View
231
Download
0
Category
Preview:
Citation preview
7/30/2019 Albinism m
1/14
Albinism
By
Dr Saad Al Mohizea
7/30/2019 Albinism m
2/14
OCA type 1
OCA type 1A complete absence of pigment in the skin, thehair, and the eyes
(OCA type 1B) moderate pigmentation in these tissues
(OCA type 1TS), ie, temperature sensitive). pigment in hairfollicles of the cooler areas of the body, such as the armsand the legs
All forms of OCA type 1 also present withphotophobia,moderate-to-severe reduced visual acuity, and nystagmus.
The latter two ocular dysfunctions result from a misroutingof the optic fibers from the retina to the visual cortex
7/30/2019 Albinism m
3/14
OCA type 2
does not present with complete absence ofpigment but rather manifests with a minimal-to-moderate amount of pigment remaining in
the skin, the hair, and the eyes. Many patients with OCA type 2 can develop
pigmented freckles, lentigines, and/or nevi
with age. The ocular presentations are similar to those
in OCA type 1
7/30/2019 Albinism m
4/14
OCA type 3
manifests with minimal pigment reduction in the
skin, the hair, and the eyes. This form of albinism
was previously referred to as Rufous albinism and
possibly Brown albinism. To date, OCA type 3 has only been genetically
confirmed in dark-skinned individuals (of African
heritage).
The ocular presentations are similar to those in
OCA type 1, but they are not as severe.
7/30/2019 Albinism m
5/14
other
OCA type 4 manifests with a phenotype
resembling OCA type 2
OA manifests with ocular depigmentation and iris
translucency. In addition, patients with OA presentwith congenital motor nystagmus that may be
accompanied by reduced visual acuity, refractive
errors, fundus hypopigmentation, lack of foveal
reflex, and strabismus. Cutaneous depigmentation
is not apparent
7/30/2019 Albinism m
6/14
mutations
OCA type 1 results from mutations in the tyrosinase gene, is inheritedas an autosomal recessive trait. The tyrosinase gene encodes anenzyme that initiates the synthesis of melanin using the substratetyrosine. Specifically, tyrosinase hydroxylates tyrosine todihydroxyphenylalanine (DOPA).
OCA type 2 results from mutation in the Pgene OCA type 3 results from mutation in the tyrosinase-related protein-1
(Tyrp1) gene, is inherited as an autosomal recessive trait.
OCA type 4 results from mutations in the membrane-associatedtransporter protein (MATP)
OA results from mutation in a gene on the X chromosome, is inherited
as an X-linked recessive trait. The function of the OA gene product isunknown
7/30/2019 Albinism m
7/14
DDX
Chediak-Higashi Syndrome (CHS); Hermansky-Pudlak Syndrome(HPS); and Griscelli Syndrome (GS).
HomocystinuriaMenkes Kinky Hair Disease
Phenylketonuria
Other Problems to be Considered:
HistidinemiaMenkes steely hair disease
Tietz syndromePrader-Willi syndromeAngelman syndrome
http://www.emedicine.com/derm/topic704.htmhttp://www.emedicine.com/derm/topic925.htmhttp://www.emedicine.com/derm/topic926.htmhttp://www.emedicine.com/DERM/topic708.htmhttp://www.emedicine.com/DERM/topic715.htmhttp://www.emedicine.com/DERM/topic712.htmhttp://www.emedicine.com/DERM/topic712.htmhttp://www.emedicine.com/DERM/topic715.htmhttp://www.emedicine.com/DERM/topic708.htmhttp://www.emedicine.com/derm/topic926.htmhttp://www.emedicine.com/derm/topic925.htmhttp://www.emedicine.com/derm/topic925.htmhttp://www.emedicine.com/derm/topic925.htmhttp://www.emedicine.com/derm/topic704.htmhttp://www.emedicine.com/derm/topic704.htmhttp://www.emedicine.com/derm/topic704.htm7/30/2019 Albinism m
8/14
DX
The hair bulb tyrosinase assay has been used to differentiatebetween OCA type 1 and the other forms of albinism. scalp hair bulbsare gently plucked from the patient and placed in a 0.1% solution of (L-DOPA) for to 4 hours. If the sample is from a patient with OCA type 1,the hair bulbs remain white. In contrast, samples from all other forms ofalbinism turn dark during the period.
For CHS, a confirmatory workup consists of analysis of a blood smearand the subsequent identification of neutrophils containing giantcytoplasmic granules.
For HPS, a confirmatory workup consists of electron microscopy ofplatelets and the subsequent identification of the absence of densebodies (delta granules) and bleeding time determination that
demonstrates a prolonged duration. For GS, confirmatory workup consist of immunological function
evaluation plus both CT and MRI for neurological abnormalities.
7/30/2019 Albinism m
9/14
RX
No treatment is available for
hypopigmentation in the skin, the hair, or the
eyes. The use of broad-spectrum
sunscreens and clothing is recommended to
prevent ultraviolet-induced damage to the
skin. Visual impairment can be improved by
using corrective lenses
7/30/2019 Albinism m
10/14
RX
No treatment is available for
hypopigmentation in the skin, the hair, or the
eyes. The use of broad-spectrum
sunscreens and clothing is recommended to
prevent ultraviolet-induced damage to the
skin. Visual impairment can be improved by
using corrective lenses
http://162.129.70.33/images/Oculocutaneous_Albinism_1_051003.jpg7/30/2019 Albinism m
11/14
http://162.129.70.33/images/Oculocutaneous_Albinism_1_051003.jpg7/30/2019 Albinism m
12/14
7/30/2019 Albinism m
13/14
7/30/2019 Albinism m
14/14
Recommended