Juvenile Neuronal Ceroid Lipofuscinosis (Batten Disease) CLN3 Mutation (Chrom 16p11.2) with Different Phenotypes in a Sibling Pair and Low Intensity in vivo Autofluorescence

Juvenile Batten Disease (CLN3): Detailed Ocular Phenotype, Novel Observations, Delayed Diagnosis, Masquerades, and Prospects for Therapy

Purpose

To characterize the retinal phenotype of juvenile neuronal ceroid lipofuscinosis (JNCL), highlight delayed and mistaken diagnosis, and propose an algorithm for early identification.

Design

Retrospective case series.

Participants

Eight children (5 female) with JNCL.

Methods

Review of clinical notes, retinal imaging including fundus autofluorescence and OCT, electroretinography (ERG), and both microscopy and molecular genetic testing.

Main Outcome Measurements

Demographic data, signs and symptoms, visual acuity (VA), fundus autofluorescence and OCT findings, ERG phenotype, and microscopy/molecular genetics.

Results

Participants presented with rapid bilateral vision loss over 1 to 18 months, with mean VA deteriorating from 0.44 logarithm of the minimum angle of resolution (logMAR) (range, 0.20–1.78 logMAR) at baseline to 1.34 logMAR (0.30 logMAR - light perception) at last follow-up. Age of onset ranged from 3 to 7 years (mean, 5.3 years). The age at diagnosis of JNCL ranged from 7 to 10 years (mean, 8.3 years). Six children displayed eccentric fixation, and 6 children had cognitive or neurologic signs at the time of diagnosis (75%). Seven patients had bilateral bull’s-eye maculopathy at presentation. Coats-like exudative vasculopathy, not previously reported in JNCL, was observed in 1 patient. OCT imaging revealed near complete loss of outer retinal layers and marked atrophy of the nerve fiber and ganglion cell layers at the central macula. An electronegative ERG was present in 4 patients (50%), but with additional a-wave reduction, there was an undetectable ERG in the remaining 4 patients. Blood film microscopy revealed vacuolated lymphocytes, and electron microscopy showed lysosomal (fingerprint) inclusions in all 8 patients.

Conclusions

In a young child with bilateral rapidly progressive vision loss and macular disturbance, blood film microscopy to detect vacuolated lymphocytes is a rapid, readily accessible, and sensitive screening test for JNCL. Early suspicion of JNCL can be aided by detailed directed history and high-resolution retinal imaging, with subsequent targeted microscopy/genetic testing. Early diagnosis is critical to ensure appropriate management, counseling, support, and social care for children and their families. Furthermore, although potential therapies for this group of disorders are in early-phase clinical trial, realistic expectations are that successful intervention will be most effective when initiated at the earliest stage of disease.

[Juvenile neuronal ceroid lipofuscinosis. Ophthalmologic findings and differential diagnosis]

Neuronal ceroid lipofuscinoses (NCL) are a heterogeneous group of neurodegenerative diseases with mostly autosomal recessive inheritance whose common feature is the intralysosomal accumulation of ceroid lipofuscin. With varying manifestation ages the diseases result in cognitive and motor deterioration, epilepsy, diffuse retinal degeneration, and eventually death. Juvenile ceroid lipofuscinosis (JNCL, CLN3, Batten disease) has the distinctive feature that the ophthalmologic symptoms precede the neurologic symptoms by several years, and thus the ophthalmologist plays a central role in early diagnosis. Important clinical signs of JNCL include bull's eye maculopathy, severely reduced Ganzfeld ERG already at initial presentation, and unusually rapid progression of the functional decline. If JNCL is clinically suspected the diagnosis can be made by means of a standard blood smear and confirmed by genetic detection of the mutation. Although causal therapeutic options are currently only in the developmental stage, early diagnosis by the ophthalmologist is of utmost importance to allow for medical and educational support of the affected child and for adequate counseling of the parents.

Autofluorescence and infrared retinal imaging in patients and obligate carriers with neuronal ceroid lipofuscinosis

PURPOSE

To measure fundus autofluorescence (FAF) in patients and obligate carriers with Neuronal Ceroid Lipofuscinosis (NCL) and document fundus abnormalities in NCL patients using standard retinal photography and confocal infra-red (IR) imaging.

METHODS

Twenty-seven patients with NCL, 50 obligate carriers of NCL, and 19 controls were imaged in IR and FAF modes by a confocal scanning laser opthalmoscope (HRA II, Heidelberg-Engineering, Inc). FAF intensities were referenced to the mean and standard deviation at the optic disk to remove inter-subject variance and then quantified along the horizontal and vertical meridians.

RESULTS

For NCL subjects, FAF images were successfully obtained in 16 eyes (9 of 27 subjects). Of these, 11 eyes had severely reduced or extinguished FAF and 5 eyes (3 subjects) could be analyzed along the meridians. An NCL subject with bilateral bull's eye maculopathy showed overall increased FAF, the remaining 3 eyes had advanced retinal degeneration and showed reduced FAF. Four patterns of macular disease were observed: 1) bull's eye atrophy 2) retinal pigment epithelium (RPE) dropout without pigmentary alterations, 3) RPE dropout with pigmentary alterations, 4) RPE dropout with pigmentary alterations and retinal flecks. Standard photography revealed focal retinal flecks in addition to severe retinal atrophy, RPE dropout, pigmentary clumping, and constricted vessels. Linear striations near the optic disc were highlighted by IR imaging. Topographical comparison of images demonstrated the focal flecks were not hyperfluorescent while the linear striations showed slight increases in FAF. For obligate carriers, FAF profiles were similar to controls with a mild increase in mean FAF intensity.

CONCLUSIONS

Patients with NCL show increases in retinal fluorophores in early stages and decreases in FAF in late stages of the disease. Obligate carriers of NCL have mildly elevated FAF but this finding is not a specific measure of the carrier state.

Juvenile neuronal ceroid lipofuscinosis (JNCL) and the eye

Juvenile neuronal ceroid lipofuscinoses, or Batten disease, is the most common type of NCL in the United States and Europe. This devastating disorder presents with vision failure and progresses to include seizures, motor dysfunction, and dementia. Death usually occurs in the third decade, but some patients die before age twenty. Though the mechanism of visual failure remains poorly understood, recent advances in molecular genetics have improved diagnostic testing and suggested possible therapeutic strategies. The ophthalmologist plays a crucial role in both early diagnosis and documentation of progression of juvenile neuronal ceroid lipofuscinoses. We update Batten disease research, particularly as it relates to the eye, and present various theories on the pathophysiology of retinal degeneration.

The negative ERG: clinical phenotypes and disease mechanisms of inner retinal dysfunction

Inner retinal dysfunction is encountered in a number of retinal disorders, either inherited or acquired, as a primary or predominant defect. Fundus examination is rarely diagnostic in these disorders, although some show characteristic features, and careful electrophysiological assessment of retinal function is needed for accurate diagnosis. The ERG in inner retinal dysfunction typically shows a negative waveform with a preserved a-wave and a selectively reduced b-wave. Advances in retinal physiology and molecular genetics have led to a greater understanding of the pathogenesis of these disorders. This review summarizes current knowledge on normal retinal physiology, the investigative techniques used and the range of clinical disorders in which there is predominantly inner retinal dysfunction.

A novel microdeletion at 16p11.2 harbors candidate genes for aortic valve development, seizure disorder, and mild mental retardation

Many multiple congenital anomalies (MCA) are caused by recombination between homologous segmental duplications. In this report, we describe a novel "de novo" microdeletion in male monozygotic twins presenting with aortic valve abnormality, seizure disorder, and mild mental retardation. Using array based comparative genomic hybridization, we mapped the microdeletion to the short arm of chromosome 16 at 16p11.2 and refined it using hemizygosity mapping to about 593 kb, a region that overlaps with 24 genes. The most probable mechanism for this microdeletion is through a specific intrachromosomal recombination between two, nearly identical, segmental duplications each spanning 147 kb that are flanking the microdeletion. Based on the phenotypes presented in the twins and what is known about the genes within the 16p11.2 microdeletion, we identified several genes that are strong candidates for the normal development of the aortic valve, as well as the development of seizure disorder and mental retardation.

Batten disease: features to facilitate early diagnosis

AIMS

To ascertain the clinical and electrophysiological features in patients with juvenile neuronal ceroid lipofuscinosis (jNCL/Batten disease) and to identify those features that facilitate early diagnosis.

METHODS

Nine patients with jNCL were identified retrospectively and their case notes reviewed. All had undergone an extensive clinical examination, including electrophysiology. Blood and molecular genetic testing confirmed the diagnosis.

RESULTS

Age at onset ranged from 4-8 years. At presentation, two of nine patients had normal fundi; only two of nine patients had a bull's eye maculopathy. The electroretinogram (ERG) findings in this series included undetectable rod specific ERGs, an electronegative maximal response, reduced and delayed cone flicker ERGs, reduction in the b:a ratio in the photopic single flash ERG, and an undetectable pattern ERG. Vacuolated lymphocytes on peripheral blood film testing were present in eight of nine patients. Five of eight patients were homozygous for the 1.02 kb deletion on the CLN3 gene on molecular genetic testing; two of eight patients were heterozygous for that deletion.

CONCLUSION

jNCL should be considered in children of 10 years and under presenting with visual loss and fundal changes ranging from normal through to pigmentary/atrophic changes or a bull's eye maculopathy. Electrophysiology may suggest jNCL. Although currently untreatable, early diagnosis is important to institute appropriate counselling and support.