Dementia with Lewy bodies presenting as psychotic depression

To the Editor

The core features of dementia with Lewy bodies (DLB) are fluctuating cognitive impairment, recurrent visual hallucinations and parkinsonism (Weisman and McKeith, 2007). We describe the unusual case of a 92-year-old man who presented with a classical phenotype of psychotic depression, treatment of which ‘unmasked’ DLB.

A.B. had no prior psychiatric history. Current medical conditions were hypertension and benign prostatic hypertrophy. He presented with a 6-month history of severe major depressive disorder with associated delusions of guilt. At initial assessment, there was no history of cognitive impairment, and he scored 30/30 on the Mini-Mental State Exam (MMSE) (Folstein et al., 1975). There was no history or signs of parkinsonism. Relevant bloodwork was unremarkable. Magnetic resonance (MR) scan of the brain showed age-related generalized atrophy and mild-moderate white matter changes consistent with chronic microangiopathic disease.

He was diagnosed with psychotic depression and treated with a combination of sertraline and olanzapine (Meyers et al., 2009). The initial starting dose of 2.5 mg/day of olanzapine was associated with development of mild hand tremor. The patient elected to stop the olanzapine, but continued sertraline. Upon admission to hospital because of worsening depression, olanzapine was re-started at 2.5 mg/day and increased to 5 mg/day after 1 week. The re-introduction of olanzapine was associated with worsening tremor, weakness of his legs, impaired mobility and shuffling gait and orthostatic hypotension. In addition, he experienced vivid dreams, visual hallucinations and cognitive impairment (MMSE score 23/30). Depression and delusions persisted.

Given the cognitive dysfunction, hallucinations, parkinsonism and extreme sensitivity to antipsychotic medication, DLB was suspected. As such, antipsychotic medication was discontinued and donepezil 5 mg/day started. Within 1 week, he showed dramatic improvement in both depression and parkinsonism. Both the delusion of guilt and hallucinations remitted. Four weeks later, there was full remission of depressive symptoms and the psychosis had not recurred; however, mild parkinsonism persisted; MMSE score was 29/30, losing one point on recall. As the diagnosis was in keeping with probable DLB, and not psychotic depression, sertraline was withdrawn. Five months later, symptoms of depression and psychosis remained in remission.

This case is a reminder that first-onset psychiatric symptoms in ‘very old’ patients are frequently from an organic cerebral disease. Even though this patient presented with the classical phenotype of psychotic depression, treatment with antipsychotic medication ‘unmasked’ probable DLB. Without vigilance to this possibility, the patient may have undergone electroconvulsive therapy as treatment for ‘pharmacotherapy-intolerant’ psychotic depression, with potentially adverse consequences for his cognitive function.