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Table 1 Classification of Joubert syndrome and related disorders based on associated clinical features

From: Joubert Syndrome and related disorders

Clinical subtypes Mandatory features Preferentially associated features* Previously used nosology Major gene(s)**
Pure Joubert syndrome (JS) MTS   JS Mutations in many genes
    JS type A  
JS with ocular defect (JS-O) MTS    
  Retinal dystrophy (including LCA)   JS type B AHI1
JS with renal defect (JS-R) MTS    NPHP1
  NPH    RPGRIP1L
  MTS   Cerebellooculorenal s.  
JS with oculorenal defects (JS-OR) Retinal dystrophy (often LCA) (CHF reported in few cases) SLS plus MTS CEP290
  NPH   JS type B  
    Dekaban-Arima s.  
JS with hepatic defect (JS-H) MTS Colobomas COACH s. TMEM67
  CHF NPH Gentile s.  
JS with orofaciodigital defects (JS-OFD) MTS   Váradi-Papp s.  
  Lobulated/bifid tongue (incl. hamartomas) Cleft lip/palate Orofaciodigital VI s. TMEM216 (2 patients only)
  Polydactyly    
  1. *Features not correlated with a specific clinical subtype include: postaxial polydactyly; encephalocele and other central nervous system malformations; neuronal migration defects (e.g. polymicrogyria); Hirschsprung's disease; congenital heart defects; laterality defects.
  2. **Besides the major genes listed here, other genes have been occasionally associated with clinical subtypes. Mutations in the CC2D2A gene give rise to a wide phenotypic spectrum [13, 73, 85]. For INPP5E, ARL13B and OFD1 genes, only few mutated patients have been described to date [6870]. Abbreviations: CHF: congenital hepatic fibrosis; incl.: including; JS: Joubert syndrome; LCA: Leber congenital amaurosis; MTS: molar tooth sign; NPH: nephronophthisis; s.: syndrome; SLS: Senior-Löken syndrome.