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Vitiligo, likely meaning blemish, is a non-contagious skin condition that is defined by patches
of discoloration, or depigmentation.
Though vitiligo can affect any race or ethnicity, it tends to be most noticeable in people with
darker skin, like Canadian fashion model Winnie Harlow.
Vitiligo
Given the effect on a person’s appearance, pigment loss can really impact a person’s
quality of life.
The skin is divided into three layers--the epidermis, dermis, and hypodermis.
The hypodermis is made of fat and connective tissue that anchors the skin to the underlying
muscle.
Just above is the dermis, which contains hair follicles, nerves and blood vessels.
And just above, the outermost layer of skin, is the epidermis.
The epidermis itself has multiple cell layers that are mostly keratinocytes -
Vitiligo
which are
named for the keratin protein that they’re filled with.
Keratin is a strong, fibrous protein that allows keratinocytes to protect themselves
from getting destroyed when you rub your hands through the sand at the beach.
Keratinocytes start their life at the deepest layer of the epidermis called the stratum
basale, or basal layer, which is made of a single layer of small, cuboidal to low columnar
stem cells that continually divide and produce new keratinocytes that continue to mature
as they migrate up through the epidermal layers.
But the stratum basale also contains another group of cells - melanocytes, which secrete
a protein pigment, or coloring substance, called melanin.
Melanin is actually a broad term that constitutes several types of melanin found in people of
differing skin color.
These subtypes of melanin range in color from black to reddish yellow and their relative
quantity and rate at which they are metabolized define a person’s skin color.
When keratinocytes are exposed to the sun, they send a chemical signal to the melanocytes,
which stimulates the melanocytes into making more melanin.
The melanocytes move the melanin into small sacs called melanosomes, and these get taken
up by newly formed keratinocytes, which will later metabolize the melanin as they
migrate
into higher layers of the epidermis.
Melanin then acts as a natural sunscreen, because its protein structure dissipates,
or scatters, UVB light--which if left unchecked can damage the DNA in the skin cells and lead
to skin cancer.
Melanocytes can also be found in the dermis, at the base of the hair follicle, and in the
eye where they help color hair and the iris.
In vitiligo, there’s a loss of melanocytes or an absence of their function.
Histologically, having less melanin in the epidermis
results in white depigmented patches.
These patches are classified by type.
There’s non-segmental vitiligo which is the more common type that affects any age
group, and it occurs at various locations that are mirrored on both sides of the body.
There’s also segmental vitiligo which mostly affects children, and occurs in segments along
a single spinal nerve typically on only one side of the body without crossing the midline.
The exact cause of melanocyte destruction isn’t known, but it does seem to be linked
to both genetic and environmental triggers.
In non-segmental vitiligo, there seems to be an autoimmune element - where immune cells
attack the melanocytes.
In segmental vitiligo,
there seem to be neural factors, where nerves release neurochemicals
that damage the melanocytes.
Other causes may be that the melanocytes get damaged by a buildup of toxic metabolites
as they make melanin or in other metabolic pathways.
One interesting observation is called the Koebner phenomenon, and it’s when vitiligo
develops in skin soon after there has been a trauma, like a cut, abrasion, or burn.
The main symptom of vitiligo is the irregular, round or oval shaped patches of depigmentation
appearing within normally pigmented skin.
The patches can range in size from
millimeters to centimeters and can sometimes expand and
merge with other patches over time.
The body hair and the iris may also be depigmented in affected areas.
Non-segmental vitiligo tends to affect the hands, forearms, neck, scalp, feet, and face;
while segmental vitiligo, tends to affect areas of skin near dorsal roots from the spinal
cord, particular in the face following the trigeminal nerve.
The diagnosis of vitiligo is based on the appearance of depigmented patches, but a skin
biopsy can also be done.
There are two main treatments.
When the affected area is small, cosmetic cover up and topical immune-suppressants can
be applied directly to skin.
When the affected area is large, systemic
immune-suppressants, UV phototherapy, skin-bleaching,
and in severe cases, skin grafts, can all be tried.
Whatever the course of therapy, sunscreen is recommended to prevent darkening of the
skin areas immediately surrounding and contrasting the depigmentation areas, and to reduce the
risk of skin cancer.
So, to recap: Vitiligo is a non-contagious condition where destruction of melanocytes
and loss of melanin production leads to areas of depigmentation on the skin.
Non-segmental vitiligo tends to affect the hands, forearms, neck, scalp, feet, and face;
while segmental vitiligo tends to affect areas
of skin near dorsal roots from the spinal
cord, particularly in the face following the trigeminal nerve.
For small areas, cosmetic cover up and topical immune-suppressants can be used.
For large areas, systemic immune-suppressants, UV phototherapy, skin-bleaching, and even
skin grafts, can be used.
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