Case 4: Differential Diagnoses

Incorrect. This is a young woman with symmetric inflammatory arthritis affecting MCPs and PIPs. OA generally affects older individuals, typically involves DIPs and PIPs, and weight bearing joints, such as knees. Try again!

While FM can certainly co-exist with any disorders that cause pain, this young woman has clear inflammatory findings in her joints, which is not expected with FM. Keep trying!

Correct! Patients presents with over 6 weeks of symmetric inflammatory arthritis of small joints of hands and family hx of arthritis in mother at a young age. This is very consistent with RA. Great job!

Good thought! Parvovirus can present with joint swelling for weeks, but it seems unlikely without exposures. Patient has a newborn rather than a toddler and denies exposure to other children. Further workup and time will help distinguish between parvovirus B-19 and the more likely diagnosis in this case.

Excellent thinking! Spondyloarthritis (SpA), such as psoriatic arthritis or reactive arthritis, are on the differential diagnosis for inflammatory arthritis. Asymmetric joint swelling along with other potential findings, such as inflammatory eye disease, IBD, psoriasis, nail pitting/oil staining/onycholysis, enthesitis, inflammatory back pain would make SpA more likely than RA. Further studies will help us distinguish between them as well.

Autoimmune diseases such as SLE, MCTD, Sjogren’s, etc can present with inflammatory arthritis. We would expect to see other findings such as photosensitive rashes, mouth/nasal ulcers, sicca symptoms, Raynaud’s, etc, which patient currently lacks. These should be kept in mind, however, as inflammatory arthritis can be the first manifestations and autoimmune diseases can overlap.

Endocrinopathies, such as thyroid disease, can cause joint pain and even mild swelling. Patient lacks other specific symptom or signs of hypo- or hyperthyroidism, making this less likely than primary inflammatory arthritis.

Although septic arthritis should always be considered when acute monoarthritis develops, symmetric polyarticular swelling of small joints of hands would be unusual. Of note, gonococcal arthritis can cause polyarticular swelling, tenosynovitis, and skin nodules but patient is in a monogamous relationship and lacks any other signs of infection. She has likely gotten tested for STDs during pregnancy as well.

Crystalline arthritis is certainly on DDx for inflammatory arthritis. Pseudogout can present in a similar pattern to OA, RA, gout, or even Charcot’s neuropathy. Patient’s age makes this diagnosis unlikely.