Psoriasis in a patient with inflammatory joint pain is often missed for the same two reasons: the patient does not connect the two, and the examination stops at the joints. Both are fixable in the time it takes to ask one more question.
Ask directly rather than generally. 'Any skin problems?' produces a no from a person who thinks their scalp flaking is dandruff. Ask whether anyone has ever told them they had psoriasis, whether they have scaling on the scalp, behind the ears, in the umbilicus or the natal cleft, and whether their nails have changed. Then look at those places yourself, and at the nails specifically - pitting, onycholysis and subungual hyperkeratosis are the most useful signs in the room, and nail disease is more strongly associated with psoriatic arthritis than skin extent is.
The same applies in the other direction. A patient who already carries a psoriasis diagnosis and reports fatigue and joint pain is not describing two unrelated complaints, and the fact that their skin is mild says very little - severity of skin disease and presence of arthritis are only loosely linked.
- Ask about scalp, behind the ears, umbilicus and natal cleft by name, not about 'skin problems' in general
- Examine the nails in every patient with inflammatory joint pain - pitting and onycholysis are the highest-yield signs
- Ask about family history of psoriasis; it is frequently the only clue in a patient with no visible skin disease
- Do not use skin severity to gauge joint risk - mild psoriasis is not reassuring
- Record what you examined, so the next clinician does not repeat a negative history from a patient who answered the wrong question
Why it matters
The diagnosis often turns on a patch of skin the patient does not think is worth mentioning.
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