A group of disorders with disparate symptomatology, including congenital 
cerebellar ataxia, retinal blindness, liver fibrosis, polycystic kidney disease, 
and polydactyly, have recently been united under a single disease mechanism 
called 'ciliopathies'. The ciliopathies are due to defects of the cellular 
antenna known as the primary cilium, a microtubule-based extension of cellular 
membranes found in nearly all cell types. Key among these ciliopathies is 
Joubert syndrome, displaying ataxia, oculomotor apraxia, and mental retardation* 
with a pathognomonic 'molar tooth sign' on brain magnetic resonance imaging. The 
importance of ciliary function in neuronal development has been appreciated only 
in the last decade with the classification of Joubert syndrome as a ciliopathy. 
This, together with the identification of many of the clinical features of 
ciliopathies in individuals with Joubert syndrome and the localization of 
Joubert syndrome's causative gene products at or near the primary cilium, have 
defined a new class of neurological disease. Cilia are involved in diverse 
cellular processes including protein trafficking, photoreception, embryonic axis 
patterning, and cell cycle regulation. Ciliary dysfunction can affect a single 
tissue or manifest as multi-organ involvement. Ciliary defects have been 
described in retinopathies such as retinitis pigmentosa and Leber congenital 
amaurosis (defects in photoreceptor ciliary protein complexes), renal syndromes 
with nephronophthisis and cystic dysplastic kidneys, and liver conditions such 
as fibrosis and biliary cirrhosis. Recognizing the diverse presentations of the 
ciliopathies and screening strategies following diagnosis is an important part 
of the treatment plan of children with cilia-related disorders.