Abstract
Purpose:
To describe novel retinal and optic nerve findings in three siblings with adult-onset Chediak-Higashi syndrome (CHS).
Methods:
Three siblings (sibling 1 - 40 yo woman, sibling 2 - 38 yo man, sibling 3 - 32 yo man) presented with a multifocal neurologic degenerative disorder. The diagnosis of CHS was confirmed by sequencing of the entire coding region of the LYST gene. Evaluation included clinical ophthalmologic and neurologic examination, evaluation of color vision (Ishihara plates) and contrast sensitivity (Pelli-Robson charts), Goldmann perimetry, fundus photography, spectral-mode OCT, electroretinography (ERG) and visual evoked potential testing (VEP).
Results:
Sequencing of the entire coding region of LYST identified homozygosity for a novel six base pair in-frame deletion in exon 43 (c.9827_9832ATACAA), predicting the loss of asparagine and threonine residues from the LYST protein transcript (p.Asn3276_Thr3277del). Neurological findings included cognitive decline, peripheral neuropathy, cerebellar ataxia, myelopathy, and parkinsonism. All siblings were visually asymptomatic. Visual acuity was near-normal in all. Color vision was severely impaired in sibling 1, normal in siblings 2 and 3. Contrast sensitivity was moderately reduced in all. Optic nerves were severely pale in sibling 1, mildly pale in sibling 2, and normal in sibling 3. Goldmann fields revealed central field loss in all, with additional peripheral constriction in sibling 2. Ocular albinism, typical of CHS, was absent. Ganzfeld ERGs were normal, but VEPs were reduced and P-100 latencies delayed. Spectral-mode macular OCT imaging was notable for markedly enhanced reflections from the photoreceptor-RPE interdigitation zone. This OCT abnormality was also noted in the patients’ father, who was free from visual impairment and heterozygous for the pathogenic deletion. Nerve fiber layer OCT revealed thinning in siblings 1 and 2.
Conclusions:
Reduced contrast sensitivity, impaired color vision, and visual field constriction are reported in three siblings, homozygous for a novel LYST mutation, with attenuated Chediak-Higashi syndrome. Classical CHS features of infantile-onset oculocutaneous albinism and immunodeficiency were absent in our patients. Anatomic and physiologic optic nerve involvement, previously unreported to our knowledge in CHS, is observed in our patients, and an unusual enhancement of the photoreceptor-RPE interdigitation zone is noted.
Keywords: 613 neuro-ophthalmology: optic nerve •
507 electrophysiology: clinical •
550 imaging/image analysis: clinical