Melasma and ochronosis are two different types of skin conditions, both causing discolouration in the skin. However, the similarities between the two disorders do not extend much further beyond colouration. Although melasma and ochronosis can be classified as hereditary, melasma is known to be caused by several other factors as well.
While ochronosis is diagnosed as a result of a defect in the HGD gene (or the homogentisate 1,2-dioxygenase gene, responsible for providing instructions on the creation of an enzyme called homogentisate oxidase, a substance active primarily in the liver and kidneys), the cause of melasma is less specific. While melasma occurs more frequently in those with a family history of the disorder, the skin condition occurs primarily in pregnant women and women taking contraceptives or other hormonal remedies. Sun exposure, reactions to odorised bath products and ethnicities of darker skin tones are all factors as well. Ochronosis is the collection of symptoms caused by alkaptonuria, a genetic condition in which the body is unable to break down the amino acids tyrosine and phenylalanine. As a result, homogenistic acid builds up inside skin tissue (due to the defect in the homogentisate oxidase enzyme) while excess is evacuated through the urine.
With melasma, brown to grey patches form primarily on the face (although occurrences can result on the arms as well). With ochronosis, skin discolouration ranges from blue to black and occurs predominantly around the ears. While skin discolouration is specific to melasma, additional symptoms accompany ochronosis. Eyes may become discoloured as well and arthritis can worsen (bones become discoloured as well as the acid enters the tissue).
Melasma can disappear on its own, especially with women at the termination of pregnancy or the cessation of contraceptives or hormonal treatments. If melasma does not desist, a number of treatments are available. These treatments include skin creams, chemical peels, laser treatments, sun protection or other prescribed medications. Ochronosis is more difficult to treat as alkaptonuria is a life-long, incurable disease. Although both parents must have the HGD defect in order to pass it on to newborns, those diagnosed with alkaptonuria (ochronosis) have several treatment options, especially if discovered earlier on in life. A low-protein diet reduces the intake of amino acids and thus reduces the amount of homogenistic acid that is produced. Vitamin C has also been found to slow the build-up of the acid inside the body. A regulated diet earlier on in life can reduce the frequency of complications later on. Complications can range from arthritis or kidney stones to heart or coronary artery disease.