Differential Diagnosis
- Single most likely diagnosis
- Cellulitis: The patient presents with swelling, redness, warmth, and pain to the left ankle, which are classic signs of cellulitis, a common skin infection. The scratch above the ankle from a bush provides a clear portal of entry for bacteria, making this diagnosis highly plausible.
- Other Likely diagnoses
- Septic arthritis: Given the patient's rheumatoid arthritis and the presence of pain in the left groin, which could be referred pain from the hip, septic arthritis is a possible diagnosis. The patient's immunosuppressed state due to Actemra increases the risk of infections.
- Deep vein thrombosis (DVT): The swelling, redness, and warmth in the ankle could also be indicative of a DVT, especially if the patient has been immobile or has other risk factors.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Necrotizing fasciitis: Although less common, this is a life-threatening condition that can present with similar symptoms to cellulitis. The patient's immunosuppressed state increases the risk, and prompt recognition is crucial.
- Osteomyelitis: An infection of the bone, osteomyelitis can occur in the context of a skin infection like cellulitis, especially if the scratch penetrated deeply. It's a serious condition that requires early diagnosis and treatment.
- Rare diagnoses
- Erythema nodosum: An inflammatory condition that can cause red, painful nodules on the skin, typically on the lower legs. While possible, it's less likely given the acute presentation and the presence of a scratch.
- Rheumatoid arthritis flare: Although the patient is on Actemra for rheumatoid arthritis, a flare could potentially cause similar symptoms. However, the localized nature of the symptoms and the presence of a scratch make this less likely.