In diagnosis, it is particularly important not to miss treatable disorders. A classic example of such a situation is Wilson disease, an abnormality of copper metabolism that can be rapidly fatal but easily treated if caught early. Wilson disease can present with many different combinations of findings. As a result of this complexity, the diagnosis of Wilson disease is often missed for years.
Example to work through
A 20-year-old man had onset over several years of dysarthric speech, personality change, and psychotic thought patterns without hallucinations. Wilson disease is in the differential diagnosis, but with a low probability shared by several other diagnoses. Yet, the abnormal iris pigmentation characteristic of Wilson disease is ranked high in the list of useful findings because it is highly useful to diagnose a treatable disease. Wilson disease is not ranked as more likely in the differential diagnosis because it is treatable, but the iris finding is ranked high in the list of Useful findings. (Registered users can click the image below to jump into the software; some videos may be helpful in navigating from there)
The error associated with ignoring treatability would be to miss the opportunity to make a diagnosis of a condition that is very treatable (and in this case, fatal if left untreated).
This page is part of a series on the Elements of Diagnosis.
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