Cerebellar involvement in Langerhans' cell histiocytosis: a progressive neuropsychiatric disease.

We describe a 21-year-old patient who was being followed since the age of 3(1/2) years for Langerhans' cell histiocytosis. Although previously a bright and gifted student, the patient presented at age 16(1/2) with new-onset cerebellar neurologic signs, obsessive-compulsive disorder, and dementia. Findings on magnetic resonance imaging study of the brain were normal, but brain single photon emission computed tomography with technetium 99m ethylene cysteinate dimer showed markedly decreased cerebellar perfusion. This case is unique for the wide extent of the central nervous system involvement in Langerhans' cell histiocytosis, which has not been reported previously. Although obsessive-compulsive disorder has also been associated with several other cerebellar disorders, it is still unknown whether the cerebellum plays a role in its development. We suggest that in some cases, brain single photon emission computed tomography may be superior to magnetic resonance imaging for demonstrating cerebellar disorder in Langerhans' cell histiocytosis.