Differential Diagnosis for Palmar Rash
- Single most likely diagnosis
- Palmar-plantar erythrodysesthesia syndrome (PPE): This condition is a common side effect of certain chemotherapy agents, which the patient may have been exposed to during immunotherapy for lung cancer. The patient's recent history of immunotherapy and the location of the rash on the palms make PPE a likely diagnosis.
- Other Likely diagnoses
- Contact dermatitis: The patient's use of OTC steroid cream without relief does not rule out contact dermatitis, as the cream may not have been potent enough or used for a sufficient duration. The patient may have come into contact with an irritant or allergen that caused the rash.
- Psoriasis: The patient's symptoms of a rash on the palms, although not typical of psoriasis, could be a variant of palmoplantar psoriasis. The temporary relief with prednisone also supports this diagnosis.
- Dyshidrotic eczema: This condition is characterized by a rash on the palms or soles, which could fit the patient's presentation. However, the lack of other symptoms such as vesicles or pruritus makes it less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Malignant acanthosis nigricans: Although rare, this condition is associated with internal malignancies and can present with a rash on the palms. Given the patient's history of lung cancer, it is essential to consider this diagnosis.
- Sweat gland carcinoma: This rare tumor can present with a rash on the palms and is often associated with a poor prognosis. Early detection is crucial, making it a "do not miss" diagnosis.
- Rare diagnoses
- Keratoderma blennorrhagicum: This rare condition is associated with Reiter's syndrome and can present with a rash on the palms. However, the patient's lack of other symptoms such as arthritis or conjunctivitis makes it less likely.
- Pityriasis rubra pilaris: This rare skin disorder can present with a rash on the palms, but it is often accompanied by other symptoms such as keratotic papules or follicular hyperkeratosis, which are not mentioned in the patient's presentation.