Book excerpt: Troublesome Disguises examines psychiatric conditions which are not necessarily uncommon, rare or exotic but are challenging for the clinician who may struggle to reach a diagnosis and to set up management strategies. However, with familiarity, these conditions can and should be recognised. This new edition is an exercise in consciousness-raising as well as a warning to beware of diagnostic systems which, despite their many virtues, may become too influential and may perpetuate errors which are to the detriment of patients. For the clinician struggling to understand and treat patients who fail to fit the usual diagnostic categories, Troublesome Disguises provides wise instruction in the virtue of entertaining doubts, as well as practical advice for the assessment and management of atypical cases.