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1. 20-30% of patients who have nail pitting, onycholysis (separation of the nail from the nail bed), and "oil spots" (brownish discoloration under the nails) also develop joint disease.

2. Symmetric polyarthritis: looks like RA; can involve the PIPs, MCPs, knees.

3. Asymmetric arthritis (e.g., oligoarthritis): usually involves large joints like the knees, ankles, and wrists; typically < 3 joints are affected.

4. Spondylitis: similar to AS with inflammatory back pain, but x-rays show an asymmetric sacroiliitis.

5. DIP arthritis: looks like OA, but there is evidence of nail psoriasis.

6. Arthritis mutilans: severe resorptive destruction of the joint.

7. SUMMARY: Sausage-shaped digits are common only in reactive arthritis and psoriatic arthritis. Ice pick-like pitting of the nails is very specific for psoriatic arthritis.


1. Wilkinson, I. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press.
2. Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
3. Image: no reference available.

Ⓒ A. Manickam 2018

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