Differential Diagnosis for Rash Starting on Wrist and Hands
Single Most Likely Diagnosis
- Atopic Dermatitis (Eczema): Given the itchy nature of the rash and its initial appearance on the wrists and hands before generalizing, atopic dermatitis is a strong consideration. The lack of response to benadryl and cortisone cream does not rule out this diagnosis, as some cases can be resistant to initial treatments.
Other Likely Diagnoses
- Contact Dermatitis: This could be either irritant or allergic in nature. The initial appearance on the wrists and hands suggests exposure to an allergen or irritant, which then spread. The lack of response to cortisone cream might indicate a need for a different potency or type of topical steroid.
- Psoriasis: Although less common to start as a generalized rash from the hands, psoriasis can present with itchy, scaly plaques and might not respond immediately to over-the-counter treatments like cortisone cream.
- Seborrheic Dermatitis: Typically affects areas rich in sebaceous glands but can spread and might present with itchy lesions.
Do Not Miss Diagnoses
- Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): Although rare, these conditions are life-threatening and can start with a rash that might seem benign initially. The lack of response to standard treatments and progression of the rash are red flags.
- Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): A severe drug reaction that can present with a rash, fever, and systemic symptoms. It's crucial to identify and stop the offending drug.
- Pemphigus or Pemphigoid: Autoimmune blistering diseases that can present with itchy, blistering rashes and might not respond to conventional treatments.
Rare Diagnoses
- Pityriasis Rubra Pilaris: A rare skin disorder characterized by constant scaling, redness, and keratotic follicular papules.
- Keratosis Pilaris: While not typically itchy to the degree described, in rare cases, it can present with more severe symptoms.
- Cutaneous T-cell Lymphoma (Mycosis Fungoides): A rare type of skin cancer that can mimic various dermatoses, including eczema or psoriasis, and might not respond to standard treatments.