Delusional parasitosis with hyperthyroidism in an elderly woman: a case report

Delusional parasitosis is a rare, monosymptomatic psychosis involving a delusion of being infested with parasites. It is commonly observed among female patients over the age of 50. It is classified as a ‘delusional disorder’ according to the 10^th revision of the International Classification of Diseases and as a ‘delusional disorder - somatic type’ according to the Diagnostic and Statistical Manual, Fourth Edition. Delusional parasitosis was reported to be associated with physical disorders such as hypoparathyroidism, Huntington’s chorea and Alzheimer’s disease, among others. Other than vitamin deficiencies however, a causal relationship has not to date been identified. We present this case due to the rarity of Turkish patients with this condition, its duration of follow-up, and its temporal pattern of symptoms paralleling thyroid function tests.

Our patient was a 70-year-old white Anatolian Turkish woman with primary school education who had been living alone for the past five years. She presented to our psychiatry department complaining of ‘feeling large worms moving in her body’. The complaints started after she was diagnosed with hyperthyroidism, increased when she did not use her thyroid medications and remitted when she was compliant with treatment. She was treated with pimozide 2mg/day for 20 months and followed-up without any antipsychotic treatment for an additional nine months. At her last examination, she was euthyroid, not receiving antipsychotics and was not having any delusions.

Although endocrine disorders, including hyperthyroidism, are listed among the etiological factors contributing to secondary delusional parasitosis, as far as we are aware this is the first case demonstrating a temporal pattern of thyroid hyperfunction and delusions through a protracted period of follow-up. It may be that the treatment of delusional parasitosis depends on clarifying the etiology and that atypical antipsychotics may help in the management of primary delusional parasitosis. Further studies on the relationship between thyroid hormones and dopaminergic neurotransmission may be warranted.