Progressive spinocerebellar degeneration "plus" associated with Langerhans cell histiocytosis: a new paraneoplastic syndrome?

Langerhans cell histiocytosis (LCH), formerly known as histiocytosis-X, manifests by granulomatous lesions consisting of mixed histiocytic and eosinophilic cells. The hallmark of LCH invasion into the CNS is diabetes insipidus, reflecting local infiltration of Langerhans cells into the posterior pituitary or hypothalumus. In five patients who had early onset LCH with no evidence of direct invasion into the CNS, slowly progressive spinocerebellar degeneration accompanied in some by pseudobulbar palsy and intellectual decline was seen. Neurological impairment started 2.5 to seven years after the detection of LCH. No correlation was found between the clinical syndrome and location of LCH or its mode of treatment. An extensive search for metabolic, toxic, neoplastic, and hereditary aetiologies for progressive cerebellar degeneration was negative. It seems that the clinical entity described here may be considered a new paraneoplastic syndrome related to LCH. It may be induced by the eosinophil derived neurotoxin, which was shown to cause damage to Purkinje cells and pyramidal neurons.