Mainzer-Saldino syndrome (MSS) or conorenal syndrome (CRS) is a rare autosomal recessive ciliopathy characterized by multiorgan affection, typically presents with a triad of nephronophthisis (NPHP), retinitis pigmentosa (RP), and cone-shaped epiphysis (CSE) with varying degrees of severity. A 20-month-old male is experiencing recurrent pneumonia attacks, an elevated serum creatinine level, proteinuria, and high anion gap partially compensated metabolic acidosis were incidentally discovered during one of his hospitalizations. A biopsy was performed, and the results supported the diagnosis of Alport syndrome. However, a subsequent genetic test suggests the presence of MSS. Aside from NPHP, RP and CSE tested positive. Based on the fact that MSS is not a common cause of end-stage renal disease (ESRD) in pediatrics, physicians should bear in mind genetic testing as a decisive tool. In this context, we highlighted a case of an accidentally discovered impaired renal function from first presentation to final diagnosis, with a valuable comparison with previously published similar cases.

A seven-month-old girl presented with bilateral roving nystagmus, hyperopia, and retinal dystrophy, and was brought to our ophthalmology clinic. Visual-evoked potentials (VEPs) were non-recordable in both the eyes. No other systemic symptoms or abnormalities were observed. Whole exome sequencing (WES) identified a compound heterozygous mutation in the IFT140 gene: c.1990G > A (p. Glu664Lys) and c.2214_2217del (p.Asp738GlufsTer47). The genetic results support a diagnosis of Mainzer-Saldino syndrome (MSS). Importantly, c.2214_2217del is a novel mutation in the IFT140 gene. Although the patient presents with isolated retinal dystrophy, it is crucial to monitor renal function overtime. Taken together, our results reinforce the role of IFT140 in syndromic ciliopathies. This report also highlights the role of combined WES approaches in identifying underlying mutations in infants presenting with isolated retinal dystrophy, considering MSS may present differently over time.

Background: Syndromic ciliopathies have been variably linked to different retinal dystrophies. However, to date, few reports have characterized by means of multimodal imaging the retinal degeneration occurring in Mainzer-Saldino syndrome (MSS).Methods: Two siblings with history of kidney disease and other systemic abnormalities presented at our eye clinic in October 2017 complaining of night blindness and visual loss. They underwent a complete ophthalmologic examination including visual acuity (VA) assessment, optical coherence tomography (OCT) and blue-light autofluorescence (BAF). A screen for inherited retinal dystrophies was performed in this occasion.Results: At baseline, the youngest sister had slightly worse VA (20/30 vs. 20/20-25 Snellen equivalents). On fundoscopy, both siblings had severe thinning of the peripheral retina, attenuation of retinal vessels and widespread accumulation of pigmented deposits. Significant outer retinal atrophy with apparent foveal sparing was appreciable on OCT.During the 3 years of follow-up, vision remained overall stable in both patients whereas minimal progression of outer retinal atrophy was observed by means of OCT. Genetic analysis revealed compound heterozygosity in the IFT172 gene. Based on these findings, a diagnosis of retinitis pigmentosa (RP) associated with MSS was formulated.Conclusions: Our report describes the cases of two siblings affected by retinitis pigmentosa associated with MSS. Although both carrying the same mutations and a severe RP phenotype, the youngest sister had slightly more advanced retinal degeneration highlighting the remarkable variability related to the IFT172 retinopathy.

Ciliopathies are a wide and heterogeneous group of diseases affecting intraflagellar transport. Among them, Mainzer-Saldino syndrome (MSS) shows phalangeal cone-shaped epiphysis, renal disease and retinal involvement. Short stature, cerebellar ataxia and hepatic fibrosis might also be found. IFT140 is the most commonly reported mutation in MSS. We will report on the case of a patient with a clinical diagnosis of Mainzer-Saldino syndrome due to IFT144 dysfunction. This mutation has not been previously related to MSS but it has been found in other ciliopathies and both syndromic and non-syndromic retinitis pigmentosa. At birth our patient showed trigonocephaly, early progressive renal failure requiring transplant, intrahepatic biliary duct dilation, cone-shaped epiphyses, growth retardation and retinitis pigmentosa with mild ophthalmic impairment. The best corrected visual acuity reached 0.15/0.22 LogMAR. The posterior pole showed abnormal macular reflex, mild vascular attenuation in the periphery and diffuse pigmentary changes. Autofluorescence showed bull\'s eye signal increase. Computerized optic tomography assessed the absence of external retinal layers in the extrafoveal macula. In conclusion, IFT144 genetic study may be involved in MSS and thus must be considered for diagnosis. Mild ophthalmic symptomatology despite early onset retinitis pigmentosa in the context of MSS has been found in this case caused by IFT144 mutation.

Ciliopathies represent a wide spectrum of rare diseases with overlapping phenotypes and a high genetic heterogeneity. Among those, IFT140 is implicated in a variety of phenotypes ranging from isolated retinis pigmentosa to more syndromic cases. Using whole-genome sequencing in patients with uncharacterized ciliopathies, we identified a novel recurrent tandem duplication of exon 27-30 (6.7 kb) in IFT140, c.3454-488_4182+2588dup p.(Tyr1152_Thr1394dup), missed by whole-exome sequencing. Pathogenicity of the mutation was assessed on the patients\' skin fibroblasts. Several hundreds of patients with a ciliopathy phenotype were screened and biallelic mutations were identified in 11 families representing 12 pathogenic variants of which seven are novel. Among those unrelated families especially with a Mainzer-Saldino syndrome, eight carried the same tandem duplication (two at the homozygous state and six at the heterozygous state). In conclusion, we demonstrated the implication of structural variations in IFT140-related diseases expanding its mutation spectrum. We also provide evidences for a unique genomic event mediated by an Alu-Alu recombination occurring on a shared haplotype. We confirm that whole-genome sequencing can be instrumental in the ability to detect structural variants for genomic disorders.

OBJECTIVE: Genetic heterogeneity and phenotypic variability are major challenges in familial nephronophthisis and related ciliopathies. To date, mutations in 20 different genes (NPHP1 to -20) have been identified causing either isolated kidney disease or complex multiorgan disorders. In this study, we provide a comprehensive and detailed characterization of 152 children with a special focus on extrarenal organ involvement and the long-term development of ESRD.
METHODS: We established an online-based registry (www.nephreg.de) to assess the clinical course of patients with nephronophthisis and related ciliopathies on a yearly base. Cross-sectional and longitudinal data were collected. Mean observation time was 7.5±6.1 years.
RESULTS: In total, 51% of the children presented with isolated nephronophthisis, whereas the other 49% exhibited related ciliopathies. Monogenetic defects were identified in 97 of 152 patients, 89 affecting NPHP genes. Eight patients carried mutations in other genes related to cystic kidney diseases. A homozygous NPHP1 deletion was, by far, the most frequent genetic defect (n=60). We observed a high prevalence of extrarenal manifestations (23% [14 of 60] for the NPHP1 group and 66% [61 of 92] for children without NPHP1). A homozygous NPHP1 deletion not only led to juvenile nephronophthisis but also was able to present as a predominantly neurologic phenotype. However, irrespective of the initial clinical presentation, the kidney function of all patients carrying NPHP1 mutations declined rapidly between the ages of 8 and 16 years, with ESRD at a mean age of 11.4±2.4 years. In contrast within the non-NPHP1 group, there was no uniform pattern regarding the development of ESRD comprising patients with early onset and others preserving normal kidney function until adulthood.
CONCLUSIONS: Mutations in NPHP genes cause a wide range of ciliopathies with multiorgan involvement and different clinical outcomes.