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Editor—Van Royen-Kerkhof et al 1 reported two boys with Gaucher disease type 1 and Joubert syndrome (JS). Their case 1 had, in addition to mental retardation, choreoretinal colobomas, cerebellar vermis agenesis, and abnormal breathing, agenesis of the corpus callosum, hydrocephalus (no further details given), and generalised seizures. Their case 2 had prenatal hydrocephalus and “fulfilled the diagnostic criteria for JS”. Information about brain anatomy and retinal findings in case 2 is lacking.
We question the diagnosis of JS in these two patients. The authors cite a 1992 paper2 but fail to reference 1997 and 1998 publications that better define the phenotype and characteristic neuroimaging of JS.3-5 In these most recent publications, the “molar tooth sign” is defined as well as a number of distinct posterior fossa abnormalities not discussed by Van Royen-Kerkhofet al.1 This is a significant omission because vermis hypoplasia alone is not pathognomonic for JS and can be seen in mimicking conditions that produce congenital oculomotor apraxia and ataxia.6 7 In addition, to the best of our knowledge, corpus callosum agenesis, hydrocephalus, and generalised seizures are not associated with JS, as these features were not encountered in our combined series of more than 60 JS patients. At a 1998 Child Neurology Society symposium on JS sponsored by the National Institutes of Health, there was general agreement about the common and occasional abnormalities in JS that did not include the clinical or radiological features reported by Van Royen-Kerkhofet al 1 in the two children with Gaucher disease type 1. The proceedings of the symposium will appear in the Journal of Child Neurology in the autumn of 1999.
This letter was shown to Drs van Royen-Kerkhof et al, who reply as follows.
We thank Drs Boltshauser and Maria for their comments on our Letter to the Editor.1 The diagnosis of Joubert syndrome (JS) in case 1 was made 17 years ago on clinical grounds including a CT scan; MRI scanning was not yet available in those days. We were not aware of the paper of 1997.3 The other papers the authors mention had not been published at the time our paper was submitted. As a consequence the “molar tooth sign” was not discussed. We think that corpus callosum agenesis and hydrocephalus are rather non-specific developmental defects whose presence or absence do not argue significantly for or against JS. In our opinion the presence in both cases 1 and 4 of episodic hyperpnoea/apnoea remains an argument in favour of JS.