Novel CLN1 mutation with atypical juvenile neuronal ceroid lipofuscinosis

We detected a novel CLN1 gene mutation (p.Arg151X, heterogenous) in a 12-year-old boy. Low level of palmitoyl protein thioesterase and granular inclusion pattern in lymphocytes were also consistent with infantile Neuronal ceroid lipofuscinosis (INCL). However, the clinical phenotype was that of atypical juvenile neuronal ceroid lipofuscinosis (JNCL) and consisted of progressive visual loss from the age of 8 years. His visual acuity was 6/60 in both eyes at first presentation, 6/36 one month later, then 6/6 (right eye), and 6/60 (left eye) 6 months later. However, after 4 months, visual acuity dropped to 6/60 in both eyes and at last follow-up, it was 6/60 (right eye) and 3/60 (left eye). Visual hallucinations were also reported. Persistent normal fundi findings, normal electroretinogram (ERG), and delayed visual evoked potentials (VEP) were suggestive of non-retinal adolescence form/atypical JNCL. Visual loss in JNCL is secondary to retinal dystrophy. Our observations suggest that JNCL should be considered in any children presenting with bilateral progressive visual loss even with normal fundi and/or delayed VEP. Electron microscopy of buffy coat and palmitoyl protein thioesterase enzyme study are useful tools in diagnosis. Pertinent issues regarding clinical symptomatology, ophthalmologic findings, and laboratory results are discussed.