Differential Diagnosis for Lichen Planus When considering the clinical signs that point to a lichen planus diagnosis, several other conditions should be taken into account to ensure accurate diagnosis and appropriate treatment. The differential diagnoses can be categorized as follows:
Single Most Likely Diagnosis
- Lichen planus: This is the most likely diagnosis when considering the characteristic clinical signs such as purplish, itchy, and polygon-shaped lesions, often found on the skin, mucous membranes, or both. The presence of these signs, especially in a middle-aged adult, strongly points towards lichen planus.
Other Likely Diagnoses
- Psoriasis: Characterized by red, scaly patches, psoriasis can sometimes be confused with lichen planus, especially if the lesions are not typical. However, psoriasis tends to have a more silvery scale and often involves the elbows, knees, and scalp.
- Dermatitis (e.g., atopic, contact): Various forms of dermatitis can present with itchy lesions, but they usually lack the distinct polygonal shape and coloration of lichen planus. The distribution and history (e.g., exposure to allergens) can help differentiate dermatitis from lichen planus.
- Eczema: Similar to dermatitis, eczema presents with itchy lesions but tends to have a different distribution and often involves the face, hands, and feet in adults.
Do Not Miss Diagnoses
- Lupus erythematosus: Although less common, systemic lupus erythematosus (SLE) can present with skin lesions that resemble lichen planus. Missing this diagnosis could be critical due to the potential for systemic involvement and the need for different management strategies.
- Pemphigus: An autoimmune disease that causes blistering of the skin and mucous membranes. While it's less likely, the mucosal involvement could mimic some aspects of lichen planus, and missing this diagnosis could lead to severe consequences due to the potential for widespread blistering and infection.
Rare Diagnoses
- Lichenoid drug eruptions: Certain drugs can cause eruptions that mimic lichen planus. This is a rare but important consideration, especially in patients who have recently started new medications.
- Chronic arsenic poisoning: Can cause skin lesions that resemble lichen planus, among other systemic effects. This is rare in most populations but should be considered in the appropriate context (e.g., exposure history).
- Other lichenoid reactions (e.g., due to hepatitis, systemic trauma): These are rare conditions that can mimic lichen planus but are associated with specific underlying conditions or exposures.