Optic nerve dysfunction in familial dysautonomia

Selective retinal ganglion cell loss in familial dysautonomia

To define the retinal phenotype of subjects with familial dysautonomia (FD). A cross-sectional study was carried out in 90 subjects divided in three groups of 30 each (FD subjects, asymptomatic carriers and controls). The study was developed at the Dysautonomia Center, New York University Medical Center. All subjects underwent spectral domain optical coherence tomography (OCT) and full neuro-ophthalmic examinations. In a subset of affected subjects, visual evoked potentials and microperimetry were also obtained. We compared the retinal nerve fiber layer (RNFL) thickness from OCT between the three groups. OCT showed loss of the RNFL in all FD subjects predominantly in the maculopapillary region (63 % temporally, p < 0.0001; and 21 % nasally, p < 0.005). RNFL loss was greatest in older FD subjects and was associated with decreased visual acuity and color vision, central visual field defects, temporal optic nerve pallor, and delayed visual evoked potentials. Asymptomatic carriers of the FD gene mutation all had thinner RNFL (12 % globally, p < 0.005). OCT and clinical neuro-ophthalmological findings suggest that maculopapillary ganglion cells are primarily affected in FD subjects, leading to a specific optic nerve damage that closely resembles mitochondrial optic neuropathies. This raises the possibility that reduced IKAP levels may affect mitochondrial proteins and their function in the nervous system, particularly in the retina.

IKAP expression levels modulate disease severity in a mouse model of familial dysautonomia

Hereditary sensory and autonomic neuropathies (HSANs) encompass a group of genetically inherited disorders characterized by sensory and autonomic dysfunctions. Familial dysautonomia (FD), also known as HSAN type III, is an autosomal recessive disorder that affects 1/3600 live births in the Ashkenazi Jewish population. The disease is caused by abnormal development and progressive degeneration of the sensory and autonomic nervous systems and is inevitably fatal, with only 50% of patients reaching the age of 40. FD is caused by a mutation in intron 20 of the Ikbkap gene that results in severe reduction in the expression of its encoded protein, inhibitor of kappaB kinase complex-associated protein (IKAP). Although the mutation that causes FD was identified in 2001, so far there is no appropriate animal model that recapitulates the disorder. Here, we report the generation and characterization of the first mouse models for FD that recapitulate the molecular and pathological features of the disease. Important for therapeutic interventions is also our finding that a slight increase in IKAP levels is enough to ameliorate the phenotype and increase the life span. Understanding the mechanisms underlying FD will provide insights for potential new therapeutic interventions not only for FD, but also for other peripheral neuropathies.

Clinical neuro-ophthalmic findings in familial dysautonomia

BACKGROUND

To define the clinical neuro-ophthalmic abnormalities of patients with familial dysautonomia (FD).

METHODS

Sixteen patients (32 eyes) with the clinical and molecular diagnoses of FD underwent thorough neuro-ophthalmic clinical evaluation.

RESULTS

Visual acuity ranged from 0.05 to 1.0 decimal units and was reduced in 15 of 16 patients. Mild to moderate corneal opacities were found in most patients but were visually significant in only 2 eyes. Red-green color vision was impaired in almost all cases. Depression of the central visual fields was present on automated visual fields in all patients, even in those with normal visual acuity. Temporal optic nerve pallor was present in all cases and was associated with retinal nerve fiber layer loss in the papillomacular region. Various ocular motility abnormalities also were observed.

CONCLUSION

Patients with FD have a specific type of optic neuropathy with predominant loss of papillomacular nerve fibers, a pattern similar to other hereditary optic neuropathies caused by mutations either in nuclear or in mitochondrial DNA, affecting mitochondrial protein function. Defects of eye movements, particularly saccades, also appear to be a feature of patients with FD.

Piggyback cosmetic contact lens as an occlusion therapy in a patient with familial dysautonomia

PURPOSE

The purpose of this case report is to explore the treatment of ocular and visual complications secondary to familial dysautonomia (Riley–Day syndrome) on an 8 month-old baby. Treatments for corneal scarring,ocular protection, and amblyopia were achieved by fitting a scleral lens with a unique piggyback combination involving a cosmetic soft contact lens.

METHOD

The patient was seen in February 2008, on referral from a corneal specialist, for a scleral lens fitting. This case was comanaged from Université de Montréal with the help of the Boston Foundation for Sight.Examination revealed a right cornea with opacities. We planned to use scleral lenses to treat this eye and to protect the other one. Although the patient's ocular condition did improve, some concerns arose about potential impact on her visual development. Our treatment for amblyopia involved the use of atropine in both eyes and penalization of the good eye with a cosmetic opaque contact lens that we fitted onto a piggyback system over the scleral lens. The rationale behind this approach is explained in this article.

RESULT

After the contact lens was fitted and after penalization and atropinization,the baby's visual condition improved. Time will tell to what degree this treatment is effective.

CONCLUSION

Familial dysautonomia is a challenging condition for the eye because of the presence of alacrymia and lack of corneal sensitivity. Scleral contact lenses and cosmetic contact lenses offer a unique way of addressing many issues, such as corneal healing and amblyopia, raised in this case report. These devices may be considered for any other case that requires corneal tissue healing and visual development.

A world without pain or tears

The world of the child with familial dysautonomia (FD), a genetic disorder affecting development of the sensory and autonomic nervous system, is not idyllic. However, over the last 35 years advances in supportive treatments have improved morbidity and mortality. Recent genetic breakthroughs have further expanded thinking about this disorder and suggested innovative approaches to modifying genetic expression. This article reviews the current supportive treatment modalities and their rationale, as well as the suggested new treatments that may alter the function and prognosis of an individual affected with FD.

Familial dysautonomia

Familial dysautonomia (FD) is a neurodevelopmental genetic disorder within the larger classification of hereditary sensory and autonomic neuropathies, each caused by a different genetic error. The FD gene has been identified as IKBKAP. Mutations result in tissue-specific expression of mutant IkappaB kinase-associated protein (IKAP). The genetic error probably affects development, as well as maintenance, of neurons because there is neuropathological and clinical progression. Pathological alterations consist of decreased unmyelinated and small-fiber neurons. Clinical features reflect widespread involvement of sensory and autonomic neurons. Sensory loss includes impaired pain and temperature appreciation. Autonomic features include dysphagia, vomiting crises, blood pressure lability, and sudomotor dysfunction. Central dysfunction includes emotional lability and ataxia. With supportive treatment, prognosis has improved greatly. About 40% of patients are over age 20 years. The cause of death is usually pulmonary failure, unexplained sudden deaths, or renal failure. With the discovery of the genetic defect, definitive treatments are anticipated.

Early-onset multisystem degeneration with central motor, autonomic and optic nerve disturbances: unusual Riley-Day syndrome or new clinical entity?

We report a 21-year-old woman presenting with a slowly progressive tetraparesis, optic nerve atrophy on both sides, and autonomic disturbances since early childhood. The patient has been carefully followed up for 5 years with clinical and ancillary investigations. The results and the time course strongly suggest an underlying degenerative syndrome affecting parts of three major systems: autonomic, motor and visual. Some symptoms resemble familial dysautonomia (FD, Riley-Day syndrome), however, hallmarks of FD, such as absence of fungiform papillae of the tongue, abnormal reaction on intradermal histamine injection, absent tendon reflexes, are missing, and central motor disturbances have not been described in FD. We consider this syndrome a slowly progressive multisystemic degeneration with two unusual hitherto unreported features: the combination of affected systems (autonomic and motor systems, optic nerves), and the early onset.