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Joubert syndrome (JS) is rare recessive disorders characterized by the combination of hypoplasia/aplasia of the cerebellar vermis, thickened and elongated superior cerebellar peduncles, and a deep interpeduncular fossa which is defined by neuroimaging and is termed the 'molar tooth sign'. JS is genetically highly heterogeneous, with at least 29 disease genes being involved. To further understand the genetic causes of JS, we performed whole-exome sequencing in 24 newly recruited JS families. Together with six previously reported families, we identified causative mutations in 25 out of 30 (24 + 6) families (83.3%). We identified eight mutated genes in 27 (21 + 6) Japanese families, TMEM67 (7/27, 25.9%) and CEP290 (6/27, 22.2%) were the most commonly mutated. Interestingly, 9 of 12 CEP290 disease alleles were c.6012-12T>A (75.0%), an allele that has not been reported in non-Japanese populations. Therefore c.6012-12T>A is a common allele in the Japanese population. Importantly, one Japanese and one Omani families carried compound biallelic mutations in two distinct genes (TMEM67/RPGRIP1L and TMEM138/BBS1, respectively). BBS1 is the causative gene in Bardet-Biedl syndrome. These concomitant mutations led to severe and/or complex clinical features in the patients, suggesting combined effects of different mutant genes., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

A female case of developmental arrest, early-onset seizures, retinal pigmentary degeneration, progressive central nervous symptoms and peripheral neuropathy, associated with progressive renal dysfunction, anemia and nephrotic syndrome, was presented. Her epileptic syndrome was possibly an early myoclonic encephalopathy, though neonatal seizures were not evident. Serial cranial MRIs showed progressive brain atrophy and a white matter change. Neuropathological examination revealed a neurodegenerative disease mainly involving the white matter with olivopontocerebellar degeneration. She also had the nephronophthisis-medullary cystic disease complex and an early stage of focal segmental glomerulosclerosis. Her grandaunts had renal diseases, one of whom died of renal failure in adolescence, and her father showed cerebellar symptoms since the middle age. All possible metabolic studies were negative. This case is similar to Senior-Loken syndrome, but distinct in terms of the severe and progressive neurological symptoms, suggestive of a new malignant syndrome with some inherent metabolic derangement affecting both the nervous system and the kidneys.