Oculocutaneous albinism (OCA) is a group
of inherited disorders of melanin
biosynthesis characterized by a generalized
reduction in pigmentation of hair, skin and
eyes. The prevalence of all forms of
albinism varies considerably worldwide and
has been estimated at approximately
1/17,000, suggesting that about 1 in 70
people carry a gene for OCA. The clinical
spectrum of OCA ranges, with OCA1A being
the most severe type with a complete lack
of melanin production throughout life, while
the milder forms OCA1B, OCA2, OCA3 and
OCA4 show some pigment accumulation
over time.
We report a case of a 27-years-old white girl that presented
herself in the emergency room with a history of decreased visual
acuity of both eyes. She had hypopigmentation of the hair, and
the skin was white and does not tan. Her parents and siblings
have no ocular abnormalities and they have always been dark
haired with dark brown eyes, and they tan normally. On
examination, best corrected visual acuity (BCVA) was 20/30 and
20/50 over the right and left eye, respectively. She presented with
exotropia, and reduced stereoscopic vision. The iris was
hypopigmented but iris translucency was not evident on slit lamp
examination. Fundus examination showed hypopigmented fundi
with absence of the usual foveal hyperpigmentation and macular
and foveal reflexes. Optic coherence tomography (OCT) revealed
reduced thickness of all retinal layers, foveal hypoplasia, and no
foveal pit was found.
Among disorders where albinism is part of a larger syndrome are Hermansky-Pudlak syndrome, Chediak-Higashi
syndrome, Griscelli Syndrome, and Waardenburg Syndrome type II. All can be distinguished on the basis of clinical
and biochemical criteria. The patient did not exhibit any characteristic of none of these syndromes. The diagnosis of
OCA was done based on clinical findings of hypopigmentation of the skin and hair, in addition to the characteristic
ocular symptoms and test results. However, due to the clinical overlap between the OCA subtypes, molecular
diagnosis is necessary in order to establish the gene defect and thus the OCA subtype. The molecular diagnosis is
also essential for genetic counseling.
Sílvia Monteiro MD, Inês Casal MD, Luís Miguel Neves MD, Mafalda Macedo MD, Maria João Furtado MD, Angelina Meireles MD
Ophthalmology Department, Centro Hospitalar do Porto, EPE, Porto, Portugal
Department Director: Pedro Menéres MD
On visual fields a bilateral nasal constriction was found. Pattern onset visually evoked potentials (VEPs) were
recorded and the chiasmal coefficient was evaluated to detect misrouting (Fig.3). The VEP recordings showed the
earliest answer over the right hemisphere for the left eye, and over the left hemisphere for the right eye. The VEPs
were indicative of chiasmal misrouting, a characteristic finding in OCA.