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.