Mutations in B9D1 and MKS1 cause mild Joubert syndrome: expanding the genetic overlap with the lethal ciliopathy Meckel syndrome

Table 1 Phenotypic comparison of the four patients presented here with JS clinical subgroups

	Present cases				JS clinical subgroups (as in ref 1)
	COR340 ( MKS1)	COR413 ( MKS1)	COR363 ( B9D1)	COR346 ( B9D1)	Pure	With retina	With kidney	With retina & kidney	With liver	OFD-VI
CNS:
- hypotonia/ataxia	+	+	+	+	+	+	+	+	+	+
- breathing abn.	-	-	-	-	±	±	±	±	±	±
- develop. delay	+	+	+	+	+	+	+	+	+	+
- ID	+	+	+	-	±	+	+	+	+	±
- oculomotor abn.*	+	+	+	+	±	±	±	±	±	±
Ocular:
- retinopathy	+	-	-	-	-	+	-	+	-	-
- coloboma	-	-	-	-	±	rare	rare	rare	±	rare
Renal:	-	-	-	-	-	-	+	+	±	rare
Hepatic:	-	-	-	-	-	-	-	rare	+	-
Other features:
- polydactyly	-	-	-	-	±	rare	rare	rare	rare	±
- orofacial features	-	-	-	-	-	-	-	-	-	±
- dysmorphisms	+	-	+	+	±	±	±	±	±	±
Neuroimaging:
- MTS	+	+	+	+	+	+	+	+	+	+
- other CNS defects**	-	-	-	-	rare	rare	rare	rare	rare	±

Legend: For the six JS subgroups, the meaning of symbols is as follows: “+”: mandatory feature; “±”: feature that could be part of the phenotype but is not mandatory; “rare”: feature that was only rarely described in the subgroup; “-“: never described to date. *mainly oculomotor apraxia and/or nistagmus; **mostly including corpus callosum hypoplasia, encephalocele, neuronal migration defects (e.g. polymicrogyria), hypothalamic hamartoma (in OFD-VI).
Abbreviations: abn abnormalities, CNS central nervous system, develop developmental, ID intellectual disability of variable severity, MTS molar tooth sign.

ISSN: 1750-1172