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In February 1995, Fukuzawa et al described a woman with Erdheim-Chester disease, a rare histiocytic disorder characterised by lipid laden cells infiltrating long bones, who presented with ataxia and diabetes insipidus.1 They thought that this was the first reported case of Erdheim-Chester disease showing cerebellar symptoms and deep cerebellar lesions on MRI. We recently encountered a similar case, but on reviewing the literature we found that a few cases with ataxia and neurological signs had been reported previously. Erdheim and Chester’s first case was thought to have had multiple sclerosis for seven years because of ataxia and ocular signs.2 Subsequently a case was described in the German language by Kujat et al: a 62 year old man who presented with ataxia and bulbar symptoms.3 Brain MRI showed multiple brain stem, diencephalon, and cerebellar lesions. Another case was described by Smith et al: a 58 year old man with brain stem signs had a biopsy taken from the tibia which showed the characteristic lipid laden cells, and MRI of the brain showed multiple lesions.4
So, by contrast with the recognised pattern of skeletal involvement in Erdheim-Chester disease, the involvement of the CNS has variable presentation.
We appreciate the comments made by Bohlega. We agree that Erdheim-Chester disease can show variable CNS involvement,1-1-1-3 and we also suspect that the involvement of the CNS may be relatively common during the entire clinical course of the disease. However, we had not found the case report in German by Kujat et al 1-4 when we submitted our case report. In our article, we described a 59 year old woman with ECD who showed a four year clinical course of slowly progressive cerebellar symptoms, the clinical features of which suggested cerebellar degeneration and were different from those of previously reported cases of Erdheim-Chester disease showing ataxia.1-1-1-4 The symptoms of diabetes inspidus had disappeared spontaneously when we first saw her, although they reappeared three years later. There was no definitive abnormality on CT, whereas MRI showed abnormal hyperintensity on T2 weighted studies in both dentate nuclear regions. Conversely, the brain MRIs of the previously reported patients with ECD who showed neurological signs disclosed multiple enhanced lesions in the CNS.1-2-1-4 We recently found another case report of a slowly progressive cerebellar syndrome associated with Erdheim-Chester disease, a 69 year old man presented with a one year history of progressive gait ataxia, dysarthria, dysphagia, fatigue, and weight loss.1-5 Unlike our patient, however, his brain MRI disclosed multiple white matter enhanced lesions in both cerebral hemispheres, pons, medulla, and brachium pontis. Furthermore, some cases with another form of histiocytosis—multifocal eosinophilic granuloma (MEG)—were reported to have presented as progressive cerebellar syndrome,1-6-1-8 and we previously reported a case with MEG showing progressive cerebellar and brainstem symptoms and multiple enhanced lesions on MRI.1-9 Therefore, these enhanced lesions on MRI may be a common finding of CNS infiltration of histiocytes. From the view of neuroimaging, our patient with ECD presented in this Journal is unique, although we could not clarify whether the MRI appearances were due to histiocytic infiltration. However, Erdheim-Chester disease should be included in the differential diagnosis of patients with otherwise unexplained slowly progressive cerebellar symptoms, and skeletal surveys are also indicated for these patients.
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