from red blood cells), hemosiderin (from red blood cell breakdown) and other chemicals formed within the body.

Accidental

The accidental exogenous pigmentation of oral mucosa (inner mouth lining) may be caused due injuries leading to certain external particles getting embedded in the lacerated mucous membrane and causing discolorations. Such types of injuries are commonly seen in children with broken off pencil points embedded in the gums.

The discoloration is a focal gray to black colored patch of discolored mucosa. The condition is commonly referred as ‘graphite tattoos’. Similar lesions are seen with users of tooth pastes containing charcoal or certain home remedy mouth rinses or throat gargles.

Oral Leukoplakia

Medicationle

Iatrogenic causes arise when treatment is undertaken for some reason thereby leading to oral pigmentation. The iatrogenic pigmentation of oral cavity is generally seen with metallic restorations such as dental amalgam. The lesion is commonly known as ‘amalgam tattoo’.

It may be caused due deposition of amalgam in the abraded gingiva (gum) during routine amalgam filling or due to broken pieces of amalgam embedded in the tooth socket during extraction of a tooth. The pigments are black to blue in color and may gradually increase in size. The lesion is usually located over the gum line of the lower teeth.

Mouth rinses containing chlorhexidine may also cause oral pigmentation. Quinolone, hydroxyyquinolone and amodiaquine anti-malarial drugs can lead to brown to black oral pigmentation. Minocycline, an antibiotic used in the treatment of acne and urinary tract infections (UTIs), may also lead to gray to black large localized pigmentation on the hard palate and mucous membrane of oral cavity.

Metal Poisoning

The metals leading to oral pigmentation include bismuth, mercury, lead, silver, arsenic, copper and zinc.

• Bismuth poisoning is also known as bismuthism, which is caused by bismuth containing medicinal preparations. The oral manifestation of bismuthism includes oral pigmentation known as bismuth lines. It is a blue black colored lines that appears to be well demarcated on gingival papillae. It is also accompanied with metallic taste and oral ulcers.
• In mercury poisoning, faint, diffuse and gray colored pigments are present on oral mucosa.
• Lead poisoning, commonly known as plumbism is associated with the formation of ‘burtonian lines’. It is a gray-black line present along the margins of the gums.
• Silver positioning leads to gray to bluish-violet discoloration of oral mucosa with a metallic luster.

Blue to Purple Discoloration

The blue to purple colored lesions within the oral cavity are mainly due to a blood vessel malformation and Kaposi’s sarcoma.

Blood and Vessels

Hemangioma may be congenital or traumatic in origin and is characterized by proliferation of blood vessels. The oral pigmentation appears bluish or a flat reddish blue macule (port wine stains). Dilated blood vessel of tongue known as lingual varices, also lead formation of pigmented oral lesions.

Hereditary hemorrhagic telangiectasia is a genetically inherited disease causing bluish, purple pigmentation of the oral mucosa. Hematomas (collection of blood) within the oral mucosa can also lead to elevated bluish discolorations.

Kaposi sarcoma

Kaposi sarcoma leads to the formation of pigmented lesions on the hard palate. The lesion begins as a flat red macule and eventually may involve the entire palate. Kaposi sarcoma is a rare type of cancer but has become more common in recent years due to the prevalence of HIV infection. Kaposi sarcoma is considered as an AIDS-defining illness.

Brown to Black Discoloration

• Oral melanotic macule also known as ephelis represents a focally increased synthesis of melanin, the natural pigment of the skin and eyes. Commonly seen on the vermillion border of the lips, the lesion is usually less then 1 cm in diameter. The color is brown to black and oval in shape.
• Melanoplakia is a term applied to flat, localized or widespread brownish discoloration of the oral mucosa due to increased amount of melanin. It may be related to tobacco smoking (smoker’s melanosis) or diseases like Peutz-Jeghers syndrome.
• Nevus is congenital tumor like malformation of the skin or mucous membrane caused by proliferation of melanocytes (cells that produce melanin). It can be gray, light brown, blue or black in color. Generally it appears as a flat, small lesion with regular borders and is round to oval shape.
• Melanoma of the oral mucosa can occur on the lip, anterior gum region and anterior aspect of the palate. It appears as a brown or black plaque like lesion with an irregular outline. The lesion progresses rapidly and may show zones of depigmenation.
• Addison’s disease (chronic adrenal insufficiency) causes abnormal pigmentation of the skin and mucous membranes. In the oral cavity, the most commonly involved sites are the inner lining of the cheeks followed by the gums, tongue and lips. The color of the oral mucosa varies from bluish-black to pale brown or deep chocolate-colored pigments spread over from the cheek mucosa to the corner of the mouth.
• Peutz-Jeghers syndrome (hereditary intestinal polyposis syndrome) is a disease consisting of generalized intestinal polyp formation and perioral pigmentation. The lesions appear as flat, brown to black macules present around the oral cavity and eyes. Within the mouth the cheek mucosa, gums, tongue and palate may be pigmented. The lesions tend to be present at birth as small brown macules.
• Neurofibromatosis (Von Recklinghausen’s disease) and Albright’s syndrome lead to areas of melanin pigmentation on the oral mucosa and lips. The pigmentation is referred as café-au-lait spots.
• HIV associated melanosis is seen most frequently affecting the cheek mucosa followed by gingiva (gum), palate and tongue. It is represented by diffuse, multifocal, macular brown colored pigmentation.
• Overactivity of the pituitary gland and pregnancy can lead to abnormal pigmentation of the lips and oral mucosa.
• Hemochromatosis (bronze diabetes), carotenemia and jaundice can lead to various types of pigmentation of the oral cavity.

References

1. Disorders of oral pigmentation. Medscape
2. Mouth growths. Merck

Last updated on September 23, 2018.