Differential Diagnosis for the 38-year-old Male Patient
Single Most Likely Diagnosis
- Congenital skin mark: Dr. Lopez's assessment suggests that the lesion could be a benign congenital skin mark, which would explain the absence of other symptoms and negative test results. The fact that it has been present for a year without significant change supports this diagnosis.
Other Likely Diagnoses
- Fixed drug eruption: Although the patient does not mention taking any new medications, a fixed drug eruption could cause a painful and pruritic lesion, especially if it is related to a specific medication taken around the time of sexual intercourse.
- Contact dermatitis: Irritation from a condom, lubricant, or other substance could cause a skin reaction, leading to a painful and itchy lesion.
- Neuropathic pain: The referral to neurology suggests that the pain may be neuropathic in origin, possibly related to nerve damage or irritation.
Do Not Miss Diagnoses
- Squamous cell carcinoma: Although unlikely, it is essential to rule out skin cancer, especially if the lesion is painful and has been present for an extended period.
- Genital herpes: Despite negative STD test results, it is crucial to consider genital herpes, as some cases may not be detected by standard tests.
- Syphilis: Another important consideration, as syphilis can cause a variety of skin lesions and may not always be detected by initial tests.
Rare Diagnoses
- Erythema multiforme: A rare skin condition that can cause target-like lesions, which may be painful and pruritic.
- Lichen planus: A chronic inflammatory skin condition that can cause lesions on the genital area, although it is relatively rare.
- Zoon's balanitis: A rare condition that causes a painful, erythematous lesion on the glans penis, often associated with chronic inflammation.