Differential Diagnosis for Plaque Dermatitis on the Leg with Enlarged Groin Lymph Node in a Patient and Their Partner
- Single Most Likely Diagnosis
- Scabies: This is a highly contagious skin infestation caused by the mite Sarcoptes scabiei. The presence of similar symptoms in a sexual partner strongly supports this diagnosis, as scabies is commonly spread through close, prolonged skin-to-skin contact. The rash and intense itching, particularly at night, along with the presence of burrows on the skin, are characteristic. Enlarged lymph nodes can occur due to the body's immune response to the infestation.
- Other Likely Diagnoses
- Contact Dermatitis: This could be either irritant or allergic in nature. If the patient and their partner have been exposed to the same irritant or allergen (e.g., a new soap, lotion, or plant), it could explain the similar dermatitis presentations. However, the presence of enlarged lymph nodes might be less commonly associated with contact dermatitis unless there's a significant allergic reaction or secondary infection.
- Psoriasis: Although less likely to be simultaneously diagnosed in partners without a prior history, psoriasis can present with plaque-like lesions. The involvement of lymph nodes could be indicative of psoriatic arthritis or a severe form of psoriasis. However, the simultaneous onset in partners would be unusual.
- Do Not Miss Diagnoses
- Lymphoma (Cutaneous T-Cell Lymphoma): While rare, cutaneous lymphomas can present with skin lesions and lymphadenopathy. Mycosis fungoides, a type of cutaneous T-cell lymphoma, can mimic various dermatoses, including eczema or psoriasis, making it a critical diagnosis not to miss due to its potential for severe outcomes if left untreated.
- Infectious Diseases (e.g., Syphilis, HIV): Certain infectious diseases can cause skin rashes and lymphadenopathy. For example, secondary syphilis can present with a rash on the palms and soles and generalized lymphadenopathy. HIV can also cause a variety of skin manifestations and lymphadenopathy. These conditions are crucial to diagnose early due to their significant health implications.
- Rare Diagnoses
- Keratoderma Blennorrhagicum: Associated with reactive arthritis (formerly known as Reiter's syndrome), this condition can cause skin lesions similar to psoriasis, along with lymphadenopathy. It's typically seen in the context of a systemic disease and is less likely but should be considered in the appropriate clinical context.
- Granuloma Inguinale (Donovanosis): A sexually transmitted infection caused by Klebsiella granulomatis, characterized by genital ulcers that can spread to the groin area, potentially causing lymphadenopathy. While rare in many parts of the world, it's an important consideration in patients with risk factors for sexually transmitted infections.