HD is an autosomal, dominantly inherited, neurodegenerative disorder which can present with cognitive, motor and behavioural symptoms. Recent studies suggest that obsessive compulsive disorder (OCD) symptoms, although not common, may precede or coincide with symptoms in patients with HD. We present a case of an adolescent boy presenting with symptoms of OCD, for 4 months duration, in background of three years diagnosis of HD.

A 15-year-old boy from South India, presented with recurrent, intrusive thoughts of sexual content, consistent with obsessions and some instances of compulsions in the form of avoiding to do deviant sexual act like fetishism, and having excessive worries about an act he had done earlier for 3 months duration (supported by high scores on Yale-Brown Obsessive Compulsive Scale; Y-BOCS). Patient had normal birth and development and had no past history of psychiatry disorder, however there was family history of HD in multiple first and second-degree relatives. He was on treatment for movement symptoms of HD, diagnosed 3 years back and was on Tetrabenazine for 2 years. Initial psychiatric assessment found the symptoms to be consistent with OCD due to Huntington's disease, according to Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). The patient was admitted to the mental health unit and was started on Fluoxetine, titrated to a dose of 20mg daily for symptoms of OCD.

Subject showed an excellent response to fluoxetine with complete remission of OCD symptoms within 4 weeks of treatment. The relationship between OCD and HD has been little-investigated, despite the fact that both diseases are associated with striatal dysfunction and that the number of case reports of obsessive-compulsive symptoms either preceding the clinical onset of HD or during later stages of the disease is increasing. For example, Dewhurst et al. reported “obsessional features” in 7 of 102 patients at onset of HD.

Firm conclusions to explain this result cannot be drawn. However, a hypothetical involvement of the serotonergic system, suggested by the excess of OCD, seems supported by the response of said subject to fluoxetine. It may be worth further exploring the value of the psychiatric picture in selecting the appropriate treatment for at least some cases of HD. Anecdotal evidence suggest that SSRIs alone or in combination with atypical antipsychotics like olanzapine may be useful for these patients. However, these hypotheses need further testing.