Vermian hypoplasia and arrested cerebral myelination in two sisters: variant of Joubert's syndrome or a new syndrome?

Two adult sisters have vermian hypoplasia, ataxia, nystagmus, pontine divergence insufficiency, and mild to moderate intellectual disability, with an arrest of cerebral myelination resembling the pattern of a 4-month-old infant. Other abnormalities include high myopia, optic nerve hypoplasia, decreased bone density, hypoplasia of the secondary teeth, and amenorrhea. We did not find matching patients described in the literature. The sisters could represent a variant of one of the described syndromes of the cerebellocerebro-oculorenal spectrum, such as a variant of Joubert's syndrome, or a disorder sui generis within the spectrum.