Decision trees are a convenient means of elucidating the steps that inform differential diagnosis. Each decision tree starts with a particular presenting symptom and then provides decision points for determining which diagnosis may best account for it. For any given patient, several trees may (and often do) apply. In many instances, following the branches within the different pertinent decision trees will lead to the same diagnosis, suggesting that the presenting symptoms constitute a single syndrome. In other instances, more than one diagnosis may be indicated.