Heterogeneous group of hereditable diseases of the
melanin pigmentary system.
Type IA = Tyrosinase negative albinism
Type IB = Yellow mutant albinism
Type IC = Platinum albinism
Type II = Tyrosinase-positive albinism
Type III = Minimal pigment albinism
Type IV = Brown albinism
Type V = Rufus albinism
Type VIA = Hermansky-Pudlak syndrome (HPS)
Type VIB = Chediak-Higashi syndrome
Type VII = Autosomal dominant albinism
Type I = Albinism autosomal recessive
Type II = Albinism Forsius-Ericksson syndrome
Type III = Albinism with sensorineural deafness
Type IV = Tietz syndrome
Type I is an autosomal recessive disorder that
is associated with a defect in the gene encoding for tyrosinase. Most of the
other types are either autosomal dominant or sex-linked variants and are
believed to be tyrosinase positive. Albinism does exist in all racial
Oculocutaneous albinism is caused by congenital
melanin metabolism defects. The common defect linking all forms of albinism
affects the formation of melanosomes. Melanin biosynthesis is initiated by
the catalytic oxidation of tyrosine to dopa (3-4-dihydroxyphenylalanine, a
melanin precursor) by tyrosinase. This reaction requires dopa as a cofactor.
Albinos are either tyrosinase positive or negative, and all subtypes can be
identified by clinical and biochemical means. The degree of melanin
depletion is used to classify the disease into different subtypes.
Both ocular and cutaneous tissues are affected in this
form of albinism, with diffuse leukodermia and variable pilosity disorders.
The disease is potentially severe because patients may develop cutaneous
carcinoma or melanoma with more or less early onset. Two types of
oculocutaneous albinism have been identified, depending on the presence or
absence of tyrosinase. The tyrosinase-negative form, also called
complete albinism type I, is the
most severe. Hypoplasia of the fovea, translucent iris, photophobia,
nystagmus, decreased visual acuity, and inability of binocular vision are
crucial to the diagnosis.
In addition to the features described, patients
with oculocutaneous albinism have decreased pigmentation of skin and hair,
whereas patients with ocular albinism have disease limited to the eyes.
Albinism is not associated with impaired intelligence. In fact, an
association with higher intellect may exist. Patients should be instructed
to shield their eyes and skin from the sun.
There are no specific problems for
most types of oculocutaneous albino patients undergoing surgery or
anesthesia. However, patients with Chediak-Higashi Syndrome (Type VIB)
or Hermansky-Pudlak Syndrome (Type VIA) have considerable anesthetic
considerations. In general terms, all other types require routine
preoperative evaluation. However, evaluation of coagulation
parameters is recommended.
Provided that Hermansky-Pudlak syndrome
and Chediak-Higashi syndrome could be excluded,
there should be no specific
anesthetic contraindications. Occasionally, patients complain of photophobia
because of the brightness of the light in the operating room.