Alkaptonuria
A genetic metabolic disorder due to deficiency of the enzyme homogentisic acid (HGA) dioxygenase. Deficiency of this enzyme leads to the three cardinal features of alkaptonuria (the presence of homogentisic acid in the urine), ochronosis (bluish-black pigmentation in connective tissue), and arthritis. Urine that turns dark is a characteristic feature.
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Alkyl group: In chemistry, a group of atoms derived from an alkane (a hydrocarbon with no carbon-to-carbon multiple bonds) by the loss of a hydrogen atom.
- Allelic
Allelic: Pertaining to an allele, an alternative form of a gene. A single allele is inherited from each parent.
- Allergen
Allergen: A substance that can cause an allergic reaction. Common allergens include ragweed pollen, animal dander, and mold.
- Allergic conjunctivitis
Inflammation of the whites of the eyes (conjunctivae), with itching, redness, and tearing, due to allergy.
- Allergic contact eczema
Also called allergic contact dermatitis, this is a red, itchy, weepy reaction where the skin has come into contact with a substance that the immune system recognizes as foreign, such as poison ivy or certain preservatives in creams and lotions.