Showing posts with label color. Show all posts
Showing posts with label color. Show all posts

Wednesday, December 15

Yellow skin discoloration - Causes of yellow skin color

Skin discoloration - Yellow skin color
There are many causes for yellow skin color and discoloration and the condition has to be evaluated immediately as some are harmless changes, whereas some are due to serious disorders which can be life threatening, requiring immediate treatment.

Causes of yellow skin color

Certain pigments in the food like carotene get deposited in the epidermal layers when in excess and their presence causes yellow skin color change which is harmless. However, certain disorders of the body systems can interfere with the metabolism of carotene.

These disorders induce carotene deposition and discoloration even though serum levels of carotene are normal, requiring investigation. The excretion of certain medicines through epidermal layers shows up as yellow skin color. The buildup of bilirubin in the blood and the onset of jaundice is due to many diseases and disorders leading to yellow coloration.

Jaundice caused yellow skin discoloration

Jaundice (aka icterus) is yellow pigmentation of the dermal and epidermal layers, sclerae (white of eyes) and mucous membranes. The increased levels of bilirubin in blood plasma (1.5 mg/dL), also known as hyperbilirubinemia, causes jaundice. Hyperbilirubinemia can be due to various factors and categorized into pre-hepatic, hepatocellular and post-hepatic types.

Any of the causes of increased rate of breakdown of red blood cells (hemolysis) leads to pre-hepatic jaundice. Tropical diseases like malaria, genetic diseases like thalassemia, organ disorders like hemolytic uremic syndrome affecting kidney, bilirubin metabolism disorders and high fevers as in leptospirosis (rat fever) causes jaundice and dermal color change.

In hepatocellular jaundice there is usually cholestasis (bile not flowing to duodenum) and the causes are hepatitis of any origin, liver toxicity, genetic disorders like Gilbert's syndrome, alcoholic liver disease and Crigler-Najjar syndrome. Post-hepatic jaundice is usually due to interruption to the flow of bile inside liver as well as to duodenum.

The causes can be gallstones in the bile duct, cancer of pancreas, obstruction by liver flukes, biliary atresia (passage closed or absent), ductal carcinoma (tumor in the duct), pancreatitis (inflammation of the pancreas) and pancreatic pseudocysts (circumscribed collection of fluid rich in pancreatic enzymes, blood, and necrotic tissue). Jaundice discoloration conditions require a combination of liver function tests to arrive at the exact causes and diagnosis.

Newborn and yellow skin color

Mild jaundice is observed in many newborns and this neonatal jaundice is usually harmless. This condition may be seen from second day to eighth day in normal birth and for about two weeks in premature births. It is presumed that apart from higher turnover of red blood cells, physiological and metabolic adjustments after birth, causes this increase in serum bilirubin in newborn.

This increased levels of bilirubin gets lowered with regular urination and bowel movement; hence regular and proper feeding of the baby are very important. However in a few rare cases, neonatal hyperbilirubinemia causes kernicterus, a brain-damaging condition, resulting in lifelong disability.

To avoid this risk it is better to treat the neonatal jaundice by exposing the baby to intense photo-therapy. Inadequate feed, infections, internal bleeding or liver disorder or malfunction or incompatible Rh blood factors of mother and child can also lead to skin discoloration requiring proper treatment.

Primary carotenoderma

Ingesting food containing high levels of carotenoids leads increased serum levels of carotene and its deposit in the skin. Carotenoids are deposited in the intercellular lipid containing spaces in stratum corneum.

Thick epidermal layers and regions of increased sweating like nasolabial folds, palms, knees and soles bear increased deposits and show greater color change. Carotenoderma differs from yellow color due to bilirubin in not showing coloration of white of eyes. Primary carotenoderma yellow color usually disappears after the reduction in intake of carotenoids.

Secondary carotenoderma

Usually a underlying disease condition causes increase in serum levels of carotene and secondary carotenoderma discoloration, though the carotene intake is normal. Kidney malfunction or dysfunction is usually associated with decreased excretion of carotenoids and hypercarotenemia and color change.

Impaired conversion of carotenoids to retinol is seen in diabetes mellitus and hypothyroidism. The associated increase in serum lipids as seen in diabetes mellitus, nephrotic syndrome and hypothyroidism causes yellow skin color and secondary carotenoderma. In Anorexia nervosa, a self-imposed starvation, diets may be rich in carotene. Liver disease also leads to yellow color change due to poor utilization and breakdown of carotene resulting in its increased serum levels.

Yellow skin color due to medicines

The use of certain medicines in the treatment of diseases causes yellow coloration. Tyrosine kinase inhibitors (TKIs) are used in the treatment of various cancers. Sunitinib (a TKI) used in the cancer therapy is associated with many adverse events and yellow color changes of the epidermal layers. Color changes start after a week of treatment and with the continuation of the treatment, color intensification has been noticed.

The sclerae and mucous membranes are spared of the color change and on the discontinuation of medicine resolves the coloration. Probably the excretion of the chemical via the epidermis causes this coloration. Another TKI, sorafenib also causes a diffuse yellow discoloration of the skin.

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Friday, August 14

Human skin color changes - Skin color variations

Changes and variations in human skin color
The diversity in the human skin color is the cumulative result of genetic adaptations brought about by the evolutionary processes of natural selection acting on the genetic variability of the population.

Human skin color change is determined by six genes and their several alleles. There is a big mix of combinations and a great variety in the skin tone is produced. The geographical distribution and evolutionary natural selection have influenced the genetic adaptations and random changes.

Changes in the normal skin color are due to certain biological, environmental or pathological conditions. Color changes are mostly temporary and are produced by the tanning, diseases and chemicals. Extraneous factors like the amount of β-carotene present in the epidermal and subcutaneous tissues and the level of oxygen saturation in the hemoglobin protein in the dermis also causes changes of the normal human skin color temporarily.

Melanin in skin pigment

Human skin color, tone and complexion are basically determined by the amount and types of melanin pigment present in the epidermal layer. The concentration and kind of melanin pigment contributing to human complexion is determined by the genotype (genetic makeup) of an individual.

Melanin is present in three forms namely pheomelanin, eumelanin and neuromelanin. Pheomelanin pigment imparts color changes ranging from red to yellow. Eumelanin imparts brown, dark brown and black color. The third type of melanin, neuromelanin, is present in the brain. All human beings have melanin pigment in their skin. Individuals with lighter complexion produce pheomelanin and people with dark complexion mostly produce eumelanin.

People with dark complexions may have slightly higher concentration of melanin producing cells (melanocytes). However human skin color changes are affected more by the quantity, type, size and pattern of distribution of the pigment than the melanocytes number. The color changes may be dark-black-brown when the skin pigmentation is very high. In the case of very little pigment in the epidermis, there is no coloration and the blood in the underlying blood vessels may impart a pink color. There is a varied range of complexion between these two extremes depending upon the type and quantity of melanin in the human epidermis.

Melanin pigment protects the epidermal layers and dermis from ultraviolet rays of sun which can cause skin cancer. Light colored individuals have tenfold risk of getting cancer under similar sunlight exposure when compared to individuals with darker complexion.

Melanin preserves folic acid from getting destroyed due to ultraviolet-A rays. Folic acid is very essential for fetal brain development and brain function in humans. Vitamin D is synthesized in the skin with the help of sunlight. As melanin blocks the sunlight from reaching deeper layers, it can cause vitamin D deficiency in dark-colored people, especially in higher latitudes.

Human skin color changes


Human skin complexion types

Knowing your complexion is very important in order to save yourself from skin cancer, vitamin D deficiency and also for choosing the right type of sunscreen. Thomas B. Fitzpatrick from Department of Dermatology of Harvard Medical School, developed a numerical skin typing which is now known as Fitzpatrick phototyping scale.The updated version of Fitzpatrick scale classifies the changes in the complexion into six types.
Type I
  • white or pale white, very fair
  • Type II
  • white, fair
  • Type III
  • white to olive
  • Type IV
  • moderate brown
  • Type V
  • brown
  • Type VI
  • very dark brown, black
  • People with complexion type I, II or III are prone to sunburn and have greater risk of skin cancer. People with types IV, V and VI may become deficient in vitamin D in higher latitudes.

    Evolution of changes skin color in humans

    human skin color changes
    Human skin color changes
    The common human ancestor lived in sub-Saharan Africa. They lived in regions of intense sunlight and ultraviolet radiation. The evolutionary changes of cooling mechanisms like loss of the body hair and increased efficient perspiration helped them in adapting to the environment. Early humans had dark skin pigment and fairer complexions have evolved later as genetic adaptations.

    The development of dark pigment was an adaptation for preserving folate and DNA from destruction and damage by ultraviolet radiation. The presence of high amount of melanin pigment protected them from the ill-effects of sun exposure. Change in human skin color is an example of natural selection influenced by the human migration and connected socio-geographic factors. These changes were influenced by human migration to colder geographic zones. Earlier most of the people with darker pigmentation lived within 20º of the equator and people with lighter pigmentation lived outside the 20º latitude.

    The mass migrations of people in the past five centuries has upset the evolution of epidermal pigment in humans and has brought in many changes and related problems. A certain amount of ultraviolet radiation is necessary for the dermis to produce vitamin D. People with darker skin pigment living in higher latitudes are at the risk of vitamin D deficiency, as the high concentration of melanin acts as a shield cutting off ultraviolet rays. Similarly, people with lighter skin pigmentation living in the tropical regions are in the constant risk of sunburns and cancer.

    Genetics of human skin complexions

    Complexion and color are polygenic traits. Human complexion is the result of the complex combination of a number of genes and changes in their alleles. The MC1R (melanocortin 1 receptor) gene and its changes are responsible for the type of melanin to be produced by the body. The KIT ligand (KITLG) gene and its mutant alle A326G (rs642742) gene are involved in the permanent survival, proliferation and migration of melanin producing cells.

    Agouti gene is involved in the production of agouti signalling peptide (ASIP) which acts as an inverse agonist causing changes in melanocytes to synthesize the pheomelanin instead of the eumelanin. Solute carrier family 24 member 5 (SLC24A5) gene, solute carrier family 45 member 2 (SLC45A2 or MATP) gene, TYR gene and Ser192Tyr (rs1042602) gene are some of the genes involved in the final determination of human skin color.

    Image source: http://en.wikipedia.org/wiki/File:Coloured-family.jpg
    Author: Henry M. Trotter | license: public domain
    Current topic: Changes and variations in human skin color.

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