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Chorea (Greek for “dance”) consists of irregular, unpredictable, brief movements that flow from one body part to another in a nonstereotyped fashion. They may be incorporated, especially in milder cases, into more purposeful movements. They may consist of small twitches or larger jerks of any body part. Choreiform movements rarely occur in isolation; rather, they may be often seen in a spectrum with slower, distal, writhing, sinuous movements called athetosis, and described as choreoathetosis. In many disorders in which chorea is a feature, it is not uncommon to see other movement disorders as well, particularly dystonia. The converse of speed and amplitude from athetoid movements are ballistic movements (i.e., fast and large amplitude), which are usually seen unilaterally as hemiballism, although bilateral (paraballism or biballism) may be encountered. Ballistic movements, the most extreme type of movement disorder, are large amplitude, usually proximal flinging of a limb or body part. Although some investigators separate these disorders, others (including the present author) consider ballism to be a severe form of chorea, and in fact many cases of resolving ballistic movements taper down to chorea.1

The prototypic choreic disorder is Huntington's disease (HD), discussed in detail in the preceding chapters (see Chapters. 32, 33 and 34). The phenomenology of chorea in other disorders, both primary and secondary, is essentially the same as in HD; likewise, theories of the pathophysiology of the choreas, for the most part, are very similar. Similarly, Wilson's disease (see Chapter. 42), tardive dyskinesia (see Chapter. 35), and treated Parkinson's disease (see Chapter. 13, and 15) may also demonstrate chorea; the reader is referred to those chapters for more details. In this chapter, we will focus on several clinical entities in which chorea plays a significant role. Other related movement disorders will also be discussed.

It has long been recognized that several seemingly unrelated conditions have been uncommonly associated with chorea: rheumatic fever, systemic lupus erythematosus (SLE), and pregnancy (and its flip side, use of oral contraceptives). The pathophysiology of chorea in these conditions may be similar and will be explored below.

Sydenham's Chorea

In 1686, Thomas Sydenham described the clinical syndrome that now bears his name.2 Originally called St Vitus dance, as well as chorea minor, acute chorea, and rheumatic chorea, Sydenham's chorea (SC)not uncommonly follows rheumatic fever in children and adolescents. Antecedent infection with group A streptococcus is usual, although many patients do not give a history of streptococcal infection; and, as the chorea may occur 6 months or more after infection, antistreptolysin and antistreptococcal antibodies may not be elevated. Adequate antibiotic therapy has dramatically reduced the occurrence of rheumatic fever in the United States, and thus of SC,3 although it may still be found. It may be seen more often in children from developing countries who lack routine antibiotic care. In fact, a series from Turkey in the mid-1990s ...

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