What is the diagnosis?
Before taking a more extensive history, it is appropriate to look at her fingers more closely to collect data that will inform questioning. By applying pattern recognition skills first, you can form hypotheses and use the remainder of the exam to test them.
How would you describe the abnormalities seen in Figure 1 and Figure 2 (pattern recognition), and what would be the differential diagnosis (hypotheses)?
What further history, physical exam, or laboratory tests should be completed (hypothesis testing)?
FIGURE 1
This patient’s fingernail had been discolored for months and the fingertip had recently begun to hurt.
A brown discoloration (oil spot) in the patient’s proximal nail.
Figure 1 shows a brownish discoloration of the fingernail, with small pits particularly prominent around the lunula (the semicircular light area adjacent to the proximal nail fold). There is also evidence of onycholysis (separation of the nail from the nail bed). The vertical ridging is not abnormal.
Figure 2 shows a well-circumscribed brown discoloration in the proximal nail called an oil spot. These nail findings are classic for psoriasis.1
Figure 1 also shows subtle swelling of the distal interphalangeal (DIP) joint. It is this area the patient said was painful, and she had joint tenderness to palpation over this DIP joint only.