Table 2.

Nonsyndromic Oculocutaneous Albinism and Ocular Albinism by Gene

Gene 1, 2Disorder% of All OCAComments
TYR OCA1
(OMIM 606933)		42%OCA1 is broadly divided into OCA1A & OCA1B:
  • OCA1A: absence or complete inactivity of TYR enzyme; severe reduction of retinal, iris, & skin pigmentation
  • OCA1B: reduced TYR enzyme activity (due to hypomorphic TYR variants); variable amounts of pigmentation, incl near normal cutaneous & hair pigment
OCA2 OCA2
(OMIM 611409)		28%
  • Phenotypic spectrum incl "brown" OCA. 3
  • OCA2 & TYRP1 pathogenic variants are the most common causes of albinism in sub-Saharan Africa.
TYRP1 OCA3
(OMIM 115501)		2.1%
  • Phenotype (previously described as "rufous" albinism) is characterized by red-bronze skin color, ginger-red hair, & blue or brown irides.
  • OCA3 is more common in African populations than in other populations (e.g., South Asian, European).
SLC45A2
(MATP)		 OCA4 11%
  • Most common OCA in Japan
  • Few affected persons have cutaneous & ocular hypopigmentation; most have normal visual acuity & foveal structure. 4
SLC24A5 OCA6
(OMIM 609802)		3%
  • Ocular features overlap w/other forms of OCA.
  • Typically, skin is hypopigmented w/ability to tan in some persons.
  • Hair color can range from white to brown.
LRMDA
(C10orf11)		OCA7
(OMIM 614537)		<1%
  • Only a few affected persons have been reported.
  • Significant phenotypic overlap exists w/other forms of OCA.
DCT
(TYRP2)		OCA8
(OMIM 191275)		<1%Rare; assoc w/mild hair & skin hypopigmentation
GPR143
(OA1)		OA1
(OMIM 300808)		7%
  • Clinically, only ocular hypopigmentation is present. However, the ocular phenotype of OA & OCA overlap.
  • In heterozygous females (i.e., carriers), "mud-splattered" fundus has been described due to interspersed regions of pigmentation.

OA = ocular albinism; OCA = oculocutaneous albinism

1.

Where applicable, former gene symbols are listed in parenthesis after the current HGNC-approved gene symbol.

2.

Genes are ordered by frequency of causation of OCA [Lasseaux et al 2018]; however, these are based on predominantly European populations. Variants in OCA2 and TYRP1 are more common in sub-Saharan Africa. SLC45A2 variants are more common in Japan.

3.

"Brown" OCA, described initially in Nigeria and Ghana and considered a separate entity based on early family studies, is now known to be part of the phenotypic continuum of OCA2-related OCA (see Nomenclature).

4.

From: Oculocutaneous Albinism and Ocular Albinism Overview

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