PANDAS can present with chorea but more typically there are tics, stereotypies with a psychological component (e.g., OCD). Differential diagnosis
Other disorders that may be accompanied by chorea include benign hereditary chorea, bilateral striatal necrosis, abetalipoproteinemia, ataxia–telangiectasia, biotin-thiamine-responsive basal ganglia disease, Fahr disease, familial dyskinesia–facial myokymia (Bird–Raskind syndrome) due to an ADCY5 gene mutation, glutaric aciduria, Lesch–Nyhan syndrome, mitochondrial disorders, Huntingtons disease, Wilson disease, hyperthyroidism, lupus erythematosus, pregnancy (chorea gravidarum), drug intoxication and side effects of certain anticonvulsants (e.g. phenytoin) or psychotropic agents. Although some of these can similarly present in an acute way, there will typically be other neurological signs (such as ataxia or cognitive impairment), or other disease manifestations, or positive family history, which will help distinguish between them. Pathology
One of the important manifestations of acute rheumatic fever, Sydenhams chorea is similarly caused by an autoimmune response following infection by group A β-hemolytic streptococci.Two cross reactive streptococcal antigens have been identified, the M protein and N-acetyl-beta-D-glucosamine, whereby infection leads to autoantibodies being produced against host tissues (molecular mimicry) causing a variety of streptococcal related diseases including Sydenhams chorea but also rheumatic heart disease and nephritic syndrome. Autoantibodies against basal ganglia proteins have been found in Sydenhams chorea but these are non-specific. Dopamine receptor autoantibodies have been reported to correlate with clinical symptoms. Whether these antibodies represent an epi-phenomenon or are pathogenic, remains to be proven. Epidemiology
As with rheumatic fever, Sydenhams chorea is seen more often in less affluent communities, whether in the developing world or in aboriginal communities in the global North.
There is usually loss of fine motor control, particularly obvious in handwriting if the child is of school age. Speech is often affected (dysarthria), as is walking; legs will suddenly give way or flick out to one side, giving an irregular gait and the appearance of skipping or dancing. Underlying the abnormal movements is often low tone (hypotonia) which may not become obvious until treatment is started to suppress the chorea. In severe cases, the loss of tone and weakness predominate (chorea paralyticum). The severity of the condition can vary from just some instability on walking and difficulty with hand writing, to the extreme of being wholly unable to walk, talk, or eat. Movements cease during sleep. The eye muscles are not affected, curiously.It is a neuropsychiatric disorder, so besides the motor problems there is classically emotional lability (mood swings, or inappropriate mood), anxiety, attention deficit. These can precede the motor symptoms.Non-neurologic manifestations of acute rheumatic fever may be present, namely carditis (up to 70% of cases, often subclinical, so echocardiography required), arthritis, erythema marginatum, and subcutaneous nodules. Differentiating these signs from other involuntary movements such as tics and stereotypies can be difficult, and since these things are not uncommon they can potentially co-exist. Diagnosis is often delayed and attributed to another condition such as tic disorder or conversion disorder. The controversial PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections) hypothesis has overlapping clinical features but Sydenhams chorea is one of the exclusion criteria.