IQCB1 (NPHP5)-retinopathy: Clinical and Genetic Characterization and Natural History

PURPOSE

To describe the clinical and genetic features, and explore the natural history of retinopathy associated with IQCB1 variants in children and adults with retinopathy.

DESIGN

Retrospective cohort study at a single tertiary care referral center.

METHODS

The study recruited 19 patients with retinopathy, harboring likely disease-causing variants in IQCB1. Demographic data and clinical presentation, best corrected visual acuity (BCVA), fundus appearance, optical coherence tomography (OCT) and autofluorescence features, electroretinography (ERG) and molecular genetics are reported.

RESULTS

Ten patients had BCVA better than 1.0 LogMAR, and BCVA remained stable till the last review. Seven patients had a vision of hand movements or worse in at least one eye at presentation. There was no correlation found between age of onset and severity of vision loss. Nine patients (47.4%) had a diagnosis of end-stage renal failure at presentation. The other 10 patients (52.6%) had a diagnosis of non-syndromic IQCB1-retinopathy and maintained normal renal function until the last follow-up. The mean age at diagnosis of renal failure was 26.3 ±19.8 years. OCT showed ellipsoid zone (EZ) disruption with foveal sparing in 8/13 patients. All patients had stable OCT findings. Full-field ERGs in four adults revealed a severe cone-rod dystrophy and three children had extinguished ERGs. We identified 17 IQCB1 variants, all predicted to cause loss of function.

CONCLUSION

IQCB1-retinopathy is a severe early-onset cone-rod dystrophy. The dissociation between severely decreased retinal function and relative preservation of retinal structure over a wide age window makes the disease a candidate for gene therapy.

Potpourri of retinopathies in rare eye disease - A case series

This case series describes the ocular and retinal manifestations of rare eye diseases in systemic syndromes. This observational case series consists of five patients with varied ophthalmic manifestations and documentation of imaging in rare pediatric and adult retinopathies. Two patients had Kearns Sayre syndrome (KSS) based on the classical triad of external ophthalmoplegia, pigmentary retinopathy, and onset before 20 years of age. In one patient of KSS, the mitochondrial retinopathy was seen in an asymmetric pattern, and the second patient presented with KSS after being mis-diagnosed as myasthenia gravis elsewhere. A case of Senior Loken syndrome in pediatric age is described in this series with varied ophthalmic manifestations ranging from retinitis pigmentosa to orbital abscess. This series also enlightens features of Hallervorden Spatz syndrome presenting with bull's eye maculopathy and a case of spino-cerebellar ataxia type 7 presenting with pigmentary retinopathy.

Ciliopathy: Senior-Løken Syndrome

Senior-Løken syndrome is a rare autosomal recessive disease with a prevalence of 1:1,000,000. Retinopathy may progress as Leber congenital amaurosis (LCA), retinitis pigmentosa (RP), or sector RP (Figs. 34.1 and 34.2). Onset of photophobia, nystagmus, and hyperopia can occur in the first few years of life or later in childhood. Patients experience nephronophthisis, characterized by cystic kidney disease (medullary cystic kidney disease), reduced concentrating ability, and chronic tubulointerstitial nephritis, which progresses to end-stage renal disease. Hypertension is common.