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 …