Albinism Flashcards
What is albinism?
represents a heterogenous group of inherited pigmentary disorders
- characterised by generalised reduction of ocular, cutaneous and hair pigmentation from birth.
Types of albinism?
4 types of Oculocutaneous albinism (OCA 1-4)
Describe OCA 1?
OCA 1A - total absence of tyrosinase enzyme
> total lack of melanin production
OCA 1B - low level or very defective tyrosinase (<5-10% of normal)
> greatly diminished melanin production
OCA 2?
mutation of p-gene
> Lack of essential acidic environment in melanosomes for melanogenesis.
OCA 3?
mutation of tyrosinase associated protein 1 gene
> loss of factor that stabilizes tyrosinase in melanosomes
OCA 4?
mutation of membrane associated transporter protein
> dysfunctional melanosomal membrane
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Desvribe OCA 1?
results from total absence (OCA1A) or very low levels (OCA1B) of melanin pigment.
1. In OCA 1A (tyrosine negative OCA) there is absolute lack of tyrosinase activity.
2. OCA 1B (tyrosine positive OCA) has extremely reduced tyrosinase activity.
- Consequently, OCA 1B may develop some pigmentation as they grow older.
OCA1A clinical features?
- At birth: white hair, pinkish skin colour, blue grey iris and prominent red reflex.
- As they grow: no change in pigment, though hair may turn yellow due to UV keratin denaturation. No lentigines development.
- Associated features: photophobia, nystagmus, foveal hypoplasia, strabismus,
OCA1B clinical features?
- At birth: white hair, pinkish skin colour, blue grey iris and prominent red reflex
- As they grow older: hair may turn light yellow or golden blond, before becoming dark blond or dark brown in adulthood.
- Skin may develop lentigines and nevi during first few decades - Associated Features: photophobia, nystagmus, foveal hypoplasia, strabismus,
OCA2 clinical features?
- At Birth: may have some hair pigment; white, light/golden blond or brown. Pigmented birth marks may be present.
- As they grow older: increased pigmentation of the skin (freckles), hair (brown) and eyes (blue to light brown) tend to develop
- Associated factors: photophobia, nystagmus, foveal hypoplasia, strabismus - but less severe
Complications of OCA?
Extreme sensitivity to UVR leading to
1. Actinic keratoses
2. Basal cell carcinoma
3. SCC
Medical problems caused by lack of melanin?
- Sun damage of the skin leading to painful red skin (sun burn)
- Damaged cells may later become cancer cells
- Eyes
- Poor vision
- Photophobia: severe discomfort when exposed to light, which they try to avoid
Social problems?
- PWA called derogatory terms: mzungu, napweri
- Not considered humans
- Brutal attacks and killings
- Exclusion from getting social rights: jobs, education, social services
- Women divorced, abandoned when given birth to a child with albinism
Diagnosis?
- Made clinically based on skin and ocular features.
- Differentiating types not always possible clinically, so molecular analysis only accurate way towards specific diagnosis.
- Rarely necessary in daily clinic al practice
Histopathology?
- Normal melanocytes but with no melanin staining.
- Keratinocytes and other cells normal.