OMIM ID:
Retinitis Punctata Albescens
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Uniform white dots are symmetrically distributed in the midportion and periphery of the retina but the central portion of the macula is usually relatively spared in early stages of the disease. These flecks are present in the first decade of life increasing in density and covering larger areas of the retina in older individuals. Difficulties with night vision are also noted early and visual acuity may be compromised, in the range of 20/40. By the fifth and sixth decades there may be retinal pigment atrophy in the midperiphery and this eventually progresses to geographic atrophy of the macular RPE as the visual field becomes more constricted. The fundus in older individuals resembles that seen in retinitis pigmentosa with retinal vascular attenuation, frank bone spicule pigmentation, macular disease, and pallor of the optic nerves with significant loss of vision. The ERG shows reduction in scotopic responses and mild reductions in photopic amplitudes.
This form of flecked retina is sometimes considered to be a variant of fundus albipunctatus (136880). In favor of this argument are the observations in families in which some young members have the fundus picture of fundus albipunctatus (136880) while older ones with more advanced disease have all of the features of retinitis punctata albescens. Also supportive is the fact that mutations in RLBP1 have been identified in both conditions.
However, many individuals with fundus albipunctatus (136880) are described as having a stable disease with night blindness as the major symptom while many patients reported with retinitis albescens clearly have a more progressive and more serious disease with a fundus picture in late stages resembling retinitis pigmentosa. The relationship of these two conditions should become clearer once we learn more about the natural history of these rare disorders.
Systemic Features
No systemic abnormalities have been reported.
Genetics
Inheritance
This is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in RLBP1 (15q26.1). Parental consanguinity is frequently present. Mutations in the same gene are also responsible for Bothnia type retinal dystrophy (607475), fundus albipunctatus (136880), and occasional patients with classical retinitis pigmentosa.
Some authors consider retinitis punctata albescens to have an autosomal dominant pattern of transmission, perhaps based on the presence of white spots in the retina of parents. However, heterozygotes are always asymptomatic.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.