142

papers published on SCA12

1999–2026

years of research

1

randomised treatment trial, ever

None

treatments that slow the condition

Or go straight to the library: all 142 papers, year by year

Start here

Twenty-seven years in seven moments

SCA12 research is small enough that its whole history fits on one screen. Each entry links to the paper it comes from.

1999

A new ataxia is named

In one American family of German descent, researchers at Johns Hopkins found a long CAG repeat in front of a gene called PPP2R2B and called the condition SCA12. The first paper.
2001

India turns out to be where it lives

A team at AIIMS New Delhi found SCA12 in five of 77 Indian families with inherited ataxia, and wrote that it "may not be as rare in some populations as previously thought". Srivastava and colleagues.
2005

One ancestor, many families

All twenty Indian families studied shared the same stretch of DNA around the repeat, meaning the expansion happened once, long ago, in one endogamous community. The founder study.
2008

The first idea of what goes wrong

The protein the gene makes was shown to break up mitochondria, the parts of a cell that make its energy, and to make nerve cells more likely to die. Dagda and colleagues.
2017

The threshold moves

AIIMS and CSIR-IGIB described 18 patients with 43 to 50 repeats who looked like everyone else with SCA12, and proposed 43 as the level at which the test should be called positive. Published in Brain.
2023

A second theory arrives

The expanded repeat was shown to make RNA that clumps inside the cell nucleus and is read into unusual small proteins, a mechanism seen in other repeat diseases. Reported in 2023 and confirmed in 2024.
2026

The first treatment trial in 27 years

Sixty patients at AIIMS were given either long-acting propranolol or a placebo. The drug reduced tremor and improved balance scores and quality of life over eight weeks. The trial report.

The shape of it

What the papers are actually about

Our own grouping of all 142 papers, by reading each title and abstract. It shows where the effort has gone, and where it has not.

The gene and who carries it

27 papers

The repeat itself, the threshold for calling a test positive, and screening studies asking how common SCA12 is in a population. The largest group by far, and the reason the condition is well defined but poorly understood.
What it looks like in people

29 papers

Symptoms, case reports and studies of groups of patients. This is where the description of tremor first, ataxia later, comes from.
What goes wrong inside cells

21 papers

Laboratory work on the gene and the protein it makes, in cells, flies and stem cell lines. Almost none of it has yet been confirmed in human brain tissue.
Scans, tests and measurements

18 papers

Brain imaging, eye movement and tremor recordings, and attempts to find a marker in blood. Mostly small studies from one centre each.
Treatment and therapy

5 papers

Everything ever tried for the condition, from the 2026 propranolol trial down to single case reports of surgery. The smallest group, and the one that matters most to a patient.
Reviews and chapters

16 papers

Summaries of other work. Useful maps, but they add no new evidence of their own.
Mentions SCA12 in passing

26 papers

Papers that appear in the library because they name SCA12 or the gene, but are really about another condition or another question.

Counted once each: a paper is placed where its main subject lies. The imbalance is the point. Far more work has gone into finding out who carries the expansion than into what to do for the people who have it.

How to read a library

Papers do not all carry the same weight

This is the single most useful thing to know when reading about any condition. A finding from the top of this pyramid is worth far more than the same claim from the bottom, and headlines rarely say which one they are quoting.

2 studies that tried a treatment

The strongest design gives one group the treatment and another a dummy, then compares them. That is the only way to show a treatment works rather than that people happened to improve.

Both are from 2026. Only one was built that way: propranolol against placebo in 60 people. Read it. The other gave dance movement therapy to eight people with no comparison group, so its gains cannot be separated from the effect of attention and company. Read it.
52 studies of groups of patients

A group of patients is described, or a population is screened. These tell you what the condition looks like and how common it is, but not whether anything helps.

The largest is 49 patients seen in Bengaluru. Read it.
24 single patients or small groups

One person is described in detail. Valuable for showing that something is possible, useless for showing how often it happens. A treatment that helped one person may help nobody else.

Reports of focused ultrasound and deep brain stimulation for severe tremor are of this kind. One example.
37 laboratory studies

Work in cells, flies, mice or computers. This is where an understanding of the disease is built, but a result in a dish is a long way from a result in a person.

Patient stem cell lines and a fruit fly model both exist. One example.
16 reviews and chapters

A summary of other people’s work. Useful as a map, but it adds no new evidence, and it can repeat an error from an older paper for years.

The 2026 review is the best current one. Read it.
9 conference abstracts

A few hundred words submitted to a meeting, usually with no peer review and often never published in full. Treat the findings as provisional.

Several SCA12 imaging results exist only in this form.

The counts are our grouping of the same papers, this time by the kind of evidence rather than the subject. 2 of the 142 fit none of these rungs and are left out. Anything you read about SCA12, anywhere, can be placed on this ladder before you decide how much weight to give it.

The science

What may be happening inside the cell

This is where a treatment would have to act, so it is worth understanding in outline. Read the colours: the first two stages are established in people, the middle is laboratory work, and the last box is the honest gap.

The gene

Everyone has the PPP2R2B gene. It makes part of an enzyme, PP2A, that nerve cells use constantly. Source.

Shown in people
The change

In SCA12 a run of CAG letters in front of the gene is too long. Unlike Huntington’s disease, this stretch is not turned into a protein. Source.

Shown in people
What that might do

The cell makes too much of one form of the protein.

Cells or animals only

The long repeat makes RNA that clumps in the cell nucleus.

Cells or animals only

Those clumps are read into unusual small proteins.

Cells or animals only
The damage

Mitochondria, the cell’s power supply, break up and nerve cells die. Antioxidants partly rescue this in flies.

Cells or animals only

Which of these actually harms the brain of a person with SCA12.

Not shown yet

Shown in people with SCA12 Shown in cells or animals only Not shown anywhere yet

A treatment that slowed SCA12 would have to interrupt one of the middle boxes. That is why it matters that nobody yet knows which of them is doing the harm in a human brain, and it is a fair question to put to any researcher who asks your family to join a study.

The honest picture

Settled, emerging, and never studied

Most descriptions of a rare condition quietly leave out the third column. For a family deciding what to expect, it is often the most important one.

Settled

Reported consistently, by more than one group.

The cause is a long CAG repeat in front of PPP2R2B, and one copy is enough to cause the condition. Each child of an affected parent has a 50% chance of inheriting it. Source.
In North India it is concentrated in one community through a single common ancestor, and at one referral centre it was about one in six families with inherited ataxia. Source.
The first symptom for about three in four people is a tremor of the arms in use, often mistaken for essential tremor. Unsteadiness follows years later. Source.
Scans show shrinkage of the cerebellum and of the outer layer of the brain. Source.
Propranolol reduces tremor. This is the only treatment tested in a proper trial. Source.

Emerging

Real findings, but early, small, or not yet repeated.

Two competing explanations of what damages nerve cells, both being pursued in patient-derived stem cells. One, the other.
What a borderline result of 40 to 50 repeats means for one person. People in this range have typical disease, but nobody can say how often. Source.
Changes on scans in people who carry the expansion but have no symptoms yet. None of this predicts when symptoms start. Source.
Procedures for severe tremor. Single cases of focused ultrasound, deep brain stimulation and spinal cord stimulation report good control, though one unpublished case worsened balance. Source.
Dance movement therapy improved anxiety, depression and quality of life in a pilot of eight people, with no change in ataxia. Source.

Never studied

Not absent from this page by oversight. No paper covers it.

How the condition progresses over years. The only follow-up study covers three people. Source.
Life expectancy. Two papers say longevity may not be greatly affected, but no study has measured survival. Source.
What proportion of people who carry the expansion go on to develop symptoms, and by what age. Source.
Any treatment intended to slow the condition itself. None has been tested in a person.
A mouse that shows the disease. One exists, but nothing about it has been published. Source.
Children, pregnancy and anaesthesia in SCA12. No paper in the library addresses them.

If you read nothing else

The three questions that decide the next decade

What actually damages the nerve cells?

Laboratory work has produced several suspects, all traced to the same gene. No one has shown which of them, if any, is doing harm in the brain of a person with SCA12, and no drug aimed at any of them has been given to a patient.
How will this unfold for one person?

Almost nothing has been measured over time. The only follow-up study covers three people, and nobody can say what a borderline gene result means for someone who has no symptoms yet.
Can anything besides tremor be treated?

One drug has been shown to help tremor in a trial. Unsteadiness, the other core symptom, has no treatment proven to work, and the approaches specialists have been calling for since 2019 have still not been tried in SCA12.

Do it yourself

How to look something up

Everything on this page came from papers anyone can find. Here is how to check any of it, or to search for something we have not covered.

Start with our library: The research page lists every paper on SCA12, newest first, with a free-to-read filter. If a paper has free full text, the badge says so.
PubMed: The public index of medical research, run by the United States National Library of Medicine. Every number in brackets on this page is a PubMed identifier and links straight to the record.
The abstract is not the paper: An abstract is the summary the authors chose to write. It states results at their most favourable. Where the full paper is free, read the numbers in it.
Check how many people: The first thing to look for in any clinical claim. Fifty patients means something. One patient means it happened once.
Check whether there was a comparison group: Without one, improvement can be the natural course, the placebo effect, or a good week. This is what separates the top of the pyramid from the rest.
Watch for cells, flies and mice: Most SCA12 papers about mechanism are laboratory work. A finding there is a lead, not a treatment. Ask whether it has ever been shown in people.
Ask us: If you find a paper you cannot get hold of, or one you think we have missed, write to us. We read everything and we maintain the list by hand.

What SCA12 research adds up to