HUT (Hutterite)

Inheritance: autosomal recessive
Genes: unknown

Cerebellooculorenal syndrome 2
Joubert syndrome-related disorder
JSRD
JBS

Developmental and growth delay
Ataxia
Hypotonia
Ocular abnormalities
Polycystic kidney disease
Brain malfomations
Molar tooth sign
Encephalocele
Breathing problems
Sleep apnea
Polydactyly

Joubert Syndrome (JSRD)

Clinical Characteristics

General description (for patients):  

This is a complex disorder with uncertain classification beyond that of belonging to a general group of diseases that have malformations of the brain, eye, and kidneys.  The diagnosis may be made at birth when abnormal formation of the brain is evident while in others it is evident when growth and mental retardation are noted. Kidney disease secondary to cyst formation can also present early.  Sleep disorders with interrupted breathing are common, as are vision problems secondary to abnormal retinal functioning.

Medical description:  

Joubert syndrome is a clinically and genetically heterogeneous group of disorders involving brain malformations, hypotonia, developmental delay, oculomotor apraxia and ataxia.  When combined with polydactyly, retinal anomalies, hepatic fibrosis and cystic kidney disease, it is more commonly called Joubert syndrome-related disease and overlaps with the Meckle syndrome.  Encephaloceles, vermal hypoplasia in the cerebellum, ocular colobomas, pigmentary retinopathy, nystagmus, sleep apnea, self mutilation, and a “molar tooth sign” on CNS MRIs are variably present.  Fluid collection in the posterior fossa resembling Dandy-Walker malformation may also be present. Facial dysmorphology with a high forehead, flat midface, hypertelorism, open mouth, low-set ears, and other features are often noted.

Genetics:

Numerous mutations on multiple chromosomes have been identified in what must be an incompletely classified collection of what is often called Joubert syndrome-related disorders (JSRD).  Another possibly novel variation has been described among 10 Hutterite patients in Canada.  All parents were related to at least one other parent but not all matings were documented to be consanguineous.  All known loci for JSRD were excluded by genotyping and the causative mutation remains unknown suggesting this may be a new autosomal recessive disorder.

Treatment:

General care.

Prognosis:  

Highly variable. Patients may be stillborn, live for a few days, or live for several decades.  All are severely disabled.

Ancillary treatments and support:

As required for acute problems and long term supportive care.

Specialists and specialty centers:

Neurologist, Nephrologist, Ophthalmologist, Pediatrician.

References:

Boycott, K.M., Parboosingh, J.S., Scott, J.N., McLeod, D.R., Greenberg, C.R., Fujiwara, T.M., Mah, J.K., Midgley, J., Wade, A., Bernier, F.P., Chodirker, B.N., Bunge, M., and Innes, A.M.:  Meckel syndrome in the Hutterite population is actually a Joubert-related cerebello-oculo-renal syndrome.  Am. J. Med. Genet. 143A: 11715-1725, 2007. PubMed ID: 17603801

Blair, I.P., Gibson, R.R., Bennett, C.L., and Chance, P.F.:  Search for genes involved in Joubert syndrome: evidence that one or more major loci are yet to be identified and exclusion of candidate genes EN1, EN2, FGF8, and BARHL1.  Am. J. Med. Genet. 107: 190-196, 2002.  PubMed ID: 11807898

Cantani, A., Lucenti, P., Ronzani, G.A., and Santoro, C.:  Joubert syndrome: review of the fifty-three cases so far published.  Ann. Genet. 33: 96-98, 1990.  PubMed ID: 2241092


Resources:

Joubert Syndrome Foundation