Melanin Synthesis, Albinism and Vitiligo for Medical Student

1. Rajendra Dev Bhatt
Asst.Professor /Clinical Biochemist

2. MELANIN
• Skin color is determined by the relative
concentrations of black & red melanins
• This is dependent on genetic and environmental
factors
• Moles: due to hyperpigmentation caused by the
hyperactivity of melanocytes
• White patches: due to localized absence or
degeneration of melanocytes from the skin.

3. MELANIN SYNTHESIS
• Melanin is black pigment of skin, hair & eyes
• Synthesis occurs in melanosomes present in
melanocytes.
• Tyrosine is the precursor of melanin and tyrosinase
is the enzyme involved in it’s formation
• Melanochromes formed from tyrosine polymerizes
to form melanin polymers

5. MELANIN TYPES
Eumelanin ( brown & black),
Pheomelanin, and
Neuromelanin
Tyrosinase is a copper-containing enzyme that is
present in melanocytes

6. MELANIN TYPES
Eumelanin:
black eumelanin in the absence of other pigments causes grey
hair.
brown eumelanin in the absence of other pigments causes yellow
(blond) color hair.
Pheomelanin:
imparts a pink to red hue, depending upon its concentration.
concentrated in the lips, nipples, glans penis, and vagina.
When small amount of brown eumelanin in hair mixed with red
pheomelanin, the result is red hair.
Neuromelanin:
dark polymer pigment produced in specific populations of
catecholaminergic neurons in the brain

7. Tyrosine
DOPA
Dopaquinone
Leucodopachrome Cysteine
5,6-Dihydroxyindole Melanin red polymers
Indole 5-6-quinone
melanochrome Melanin black polymers
Tyrosine hydroxylase
Tyrosinase
Tyrosinase

8. Metabolism of Tyrosine
Phenylalanine
hydroxylase
MELANIN
DOPAMINE
NOREPINEPHRINE
EPINEPHRINE
THYROXINE
P
H
E
NY
L
AL
A
NI
N
E
T
Y
R
O
S
I
N
E

9. PHENYLACETATE
PHENYLLACTATE
Melanin
Phenylalanine
(-)Phenylalanine hydroxylase
Phenylketonuria
Tyrosine
Homogentisate
Maleylacetoacetate
Different
products
like Dopa,
Dopamine,
Thyroxine
etc.
Albinism
Alkaptonuria
(-)Tyrosinase

10. ALBINISM

11. HISTORY
Balthazar Telez coined the term “albino”,
meaning white Negro, when he saw white
African tribe members along the coast of
West Africa. He and the other explorers
thought they were seeing two different races
of people

13. WHAT IS ALBINISM?
• Albinism is a group of genetic conditions that
causes a lack of pigment- melanin.
• It can effect only the eyes or both the eyes and
skin.
• Most types of albinism are inherited when an
individual receives the albinism gene from both
parents.
• The exception is one type of ocular albinism,
which is passed on from mothers to their sons.

14. DESCRIPTION
• Inherited by one of several modes:
• autosomal recessive, autosomal dominant, or Complete albinism
• Affected people may appear to have white hair, skin & iris color.
• They may have vision defects and photophobia.
• Oculocutaneous albinism is most severe form resulting from a deficiency of
tyrosinase activity, causing a total absence of pigment from the hair, eyes &
skin

15. DEFECTS
Tyrosinase enzyme deficiency or reduced activity
 Mutation in Tyrosinase related protein (TRP-1) gene
 Recessive inheritance of OCA1 and OCA2

16. SYMPTOMS
• Absence of pigment from the hair, skin, or
iris of eyes
• Lighter than normal skin and hair or
complete albinism
• Most forms of complete albinism have some
of the following possible symptoms:
• Rapid eye movements
• Strabismus (eyes not tracking properly)
• Photophobia (avoidance of light because of discomfort)
• Decreased visual acuity
• Functional blindness

17. ALTERNATE NAMES
Hypopigmentation
Ocular Albinism
Oculocutaneous Albinism

18. TREATMENT
The skin and eyes must be protected from the sun. Sunglasses (UV
protected) may relieve photophobia.

19. PROGNOSIS
Albinism does not affect the expected
lifespan.
Activities may be limited by intolerance to
the sun.

20. VITILIGO
Vitiligo is a disease in which the pigment cells of the skin, melanocytes, are
destroyed in certain areas.
Symptoms and signs of vitiligo include loss of skin color in the form of
depigmented, or white, patches of skin in any location on the body.
Vitiligo can be focal and localized to one area, or it may affect several different
areas on the body.
The exact cause of vitiligo is unknown, although most experts believe that it is
an autoimmune condition in which the body's immune system mistakenly
attacks and destroys certain cells within the body.

21. VITILIGO
Most people who have vitiligo will develop the condition prior to age 40; about
half develop it before age 20
Vitiligo is sometimes associated with other medical conditions, including thyroid
dysfunction.
There is no way to determine if vitiligo will spread or remain confined to one
location.

22. MELANOTIC MACULE
The melanotic macule in the
mouth equivalent of a freckle
or brown pigmented patch of
the skin.
One-third of lesions occur on
the vermilion border of the
lower lip, along with the
buccal mucosa, gingiva and
palate.
One of every 1,000 adults

23. CAUSES OF MELANOTIC MACULE
Children: racial origin, no treatment required.
Adults: may be smoke-induced, drug-induced, hormone-induced or
spontaneous (without cause), and
 Biopsied to rule out malignant melanoma.
 Some inherited diseases show brown pigmentation of the oral membranes.