|
The subject of this report had Leber’s
congenital amaurosis and Coats’ response.
Leber’s congenital amaurosis (LCA), described by Theodor
Leber in 1869, is a disorder of congenital blindness associated
with nystagmus and variable fundus appearance.
GENETICS: LCA has
autosomal recessive
inheritance with a variable phenotypic expression. It is genetically
heterogeneous. For example, Camuzat et al. reported the
localization of an LCA1 gene to the short arm of chromosome 17
(17p13.1 between loci D17S938 and D17S1353) in a group of consanguineous
families of North African origin. LCA1 accounted for 8/15 LCA
families in this series. Perrault et al. ascribed some cases of
LCA1 to impaired production of retinal cGMP, with permanent closure
of cGMP-gated cation channels. This is caused by two missense
mutations (F589S) and two frameshift
mutations (nt 460 del C, nt 693 del C) of the retinal guanylate
cyclase gene. Mutations in RPE65 may also cause LCA.
SYMPTOMS/CLINICAL FINDINGS:
Patients with LCA have profound visual loss
shortly after birth, nystagmus, and minimally reactive pupils.
Hyperopia is the most common refractive
error, but myopia also occurs. Other frequent findings include
cataract, glaucoma,
keratoconus, photophobia, ptosis, strabismus, and the oculo-digital
sign of Franceschetti. Often, the fundus looks normal initially,
but retinitis
pigmentosa–like fundus features eventually develop,
ie, RPE hyperplasia in a bone spicule pattern, disc pallor, and
attenuated vascular caliber. Other fundus findings include macular
pseudo-coloboma, optic nerve atrophy, retinitis punctata albescens,
marbelized fundus, retinal vasculitis, bull’s eye lesion,
fundus changes similar to those seen with Senior-Loken syndrome,
and optic disc edema. Because of the varied phenotypic
presentation of LCA, the ERG plays an important role in the diagnosis
of this disorder. Markedly reduced or absent
ERG response under photopic and scotopic conditions is
characteristic.
ASSOCIATED CONDITIONS:
LCA can be associated with systemic
abnormalities, eg, deafness, skeletal anomalies,
osteopetrosis, Senior-Loken syndrome, polycystic kidney disease,
cardiomyopathy, neurological abnormalities, and mental retardation.
Consanguinity has been described among the parents of some patients.
ATYPICAL CLINICAL FINDING:
The patient had some features atypical for Leber’s congenital
amaurosis, such as moderately impaired
vision instead of severely impaired vision. These
features can be attributed to phenotypic heterogeneity of the
syndrome as the brother had typical features of Leber’s congenital
amaurosis such as severe visual loss and hyperopia. The normal
examination of the parents and one sibling supported the diagnosis
of recessive inheritance in this case. The history of consanguinity
may explain the occurrence of the condition in 2 of the 3 siblings.
The polymorphic appearance of the fundus in 2 siblings of the
same family was striking but has been described in cases of retinitis
pigmentosa. The proband had bilateral retinal telangiectasia with
intraretinal lipid and mild exudative retinal detachment, as well
as retinal neovascularization with localized traction retinal
detachment in one eye. The older sibling had no signs of retinal
telangiectasia, exudation, neovascularization, or retinal traction.
COATS' RESPONSE:
The phrase “Coats’ response” was introduced by
W. Banks Anderson in 1977 to describe a fundus picture similar
to Coats’ syndrome and characterized by exudative retinopathy
with aneurysmal and telangiectatic retinal vascular changes as
well as intraretinal and subretinal lipid deposits. Coats’
response differs from the syndrome described by George Coats in
1908 with regard to laterality, gender, age of onset, location
of the retinal changes, and pattern of inheritance. Although
Coats’ response is known to be associated with retinitis
pigmentosa, it has not previously been reported in association
with Leber’s congenital amaurosis, as far as we know.
TREATMENT
MODALITY: Laser photocoagulation,
cryotherapy, diathermy, and scleral buckling have been used to
induce regression of neovascular tissue or to manage fibrovascular
proliferation-induced retinal detachment. At
present, there are insufficient data to support definite conclusions
regarding the success rate of a particular type of treatment for
Coats’ response in retinitis pigmentosa. There are
no set guidelines for treatment. Koshibu et al. and Kajiwara et
al. have noted regression of pathology with photocoagulation,
whereas Schmidt and Faulborn, Yuguchi and Majima, and Ide et al.
have been unsuccessful. Schatanek et al. reported that the success
of laser therapy depends on early detection of Coats’-type
vascular abnormalities and early initiation of the treatment.
|
