Dermatology and Psychiatry: Description, Classification, Safety
Core concepts
Dermatology rewards precise description. Learn to describe a lesion by site, distribution, morphology, colour, surface and arrangement, then use that description to narrow the differential. Know the common patterns: papulosquamous disease, vesiculobullous disease, eczematous eruptions, and drug reactions. Understand the difference between a macule, papule, plaque, vesicle, bulla and pustule. Recognise emergencies: Stevens–Johnson syndrome and toxic epidermal necrolysis, necrotising fasciitis, and angio-oedema with airway compromise. Know the significance of a changing pigmented lesion and the ABCDE approach.
Psychiatry questions test classification, risk assessment, and safe management. Understand the core features of psychosis, mood disorders, anxiety disorders, and delirium versus dementia. Learn the principles of the mental state examination and the assessment of suicide risk. Know the major psychotropic classes, their key side effects, and the monitoring they require.
Traps
Examiners often present a patient whose physical symptoms are explained by an underlying medical condition - always exclude organic causes before a psychiatric diagnosis. In dermatology, beware of the lesion described as 'itchy' when the diagnosis is a serious condition. Distinguish delirium (acute, fluctuating, impaired attention) from dementia (chronic, progressive).
Rule of thumb
In psychiatry, assess risk first: risk to self, risk to others, and risk from self-neglect. In dermatology, if a lesion is changing or ulcerated, it needs histological assessment.
Worked example
A patient on a new anticonvulsant develops fever, widespread painful skin, and mucosal erosions with skin peeling. This is Stevens–Johnson syndrome or toxic epidermal necrolysis; the answer is immediate withdrawal of the drug, supportive care, and urgent specialist input.