Skin darkening is a skin disease secondary to hyperpigmentation. It is either local or generalized. Melanin pigment is present in normal skin in different concentration. Melanin pigmentation is in higher concentration in darker skin and lower concentration in lighter color skin. Melanin pigment prevents harmful effects to skin from ultraviolet light of sunlight. Melanin pigment is produced by melanocytes located in layer of skin called epidermis. In a normal skin a patch hyperpigmentation of skin is noticeable. It is a disease and mostly benign exposure to sun for prolonged period causes generalized darkening of skin following over activities of melanocyte to secrete melanin pigment to protect skin from harmful effect of ultraviolet lights. Energy from ultraviolet light is absorbed by melanin pigments thus protecting skin from over exposure to light.
Skin may become darker after injury from blood collection under skin. Patient often suggests history of trauma or bleeding. Skin color changes to normal color after few days. Generalized or widespread hyperpigmentation may be seen after pregnancy or taking birth control pills.
Causes of Darken Skin or Hyperpigmentation
Localized Causes of Darken Skin or Hyperpigmentation
Painful Localized Darken Skin
- Bruises: skin laceration, edema of subcutaneous tissue and bleeding is seen on examination.
- Hematoma: subcutaneous soft tissue swelling because of subcutaneous or muscular blood clot.
- Fracture: bones or dislocated joint is discolored because of subcutaneous bleeding and swelling from blood clot. Joint of area of trauma is extremely painful.
Painless Localized Darken Skin
- Darkened skin around joints.
- History of dermatomyositis, an inflammatory skin disease.
- Abnormal pigmentation of skin over knuckle, knee, ankle or elbow joints.
- Joints appear abnormally dark and red,Patches of depigmentation among patches of hyperpigmentation.
- Later stage form small ulcers on the skin that can appear red or black.
- Skin lesion with rash and thick keratinization of epidermis.
- Severe itching and occasional bleeding. Skin surrounding psoriatic rash is hyperpigmented.
- Darkened skin around joints.
- Scarring of the skin and joints.
- Associated with systemic disease involving kidney, lungs and liver.
- Joint discoloration.
- Skin: dark patches and growth of dark skin layers are seen.
- Lesion is common over folds of skin, such as your armpit, inside of your elbow, back of your knee or the back of your neck.
- May be isolated involving skin over knuckles.
- Insulin resistant hyperpigmentation – the excess insulin interacts with your skin cells, leading to patches of excessive skin growth and hyperpigmentation.
Generalized: Melanin cell overgrowth.
- Birth control pills.
- Excessive exposure to sun.
- Hyperthyroidism (overactive thyroid).
Congenital or Genetic Conditions Including:
- Neurofibromatosis (café au lait macules): disease involves hypertrophy of nerve endings. Generalized light or dark brown patches are spread over skin, present from birth.
- Xeroderma pigmentosum.
- Freckles are generalized and spread as tiny small dark moles across the skin.
- Diabetic Neuropathy: Diabetic hyperpigmentation are light brown, scaly patches due to diabetes-related changes in blood vessels.
- Addison’s Disease: is a disease of adrenal cortex. Inadequate formation of cortisone hormone causes pituitary to secret more of corticotropin hormone. Corticotropin is elevated in Addison’s disease. Corticotropin also stimulated melanocytes. Increase activities of melanocyte causes increase secretion of melanin pigments resulting in darker skin.
- Lupus: is an autoimmune disease. Multiple organ as well as skin is affected by lupus. Butterfly shape skin rash gets darker with time and produces darker hyperpigmented skin, which is often wide spread over the trunk and arms.
- Alkaptonuria: is a genetic disease unable to metabolize certain amino acids. Acidic precursor of amino acids accumulates under skin and joint causing skin discoloration and joint pain. Skin exposed to sunlight (ultraviolet light effect) becomes darker and widespread hyperpigmented skin become predominant sign.
- Melasma: is hyperpigmentation of skin over face, forehead and chin. More common in female taking birth control pills. Also seen during pregnancy and skin discoloration may disappear or lessen after delivery.
- Sun Damage: or over exposure to sun causes hyperpigmentation of skin expose to sun.
Symptoms of Darken Skin or Hyperpigmentation
- Blood examination
- Skin biopsy
Treatment for Darken Skin or Hyperpigmentation
- Exercise: insulin resistance hyperpigmentation may respond to daily exercise.
- Medication: corticosteroids.
- Skin darkening cream.
- Sunscreen lotion.
Consult a dermatologist, sooner the better. Endocrinal disorder can be reversible if diagnosed earlier and treated sooner.
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