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Black Bone Eye Disease

The human body is strange and mysterious, and sometimes, not at all pleasant. A simple overproduction of chemicals can cause dark splotches on the skin that bleed pigmentation,along with aching joints and heart trouble--this is black bone disease, more formally known as alkaptonuria. In the whites of the eyes, black bone creates dark spots.

  1. Black Bone Eye Disease

    • Black bone disease is the buildup of homogentisic acid in the body, causing brown-black pigment to settle on bones and tissue--hence, its name. Dark pigmentation is visible in the whites of the eyes. Typically, eye function is not diminished.

    Rarity

    • Roughly one in 250,000 to 1 million people suffer from this disease worldwide. It is more common in Slovakia and the Dominican Republic. The mutation in the HDG gene is inherited in an autonomic recessive pattern, meaning both parents must have this gene mutation.

    HDG Gene

    • A defect of the HDG gene prevents the body from properly breaking down amino acids tyrosine and phenylalanine, causing the buildup of homogentisic acid in the skin and other body tissues. The acid leaves the body through urine, turning urine brownish-black.

    Effects

    • Pigmentation is visible in the whites of the eyes, or as blue-black speckles in the skin, sometimes staining clothes brown. Other symptoms of black bone disease include deposits of pigment causing cartilage to become brittle and fragment, which leads to arthritis (particularly of the spine and large joints). In the heart and blood vessels, pigment deposits cause aortic and mitrial valves to calcify or harden or formation of hard spots in the arteries. The pigment deposits can also form stones in the prostate.

    Treatment

    • Black bone eye disease is treated by treating the overlying disease. A low protein diet reduces amino acids phenylalanine and tyrosine, which lessens pigmentation in body tissue. High dose vitamin C decreases buildup of brown pigment. Other medical issues, such as arthritis and heart disease can be treated separately. There is no cure for black bone disease as of 2010, though research is ongoing.

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