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Sotos’ syndrome may be associated with optic disc pallor and retinal atrophy
A case of a young Japanese man who had experienced febrile convulsions since age 1 was documented.
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TOKYO — Sotos’ syndrome, an extremely rare genetic disorder characterized by excessive growth before and after birth, may be associated with optic disc pallor and retinal atrophy. A case report of a 22-year-old Japanese man who was diagnosed with Sotos’ syndrome at age 3 recently appeared in the American Journal of Ophthalmology.
“We thought the man’s optic disc pallor and retinal atrophy were induced by antiepileptic drugs or associated with Sotos’ syndrome,” said first author Kenji Inoue, MD, PhD, a former resident in the department of ophthalmology at the University of Tokyo Branch Hospital here. “Such ocular disorders as optic disc pallor and retinal atrophy are thought to be induced by Sotos’ syndrome. The literature also suggests an association between antiepileptic drugs and bilateral optic neuropathy.”
Children affected by Sotos’ syndrome, also referred to as cerebral gigantism syndrome, may exhibit characteristic facial differences and developmental delays. This particular patient, though, did not have a familial history of genetic factors for Sotos’ syndrome. “He had a body weight of 3,500 g and a length of 52 cm at birth,” Dr. Inoue said. By 6 months, “he had achieved a height of +2 standard deviation, which is a sign of cerebral gigantism.”
The patient also had experienced febrile convulsions since age 1 and epilepsy since age 5 and is considered mentally retarded. “Examinations at our outpatient facility revealed that his IQ was 56 at age 14,” Dr. Inoue said. Mental retardation is a hallmark of Sotos’ syndrome, affecting 84% of diagnosed individuals, with a median IQ of 72.
Bilateral optic atrophy
The young man presented at the University of Tokyo Branch Hospital with a diagnosis of bilateral optic atrophy. The horizontal corneal diameter was 13 mm, and intraocular pressure was 10 mm Hg in both eyes. “Visual acuity was 20/20 in both eyes, with a refraction of –0.75 D in the right eye and –0.50 D in the left eye,” Dr. Inoue said.
Keratometry measurements revealed 40.5 D (8.33 mm) in both eyes. “The axial length was 25.9 mm in the right eye and 25.5 mm in the left eye,” he said. The patient’s optic disc was also pale in both eyes.
“The man’s retinal vessels were attenuated, and small white spots were found on the retina,” but the results of a Goldman visual field test were normal. “Because the patient had normal visual acuity and fields, we did not prescribe any drugs,” Dr. Inoue told Ocular Surgery News. The patient’s visually evoked potential to flash stimuli indicated extended latent times and normal amplitudes.
Antiepileptic connection
The ocular signs in this man could be attributed to the use of antiepileptic drugs. “Our patient had been prescribed antiepileptic drugs such as valproic acid and phenobarbital for 17 years,” Dr. Inoue said. In a 1989 article in Neuro-ophthalmology, Homma et al reported that chronic phenobarbital therapy may induce bilateral optic neuropathy. Ohtagaki et al reported an association between metaphyseal dysplasia and intracranial calcifications, epilepsy and optic atrophy in Brain Development in 1997.
“Considering the fact that our patient also had megalophthalmos, normal visual acuity and fields, it is more likely that his optic disc pallor was induced by Sotos’ syndrome, not by the antiepileptic drugs,” said Dr. Inoue, who is now affiliated with the department of ophthalmology at Nadogaya Hospital.
Ocular findings
Patients with Sotos’ syndrome are known to have several ocular conditions, including cataracts, megalophthalmos, hypoorbitism, strabismus (esotropia, exotropia, vertical deviation), nystagmus, iris hypoplasia, megalocornea, hyperopia and retinal dystrophy.
In Helvetica Paediatrica Acta in 1982, Livieri et al reported on a patient with Sotos’ syndrome who had pale optic discs, normal retinal vessels and alterations of the retinal pigment (both in the pigment and peripherally).
“That patient’s visual fields were normal, but his electroretinogram revealed reduced amplitudes. His visual evoked responses to flash stimuli also showed normal latent time, but again there were reduced amplitudes,” Dr. Inoue said.
There has also been a published report of a family with Sotos’ syndrome. “However, in our case, the patient’s parents were not suffering from Sotos’ syndrome,” he said.
There are approximately 150 cases worldwide of Sotos’ syndrome. Risk factors are mostly sporadic, but there are some autosomal dominant and autosomal recessive forms. The pathogenesis is also unknown, although abnormal dermatographics and large birth size suggest a prenatal abnormality. In addition, an unidentified growth-stimulating material may play a role. Characteristic features of Sotos’ syndrome include gigantism, prominent forehead, high-arched palate, hypertelorism and an arm span greater than height.
For Your Information:
- Kenji Inoue, MD, PhD, can be reached at Department of Ophthalmology, Nadogaya Hospital, 687-4 Nadogaya, Kashiwa-shi, Chiba, 227-0032, Japan; +(81) 47-67-8336; fax: +(81) 471-63-7433; e-mail: inoue-k@fd5.so-net.ne.jp. Dr. Inoue has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
References:
- Homma K, Wakakura M, Ishikawa S. A case of phenobarbitol-induced optic neuropathy. Neuro-ophthalmol. 1989;9:357-360.
- Inoue K, Kato S, et al. Optic disc pallor and retinal atrophy in Sotos’ syndrome (cerebral gigantism). Am J Ophthalmol. 2000;130(6):853-854.
- Livieri C, Gelmi CG, et al. Retinal degeneration in Sotos’ syndrome. Helv Paediat Acta. 1982;37:93-94.
- Ohtagaki A, Hara T, et al. Intracranial calcifications, epilepsy and optic atrophy associated with metaphyseal dysplasia: a case report. Brain Dev. 1997;19:414-417.