Differential Diagnosis for Violaceous, Pruritic Papular Rash
- Single most likely diagnosis
- Lichen planus: The description of a violaceous, pruritic papular rash along with histological findings of hyperkeratosis, irregular acanthosis, and focal thickening in the granular layer is highly suggestive of lichen planus. Lichen planus is known for its characteristic clinical and histological features, including the presence of Civatte bodies and a band-like lymphocytic infiltrate, which are not mentioned but are typical for this condition.
- Other Likely diagnoses
- Psoriasis: While psoriasis can present with a pruritic rash and histological features like hyperkeratosis and acanthosis, the violaceous color and specific granular layer changes are less typical for psoriasis. Psoriasis usually shows parakeratosis (nuclei present in the stratum corneum), which is not mentioned.
- Inverse psoriasis: This form of psoriasis occurs in intertriginous areas and can present with a violaceous hue due to the thinning of the epidermis. However, the histological description provided does not fully align with the typical features of inverse psoriasis, such as spongiosis and lack of granular layer, but it remains a consideration due to the clinical description.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- None are immediately apparent from the provided description that would fit into a "do not miss" category based on the potential for being deadly if missed. However, conditions like drug eruptions or cutaneous T-cell lymphoma (e.g., mycosis fungoides) could present with similar symptoms and should be considered in a broader differential, especially if the patient's history or response to treatment suggests an alternative diagnosis.
- Rare diagnoses
- Lichenoid drug eruptions: These can mimic lichen planus both clinically and histologically but are caused by medications. The presence of eosinophils in the infiltrate might suggest this diagnosis.
- Keratosis lichenoides chronica: A rare condition with lichenoid histology but typically presents with a more chronic course and specific clinical features like a reticulated or linear pattern of the lesions.