Differential Diagnosis for Pustular Rash on Palms and Unilateral Knee Pain and Swelling
- Single Most Likely Diagnosis
- Psoriatic Arthritis: This condition is characterized by the combination of psoriasis (which can manifest as pustular rash on palms) and arthritis (leading to knee pain and swelling). The unilateral involvement of the knee is consistent with the asymmetric joint involvement often seen in psoriatic arthritis.
- Other Likely Diagnoses
- Reactive Arthritis: This form of arthritis occurs as a reaction to an infection elsewhere in the body, often in the gastrointestinal tract or the urethra. It can cause knee pain and swelling, and some patients may develop skin lesions, including pustular rashes.
- Gout: Although gout typically presents with acute, intermittent attacks of joint pain (often in the big toe), it can also affect the knee. The presence of a pustular rash on the palms could be unrelated or indicative of another condition, but gout should be considered, especially if there are risk factors such as hyperuricemia.
- Sarcoidosis: This systemic disease can cause arthritis and skin manifestations, including rashes. However, the specific combination of pustular rash on palms and unilateral knee involvement is less typical.
- Do Not Miss Diagnoses
- Septic Arthritis: Although less likely given the description, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. It can present with acute onset of joint pain and swelling, and if not treated, can lead to serious complications.
- Lyme Arthritis: Caused by the bacterium Borrelia burgdorferi, Lyme disease can lead to arthritis, typically affecting the knee. Early stages of Lyme disease can also include a rash (erythema migrans), but this is usually distinct from a pustular rash on the palms.
- Rare Diagnoses
- Multicentric Reticulohistiocytosis: A rare condition characterized by the development of skin nodules and erosive arthritis. The skin lesions can sometimes appear pustular, and the condition can mimic other forms of arthritis.
- SAPHO Syndrome (Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis): This rare condition involves the musculoskeletal system and skin, with manifestations that can include pustular dermatitis and arthritis. It's a diagnosis to consider when other explanations for the combination of skin and joint symptoms are not found.