Lesser Known and Rare Types of Dementia

Last Updated: July 30, 2020


Alzheimer’s disease is by far the most common illness associated with dementia, but there are related diseases that affect hundreds of thousands of Americans. Sometimes dementia is an early symptom of these diseases, and other times it occurs as the disease progresses and gets worse. Alzheimer’s disease, Lewy body dementia, frontotemporal dementia, and vascular dementia are the four most common, but lesser-known dementia diseases can be caused by head trauma, HIV, genetics, alcoholism, and more.

If your loved one is showing symptoms of dementia, it’s possible one of these rarer illnesses may be the cause. Getting diagnosed is vital, because knowing the type determines treatment, and while most dementias cannot be cured, symptoms can be managed so a person’s quality of life remains high. On this page, we will list and explain rarer forms of dementia.

 Did You Know? More than one out of 10 people with dementia has mixed dementia, meaning multiple types of these diseases occurring in the brain at once.


Atypical Alzheimer’s Disease

Roughly one in 20 people with Alzheimer’s have an atypical type of the disease. This means the disease is caused by the same types of amyloid beta plaques and tau tangles that cause Alzheimer’s, but in a different region of the brain.

Frontal Variant Alzheimer’s Disease

Frontal variant Alzheimer’s disease (fvAD) attacks the front of the brain during the earliest stages, whereas typical Alzheimer’s usually takes years to get to the frontal lobes. The symptoms are the same as Alzheimer’s disease, including memory and behavior problems. FvAD only impacts about one in 50 people with Alzheimer’s, and is difficult to diagnose. Because it affects a different part of the brain, it’s unknown whether the medications that help relieve symptoms of most people with Alzheimer’s (like cholinesterase inhibitors and memantine) are effective.

Posterior Cortical Atrophy

Posterior Cortical Atrophy also is caused by plaques and tangles, but in the back region of the brain called the visual cortex. Symptoms come on earlier, usually in a person’s 50s. Because that part of the brain processes information from our eyes, the first indications of PCA are usually problems with vision. Difficulty understanding photographs, knowing the faces and objects in a picture, is one early sign that leads to a diagnosis of PCA. Someone with PCA will often take longer to develop memory and behavior problems typically associated with Alzheimer’s, but will lose the ability to read and write. Using smart phones and computers also becomes a problem and driving quickly becomes unsafe.


Parkinson’s Disease Related Dementia

Parkinson’s disease is a progressive disease that affects many middle-aged and older adults, and sometimes leads to dementia. . The most common symptoms of Parkinson’s are related to motor skills: tremors, stiffness, slowed movement, and impaired balance. According to the Alzheimer’s Association, between 50 and 80 percent of people with Parkinson’s develop Parkinson’s disease with dementia (PDD). Symptoms may include memory loss and trouble finding words, but a difference between PDD and Alzheimer’s is that PDD more strongly affects mood, causing depression and anxiety at a higher rate.

Per the National Parkinson Foundation, if dementia symptoms begin at least a year after motor issues develop, a diagnosis of Parkinson’s dementia is warranted. Sometimes dementia symptoms are considered part of the disease, but sometimes a separate diagnosis — for instance, of Alzheimer’s disease — may be made. Please note, there is also a great deal of overlap in the symptoms of Parkinson’s disease and Lewy Body dementia. Physicians use a variety of techniques and tests to make a correct diagnosis.

For more on Parkinson’s disease with dementia, click here.


Huntington’s Disease Related Dementia

Huntington’s disease (HD) is genetic: If an individual’s parent has the defective gene and he or she inherits it, HD is unfortunately inevitable. (Genetic testing can determine if someone will develop Huntington’s.) This disease generally begins earlier in life, between ages 30 and 50, and is characterized by mood swings, lack of coordination, impaired judgment, muscle stiffness (called “dystonia”) and involuntary movements (called “chorea”). People with Huntington’s develop dementia symptoms as the disease progresses. Compared to Alzheimer’s disease, however, people with dementia from Huntington’s have fewer memory problems, but more problems with language, communication and decision-making. Unlike other dementias, they will be aware of their illness, remaining on the same mental level, as their ability to move and talk gets worse. This makes sympathy and understanding from loved ones especially important.

For more on Huntington’s disease, click here.


Normal Pressure Hydrocephalus

A major difference between normal pressure hydrocephalus (NPH) and other dementias on this page, including Alzheimer’s, is that NPH can be cured, or at least dramatically improved, with surgery. NPH is caused by excessive spinal fluid in the brain. The buildup of pressure impares thinking like with other dementias (trouble focusing, loss of short-term memory) and makes walking hard for people (who say it feels like their feet are stuck to the ground). Trouble with bladder control might also occur. Someone with these symptoms may be diagnosed with normal pressure hydrocephalus. Fortunately, when surgeons insert a thin tube called a “shunt” into the brain, the excess fluid can be drained and symptoms improve quickly.

For more on normal pressure hydrocephalus, click here.


Creutzfeldt-Jakob Disease

Creutzfeldt-Jakob disease (CJD) develops spontaneously and gets worse much faster than other dementias like Alzheimer’s disease. Most individuals diagnosed with CJD die within a year, after the rapid destruction of brain cells causes memory problems like other dementias, as well as mood swings, involuntary muscle movements, difficulty seeing and difficulty walking. CJD is the most common of a group of rare dementia types called spongiform encephalopathy or prion diseases, the result of abnormal proteins in the brain called prions. Once present in the brain, prions “infect” healthy proteins, creating new prions.

There are three types of CJD:

– Sporadic Creutzfeldt-Jakob disease: Appears in the brain for no known reason. More than 80 percent of CJD cases are sporadic.
– Familial Creutzfeldt-Jakob disease: Inherited from parents who carry a specific gene. This type develops at a much younger age, often between 20 and 40.
– Acquired Creutzfeldt-Jakob disease: Comes from exposure to tissue and fluids from the brain and spine of someone with CJD, or eating meat from cattle infected with the disease. These cases are incredibly rare.


Dementia in Persons with HIV/AIDS

Dementia can occur when the HIV virus attacks one’s nervous system and causes damage to the brain cells. When symptoms including memory loss, poor judgment, confusion, mood swings, difficulty with coordination, and trouble learning new things are severe enough to interfere with daily life, a diagnosis of HIV dementia may be given. These symptoms may be reversible with treatment, and certain HIV drug (antiretroviral) therapies have been shown to make dementia less likely. A milder form of cognitive impairment (thinking problems) in people with HIV, called HIV Associated Neurocognitive Disorder or HAND, can still affect the brain.


Dementia From Traumatic Brain Injury

Trauma (physical injury) to the head, most often from falls or car accidents, can lead to cognitive and memory problems similar to dementia. Symptoms depend upon the severity of the trauma and what part of the brain was affected. Potential symptoms of a head injury include dizziness and loss of balance (vertigo), headache, blurred vision, memory and cognitive (thinking) problems, sleeping problems, restlessness, irritability, apathy, depression, emotional outbursts, impulsiveness, and anxiety. Milder injuries may include symptoms like difficulty concentrating, paying attention, and attending to so-called “executive functions” (planning, organizing, abstract reasoning, problem solving, and making judgments). If the injury is severe, the person may lose many higher-level mental skills, like the ability to retain past memories or form new ones.Treatment for traumatic brain injuries commonly includes medications, counseling, and/or occupational therapy.
Also notable here is that repeated mild traumatic brain injuries can cause a disease called chronic traumatic encephalopathy (CTE), whose symptoms are the same as those listed above. CTE has been shown in particular to affect football players and military veterans. (Click here for more on CTE.)


Wernicke-Korsakoff Syndrome (Including Alcohol-Related Dementia)

Wernicke-Korsakoff Syndrome (WKS) is caused by a lack of the vitamin B1, also known as thiamine, which helps the brain turn sugar into energy. Deficiency in this vitamin is sometimes related to alcoholism, but it is also seen in a number of other conditions including AIDS, cancer, malnutrition and eating disorders. The symptoms of Wernicke-Korsakoff Syndrome include memory loss and cognitive decline as well as confabulation (making up stories), vision changes, and loss of muscle coordination. The syndrome often, but not always, begins with a medical incident called Wernicke encephalopathy, where lack of thiamine causes sudden confusion, stumbling, and rapid eye movements. These episodes can be fatal. When WKS is caught in the early stages, however, a person can make a significant recovery.



Leukodystrophy is a group of genetic diseases that affect children, although there are also cases of adult-onset leukodystrophy. These diseases result from a problem with myelin, the covering for nerves that makes up the white matter in the brain. Signs and symptoms vary with the particular type of leukodystrophy, but most types are characterized by gradual decline of various abilities, such as limited speech and movement in a child who previously seemed well. The treatment and outcome for the disease depend on the type of leukodystrophy.