Differential Diagnosis for the 16-year-old Female Patient
- Single most likely diagnosis
- Contact dermatitis (e.g., poison ivy, oak, or sumac): This is the most likely diagnosis given the patient's recent outdoor activity at Girl Scout camp, the description of the rash as red bumps that are extremely itchy, and the distribution of the rash on extremities, posterior neck, and face. The fact that the rash started after exposure to the outdoors and has progressed over time also supports this diagnosis.
- Other Likely diagnoses
- Insect bites (e.g., mosquito, chigger, or flea bites): The itchy red bumps could be consistent with insect bites, especially given the outdoor setting. However, the distribution and progression of the rash might be less typical for some types of insect bites.
- Allergic reaction to an unknown substance: The patient's symptoms could also be consistent with an allergic reaction to something she was exposed to at camp, such as a plant, animal, or chemical. The lack of systemic symptoms (e.g., shortness of breath, lip swelling) makes this less likely but still possible.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Anaphylaxis: Although the patient denies shortness of breath, lip swelling, or difficulty swallowing, anaphylaxis can present in various ways, and it's crucial to consider this diagnosis, especially if the patient's condition worsens or if there are any signs of airway compromise.
- Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN): These are severe skin conditions that can be life-threatening. While the patient's current symptoms do not strongly suggest SJS/TEN, any sign of skin necrosis, mucosal involvement, or systemic illness would necessitate immediate medical attention.
- Rare diagnoses
- Erythema multiforme: This is an immune-mediated condition characterized by target-like lesions. It's less likely given the description of the rash as red bumps, but it could be considered if the rash has a distinctive targetoid appearance.
- Zoster (shingles): Although shingles typically presents with a dermatomal distribution and is less common in young individuals, it's a rare possibility if the patient has had varicella (chickenpox) in the past and is now experiencing a reactivation of the virus. However, the lack of a clear dermatomal pattern and the patient's age make this diagnosis less likely.