Sufferer, Clare Scott, 76, from Broomfield, Herne Bay, was diagnosed in 2007 and her condition has rapidly deteriorated.
PSP, which has no known cause or cure, affects the trunk of the body and Mrs Scott can no longer walk unsupported, has slurred speech and struggles with eating, including intermittent choking fits.
PSP is closely linked to Alzheimer's and Parkinson's disease and is often wrongly diagnosed as one of the two.
Specialists believe that due to misdiagnosis, the actual number of sufferers could well exceed 10,000.
Last Saturday, Mrs Scott’s family and friends held an awareness afternoon to raise money for the cause during the national PSP week.
The event was a success, raising £163 and afterwards her husband, John Scott, 75, was able to shed some more light on Clare’s illness.
He said: "I first realised something was wrong when Clare started falling backwards. After seeing a doctor, she was misdiagnosed with Parkinson’s.
"Later that year, we saw another specialist who was able to correctly diagnose the problem.
Since then, Clare has become progressively worse and now needs 24 hour supervision. She went into a nursing home in November of last year and they have had to take several special precautions with her.
"She kept getting out of bed in the middle of the night and falling over, so she now has a special one to make it easier.
"There is no treatment but there are ongoing trials for a drug called NP12 which is also being tested on Alzheimer’s patients.
"It wasn’t until Clare went into the nursing home that I realised how low I had got as the carer.
Clare is not affected mentally at all and she knows what’s happening all the time. She knows it’s getting worse."
Both Clare and John Scott were involved in a car accident in 2003 and John said that after the accident things started to go wrong. Clare had endometrial cancer which was successfully treated and it has not reoccurred since she was diagnosed with PSP.