Differential Diagnosis for a 26-year-old Female with a Rash on Hands and Feet
- Single most likely diagnosis:
- Erythema Multiforme (EM): This condition is characterized by targetoid lesions, which are described in the patient's presentation. The recent history of oral herpes simplex virus (HSV) infection, for which she was diagnosed ten days ago, is a common trigger for EM. The sharply demarcated, targetoid macules with dark red centers on the palms, soles, and other areas are classic for this diagnosis.
- Other Likely diagnoses:
- Secondary Syphilis: This condition can cause a rash on the palms and soles, although it is less common. Given the patient's recent sexual activity implied by the use of doxycycline for acne, syphilis should be considered, especially if other symptoms like lymphadenopathy are present.
- Gianotti-Crosti Syndrome: This is a rare condition but can be considered in the differential due to the rash's appearance on the hands and feet. It is often associated with viral infections, including hepatitis B and Epstein-Barr virus, but the targetoid appearance is less typical.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN): Although less likely given the lack of mucosal involvement and the description of the rash, SJS/TEN are life-threatening conditions that can be triggered by medications (like doxycycline) and infections. The presence of targetoid lesions and the recent medication use necessitate consideration of these conditions.
- Rocky Mountain Spotted Fever (RMSF): This tick-borne illness can cause a rash on the hands and feet, although it typically starts as a fever and headache. Given the potential for severe outcomes if untreated, RMSF should be considered, especially if the patient has been exposed to ticks.
- Rare diagnoses:
- Kawasaki Disease: Although primarily a disease of children, Kawasaki disease can occur in adults and is characterized by fever, rash, and other systemic symptoms. The rash can appear on the hands and feet, but the overall clinical picture and age make this a less likely diagnosis.
- Pityriasis Rosea: This condition typically starts with a herald patch followed by a widespread rash, usually on the trunk. While it can appear on the hands and feet, the description provided does not closely match pityriasis rosea, making it a less likely consideration.