The disorder affects approximately 1 out of 10,000 people. None is known, but treatment of the disorder prevents recurrence. Reflexes are often abnormal. Muscles may develop spasticity . Mental changes are variable, from mild forgetfulness to complete dementia or psychosis .
Severe dementia is uncommon, but in some cases, it is the initial symptom of the disorder.
A CBC may show anemia if pernicious anemia is also present. If folic acid has been used to treat anemia, neurologic symptoms may develop even if the anemia is no longer evident. Serum B12 levels are low. Early treatment improves the chance of a good outcome, so the disease should be treated promptly. Vitamin B12 is given, usually by intramuscular injection, in large doses.