Albinism Presentation contents: 1- Introduction 2- Epidemiology 3- Biochemical bases 4- Management and Treatment

1. Prepared by:
epa ed by
Yasser Sh. Barhoum
Mohammed Bakeer
Supe sed by
Supervised by:
Prof. Abed Nasser Abu shahla
Master Program of Biological Sciences, Al‐Azhar University‐Gaza (December, 2013)

2. INTRODUCTION

3. ALBINISM
A
S
Definition:
D fi iti
•Is a congenital disorder characterized by
the complete or partial absence of
pg
,
melanin pigment in the skin, hair and
eyes.
•D t b
Due to absence or defect of tyrosinase
d f t ft
i
enzyme involved in the production of
melanin.

4. History
i
A man in the 17th century named
A
i th 17th
t
d
Balthazar Telez, who was an explorer,
came up with the name "Albino", which
g ,
means white negro, after he saw an
albino African tribe. Balthazar thought he
was seeing two different races of people.
was seeing two different races of people
This was the first discovery of albinism.

5. Albinism also called Hypo‐pigmentation,
achromia, achromasia, or achromatosis
ALBINO:
organism with complete absence of melanin.
ALBINOID or ALBINIC:
an organism with only a diminished amount
an organism with only a diminished amount
of melanin.

6. Melanin
i
• Al
Also called pigment, melanin is a substance
ll d i
t
l i i
bt
that gives the skin and hair its natural color.
• It also gives color to the iris of the eye,
feathers, and scales.
eat e s, a d sca es
• Melanin is synthesized from the amino acid
tyrosine.
t
i
• In the skin, melanin is formed by cells
,
y
called melanocytes.

7. There are three basic types of melanin:
There are three basic types of melanin
1. Eumelanin: have black and brown color.
2. Pheomelanin: have red or yellow color,
responsible for red hair and freckles.
responsible for red hair and freckles
3. Neuromelanin: is found in the brain,
though its function remains obscure.
Both pheomelanin and eumelanin are found in human
skin and hair, but eumelanin is the most abundant
melanin in humans, as well as the form most likely to be
l i i h
ll th f
t lik l t b
deficient in albinism.

8. Melanin have some benefits
1. Melanin provides a natural protection
against the harmful effects of ultraviolet
against the harmful effects of ultraviolet
rays of the sun.
2. Melanin is also a mechanism for
absorbing heat from the sun.
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3. Melanin, also important for sharpness of
vision.
ii

9. Types of A i i
f Albinism
1) Oculocutaneous Albinism (OCA)
1) Oculocutaneous Albinism (OCA)
‐ Affecting the eyes, skin and hair.
‐ People with this type of albinism have white or
pink hair, skin, and iris color, as well as vision problems.
‐ Most severe type.
‐H
Have 4 types (1,2,3,4)
4t
(1 2 3 4)
2) Ocular Albinism (OA)
‐ Aff ti th
Affecting the eyes only.
l
‐ Skin color is usually normal or slightly lighter than the
skin of other family members.
skin of other family members.
‐ Eye color may be in the normal range but there is no
pigment in the retina.
‐ Have 3 types.

10. Genetics of Albinism
G
i
fA i i
Most types of albinism are inherited as an
Most types of albinism are inherited as an
Autosomal recessive but some types are X‐
linked Recessive.
linked Recessive
1) Autosomal Recessive:
• Most types of albinism are inherited when an
individual receives the albinism gene from both
parents.
• If parents are carriers, the child has a 25% chance
of being completely normal, a 50% chance of being
fb i
l l
l 50% h
fb i
a carrier, and a 25% chance of getting albinism.

12. 2) X‐linked Recessive:
The exception: some types of ocular albinism, which is
The exception: some types of ocular albinism which is
passed from mothers to their sons.

13. What if one gene is
normal and one gene
p
does not produce the
enzyme?
The one functioning gene produces enough
enzyme to make melanin for normal coloration

14. EPIDEMIOLOGY

15. Causes
C
• Albi i i
Albinism is caused by mutation or an
db
t ti
alteration of the gene that makes the
melanin pigment.
l i i
• Albinism is inherited genetically as
previously stated, it is autosomal recessive
previously stated it is autosomal recessive
and some types x‐linked recessive
inheritance.
inheritance

16. Prevalence and Incidence
P
l
d I id
• The international average for albinism is about
The international average for albinism is about
1 in 20,000.
• I th U S 1
In the U.S., 1 person in 17,000 has some type
i 17 000 h
t
of albinism.
• Research indicates that the first type,
Oculocutaneous Albinism (OCA) happen by 1
per 40,000 of the population.
While the second type, Ocular Albinism (OA)
• While the second type, Ocular Albinism (OA)
happen by 1 per 15,000 of the population.

17. Prevalence and Incidence
P
l
d I id
• H
Happens all over the world.
ll
th
ld
• Affects all vertebrates
Affects all vertebrates.
• Affects people from all races.
p p
• Effects men and women of all ages.
• Albinism has been observed in many animals
also.

18. Symptoms
Skin and Hair
ki
d i
Pale skin or
Pale skin or
patchy skin
White hair
White hair
Eyes
Usually pale blue or light
Usually pale blue or light
brown, but can
sometimes appear pink‐
red
Extremely poor vision
Light sensitivity
(Photophobia)
Rapid eye movements
(Nystagmus)
Strabismus
b

21. Absence of normal pigments in eyes resulting in
Ab
f
l i
t i
lti i
pale blue, light brown or red eyes
This is not because the iris is red, but
because there is so little color that the
blood vessels show through the iris.

22. Albinism in animals

23. Prognosis
i
• Growth development and intellectual
Growth, development and intellectual
development in the albino child are normal.
• Vision is invariably severely impaired.
• Albinism does not affect the expected
lifespan.
• People with albinism may be limited in their
activities because they can't tolerate the
because they can't tolerate the
sun.

24. Complications
C
i i
• Lack of skin pigmentation making more
Lack of skin pigmentation making more
susceptible to sunburn and skin cancer.
• Blindness.
• Albinism may cause social problems,
because people with albinism look different
b
l
h lb
l k d ff
from their families, peers and other
members of their ethnic group.

25. BIOCHEMICAL
BASIS

26. Biochemical Bases
i
i
• Albi i i
Albinism is caused by a genetic lack of
db
ti l k f
melanin.
• Melanin is synthesized from the amino
Melanin is synthesized from the amino
acid tyrosine.
• Tyrosinase breaks down tyrosine.

27. Biosynthetic pathways
i
i
•
The first step of the biosynthetic pathway for both eumelanins and pheomelanins is
catalyzed by tyrosinase:
Tyrosine → DOPA → dopaquinone
•
Dopaquinone can combine with cysteine by two pathways to form pheomelanins:
Dopaquinone + cysteine → 5‐S‐cysteinyldopa → pheomelanin
Dopaquinone + cysteine → 2‐S‐cysteinyldopa → pheomelanin
•
Also, Dopaquinone can be converted to leucodopachrome and follow two pathways
to form the eumelanins:
f
h
l i
Dopaquinone → leucodopachrome → dopachrome → 5,6‐dihydroxyindole‐2‐carboxylic acid (DHICA)
→ quinone → eumelanin
Dopaquinone → leucodopachrome → dopachrome → 5,6‐dihydroxyindole (DHI)→ quinone →
eumelanin

29. Albinism: mutation in tyrosinase, the first enzyme in the pathway that
converts tyrosine to melanin

30. The result of no melanin is
an albino.

31. Interestingly, individuals with phenylketonuria can have light skin and hair at birth,
because of low levels of tyrosine.
However, phenylketonuriacs are not albinos, because they obtain sufficient
amounts of tyrosine in their diets to support melanin biosynthesis.

32. DIAGNOSIS

33. Diagnosis
i
i
• Albinism can first appear at birth because it is a
Albinism can first appear at birth because it is a
physical deformity that never changes.
Detected at birth because of irregular pigmentation.
• Detected at birth because of irregular pigmentation.
• Diagnosis is based on careful history of pigment
development and an examination of the skin, hair
p
,
and eyes.
• The most accurate way to determine albinism is
The most accurate way to determine albinism is
genetic test, for example : Chorionic Villus Sampling
Test(CVS) and Amniocentesis can identify albinism
and Amniocentesis can identify albinism
during the second trimester of pregnancy.

34. Diagnosis
i
i
• Hair from the scalp can be used to assess tyrosinase
Hair from the scalp can be used to assess tyrosinase
activity by determination the DOPA and melanin
concentration.
• DOPA and melanin assessed by a radioactive biochemical
assay, in which the samples are incubated with a
radiolabelled tyrosine precursor and the amount of
radiolabel released after enzymatic conversion quantified
spectrophotometrically.
spectrophotometrically
• The value of this test is debatable since a negative result
indicates OCA1 but a positive result still leaves the
i di t OCA1 b t positi e res lt till l
th
possibility of OCA1, OCA2, OCA3, or OA1.

35. MANEGMENT
MANEGMENT
and
and
TREATMENT

36. MANEGMENT and TREATMENT
• There is no cure for albinism because albinism is a genetic
There is no cure for albinism, because albinism is a genetic
disorder, treatment is limited.
• Treatments only reduce the symptoms.
• The skin and eyes must be protected from the sun.
Skin
Ski
• The skin can be protected by using sunscreen creams .
• Always wear special UV protective clothing to reduce
sunburn risk.
• Children should receive annual skin assessments to screen
for skin cancer or lesions that could lead to cancer.

37. MANEGMENT and TREATMENT
Eyes
• Many children will need to wear prescription Glasses or
y
p
p
lenses, which can provide improvements in their vision.
• Wear dark Sunglasses (UV protected) may relieve
photophobia.
• Eye muscle surgery is sometimes recommended to correct
abnormal eye movements (Nystagmus).
abnormal eye movements (Nystagmus)
• For strabismus, ophthalmologists prefer to treat infants
starting at about six months of age, before the function of
g
g ,
their eyes has developed fully.
• Children should receive annual examinations by an
ophthalmologist.
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