* Skin: The pigment is deposited throughout the skin, but only becomes apparent in certain locations, where the concentration is great enough to be seen clinically. This usually occurs in areas where connective tissue is thick (joints, tympanic membrane) or close to the surface of the skin (thenar and hypothenar eminences and the sides of the fingers). In exogenous<unk> , the hyperpigmentation is localized to the area where the inciting agent is applied. Intradermal nevi can appear like blue nevi. * Eye: Ocular manifestations are frequent in patients with<unk> ; most commonly hyperpigmentation of the sclera, primarily observed symmetrically to both sides of the cornea within the palpebral fissure. Furthermore, brown pigment spots in the limbus are generally considered pathognomonic. These ocular signs generally occur early in the development of the disease and can serve as a valuable diagnostic feature of the disease. * Cartilage: Darkening and hardening of ear cartilage is a prominent feature of<unk> . Nasal cartilage is also frequently involved. The voice can be affected by hardening of the laryngeal cartilage. Stiffening of the ribs with decreased lung function has also been reported. The intervertebral cartilage is also more prone to herniation. * Connective tissue: Hardening of tendons and ligaments can predispose them to rupture. Color changes in the joints can be observed clinically. Arthropathy is common due to chronic inflammation and microruptures. * Heart valves: Stenosis can results from the increased rigidity of the connective tissue as well as chronic inflammation. Symptoms of exogenous<unk>  include: # Yellow-brown, banana-shaped fibers # Caviar-like papules # Brown-grey or blue-black hyperpigmentation Most of the lesions are seen on areas of the body that get the most sun.
Ochronosis
Zinc toxicity
Fluoride toxicity
Chromium toxicity
Copper toxicity
Lead poisoning
Skeletal fluorosis
Iron poisoning