Pick’s disease was discovered by Arnold Pick in 1892. The meaning of the term “pick’s disease” has changed dramatically over the years. In the past, it was used to describe frontotemporal dementia (FTD) but now it represents a histopathological subtype of FTD. FTD belongs to an even broader pathology called frontotemporal lobe degeneration (FTLD). FTD is any form of dementia in which the frontal and temporal lobes of the brain degenerate.
It is characterized by the presence of intraneuronal inclusions in the form of pick bodies and ballooned cells in the brain called pick cells. These inclusions contain aggregates of abnormal tau protein. Tau protein in PiD is 3-repeat, meaning the Tau protein exists in various isoforms and large amounts of 3-repeat have profound axonal transport defects and locomotor impairments. PiD is a primary tauopathy (deposition of abnormal levels of Tau protein). Healthy tau protein helps in the assembly of microtubules in the neurons. It is coded by the MAPT gene. Six isoforms of tau are coded by this gene. These isoforms are categorized into two types depending upon the number of repeats in them. Three isoforms are 3R while three are 4R. The relative level of these two groups of isoforms can have important implications for neurodegenerative diseases. Tau protein in PiD belongs to the 3R type.
The age of onset of PiD ranges from 40 to 75 years. PiD is more prevalent among men than in women. FTD is divided into clinical subtypes such as behavioral variants called bvFTD and diminished language skills called primary progressive aphasia (PPA). bvFTD presents the most common set of symptoms in PiD. Most cases of PiD have a sporadic origin.
Characteristic symptoms of PiD include:
Caregiving in PiD is particularly difficult due to the inappropriate behavior of patients towards caregivers. PiD patients show stereotypic, sexually inappropriate, and impulsive behavior. PiD patients also suffer from anomia; a condition in which a person has difficulty remembering the names of objects and places. Akinesia and rigidity may occur in the later stages of the disease. Symptoms get worse with advancing stages.
Diagnosis of living PiD patients is difficult because of the lack of specific biomarkers for pick bodies. However, antibodies can be used in the diagnosis of PiD. Cognitive and behavioral tests are currently the best option for diagnosing PiD. Despite all these options, many PiD patients are misdiagnosed. Brain imaging can be used to visualize atrophy. Most patients suffering from PiD have mixed pathology in which other neurodegenerative diseases are also involved. Frontotemporal lobar atrophy is a prominent sign of PiD. Knife-edge-like cortical atrophy can be observed upon gross examination.
No treatment can slow down or reverse the progression of PiD. Different drugs can be used to manage the symptoms and the treatment is highly individualized. Cholinesterase inhibitors are used for the behavioral management of PiD. The drugs being used to manage symptoms of PiD are intended for the symptomatic treatment of other disorders such as Alzheimer’s disease (AD). Much work needs to be done to understand the pathophysiology of PiD to develop disease-modifying treatments.