Hence, other medical conditions that include tics or tic-like movements—for example, autism or other causes of tics—must be ruled out.Patients referred for a tic disorder are assessed based on their family history of tics, vulnerability to ADHD, obsessive–compulsive symptoms, and a number of other chronic medical, psychiatric and neurological conditions. In individuals with a typical onset and a family history of tics or OCD, a basic physical and neurological examination may be sufficient. There are no specific medical or screening tests that can be used to diagnose Tourettes; the diagnosis is usually made based on observation of the individuals symptoms and family history, and after ruling out secondary causes of tic disorders (tourettism).Delayed diagnosis often occurs because professionals mistakenly believe that TS is rare, always involves coprolalia, or must be severely impairing. The DSM has recognized since 2000 that many individuals with Tourettes do not have significant impairment; diagnosis does not require the presence of coprolalia or a comorbid condition, such as ADHD or OCD. Tourettes may be misdiagnosed because of the wide expression of severity, ranging from mild (in the majority of cases) or moderate, to severe (the rare but more widely recognized and publicized cases). About 20% of people with Tourette syndrome do not realize that they have tics.Tics that appear early in the course of TS are often confused with allergies, asthma, vision problems, and other conditions.
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This article incorporates public domain text from The U.S. National Library of Medicine and the National Institute of Neurological Disorders and Stroke. External links

GeneReviews/UW/NIH entry on Coffin–Lowry syndrome
Coffin-Lowry syndrome: MedlinePlus Genetics