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Electronegative Electroretinogram in Mucolipidosis IV
Shan M. Pradhan;
La-Ongsri Atchaneeyasakul, MD;
Binoy Appukuttan, PhD;
Robert N. Mixon, MA;
Trevor J. McFarland;
Andrea M. Billingslea;
David J. Wilson, MD;
J. Timothy Stout, MD, PhD;
Richard G. Weleber, MD
Arch Ophthalmol. 2002;120:45-50.
Objective To demonstrate the progression of electroretinographic (ERG) findings
in mucolipidosis IV.
Methods Two patients with mucolipidosis IV were examined clinically and their
condition was followed up for ophthalmic manifestations of the disease. Electroretinograms
were performed on both patients, and conjunctival biopsy specimens were analyzed
for characteristic ultrastructural inclusion bodies using light and electron
microscopy. Genomic DNA isolated from peripheral blood was screened for 2
major founder mutations in the ML4 gene using polymerase
chain reaction and restriction fragment length polymorphism analyses. Haplotypes
were confirmed by automated sequencing of polymerase chain reaction products.
Results In patient 1, an ERG obtained at 12 months of age showed mildly subnormal
amplitude of rod-mediated and cone-mediated responses and significantly prolonged
rod and cone b-wave implicit times. An ERG obtained when the patient was 6.6
years old disclosed marked progression with greater loss of b-wave than a-wave
responses to rod-and-cone–mediated activity. Scotopic ERG at the highest
intensity was electronegative in configuration. In patient 2, ERG showed minimal
rod-mediated responses, severely subnormal cone-mediated responses, and prolonged
cone b-wave implicit times. Again, electronegative configuration of the scotopic
bright flash response indicated greater disturbance of b-wave generators.
Conclusions Novel ERG findings in 2 cases of mucolipidosis IV are reported with
associated clinical courses, histopathologic abnormality, and genetic studies.
In both cases ERGs demonstrate an electronegative configuration, suggesting
that the primary retinal disturbance in mucolipidosis IV may occur at or proximal
to the photoreceptor terminals.
From the Keck School of Medicine, University of Southern California,
Los Angeles (Ms Pradhan); the Department of Ophthalmology, Siriraj Hospital,
Mahidol University, Bangkok, Thailand (Dr Atchaneeyasakul); Department of
Molecular and Medical Genetics, Oregon Health & Science University (Drs
Stout and Weleber); and the Department of Ophthlmology, Case Eye Institute,
Oregon Health & Science University (Drs Appukuttan, Wilson, Stout, and
Weleber, Messrs Mixon and McFarland, and Ms Billingslea), Portland.
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