Purpose This study aimed to delineate the genetic basis of congenital ocular motor apraxia (COMA) in patients not otherwise classifiable. Methods We compiled clinical and neuroimaging data of individuals from six unrelated families with distinct clinical features of COMA who do not share common diagnostic characteristics of Joubert syndrome or other known genetic conditions associated with COMA. We used exome sequencing to identify pathogenic variants and functional studies in patient-derived fibroblasts. Results In 15 individuals, we detected familial as well as de novo heterozygous truncating causative variants in the Suppressor of Fused (SUFU) gene, a negative regulator of the Hedgehog (HH) signaling pathway. Functional studies showed no differences in cilia occurrence, morphology, or localization of ciliary proteins, such as smoothened. However, analysis of expression of HH signaling target genes detected a significant increase in the general signaling activity in COMA patient–derived fibroblasts compared with control cells. We observed higher basal HH signaling activity resulting in increased basal expression levels of GLI1, GLI2, GLI3, and Patched1. Neuroimaging revealed subtle cerebellar changes, but no full-blown molar tooth sign. Conclusion Taken together, our data imply that the clinical phenotype associated with heterozygous truncating germline variants in SUFU is a forme fruste of Joubert syndrome.

BackgroundAcute tubulointerstitial nephritis (TIN) is a significant cause of acute renal failure in paediatric and adult patients. There are no large paediatric series focusing on the aetiology, treatment and courses of acute TIN.Patients, design and settingWe collected retrospective clinical data from paediatric patients with acute biopsy-proven TIN by means of an online survey. Members of four professional societies were invited to participate.ResultsThirty-nine physicians from 18 countries responded. 171 patients with acute TIN were included (54% female, median age 12 years). The most frequent causes were tubulointerstitial nephritis and uveitis syndrome in 31% and drug-induced TIN in 30% (the majority of these caused by non-steroidal anti-inflammatory drugs). In 28% of patients, no initiating noxae were identified (idiopathic TIN). Median estimated glomerular filtration rate (eGFR) rose significantly from 31 at time of renal biopsy to 86 mL/min/1.73 m2 3–6 months later (p<0.001). After 3–6 months, eGFR normalised in 41% of patients (eGFR ≥90 mL/min/1.73 m2), with only 3% having severe or end-stage impairment of renal function (<30 mL/min/1.73 m2). 80% of patients received corticosteroid therapy. Median eGFR after 3–6 months did not differ between steroid-treated and steroid-untreated patients. Other immunosuppressants were used in 18% (n=31) of patients, 21 of whom received mycophenolate mofetil.ConclusionsDespite different aetiologies, acute paediatric TIN had a favourable outcome overall with 88% of patients showing no or mild impairment of eGFR after 3–6 months. Prospective randomised controlled trials are needed to evaluate the efficacy of glucocorticoid treatment in paediatric patients with acute TIN.

ZUSAMMENFASSUNGDie akute tubulointerstitiellen Nephritis (TIN) stellt eine wichtige Ursache des akuten Nierenversagens bei Erwachsenen und Kindern dar. Auslöser der TIN sind eine Vielzahl von Medikamenten, systemische Erkrankungen und Infektionen. Weiterhin existieren idiopathische Fälle ohne identifizierbare Ursache. Eine Sonderform der Erkrankung ist die tubulointerstitielle Nephritis mit Uveitis (TINU), die bei Kindern und Jugendlichen häufiger als bei Erwachsenen vorkommt. Klinische Symptomatik und Laborbefunde der TIN sind häufig unspezifisch, sodass die definitive Diagnose nur bioptisch gesichert werden kann. Die Entfernung der auslösenden Substanz bzw. die Behandlung der Grunderkrankung sind essenziell für die Therapie der TIN. Der Nutzen der Glukokortikoidtherapie wurde bisher nicht durch randomisierte, kontrollierte Studien belegt.