Differential Diagnosis

The patient's presentation of small papules along the balanopreputial sulcus, resembling pearly penile papules (PPP), along with a history of a reddish lesion that has not healed, suggests several potential diagnoses. The following categories outline the differential diagnoses:

• Single Most Likely Diagnosis
  • Pearly Penile Papules (PPP): The description of small papules along the balanopreputial sulcus, particularly on the right side near a visible vein, is highly suggestive of PPP. The fact that these papules resemble PPP and have appeared after an initial lesion, which was treated with various medications, supports this diagnosis. PPP is a benign condition and can cause intermittent itching, which is relieved by topical applications, as seen with Bepanthen in this case.
• Other Likely Diagnoses
  • Contact Dermatitis: Given the patient's history of wearing the same underwear for 3 consecutive days before the onset of symptoms, contact dermatitis is a plausible diagnosis. The initial reddish lesion and the subsequent development of papules could be related to an allergic or irritant reaction.
  • Eczema/Dermatitis: The dermatologist's suggestion of a form of dermatitis, combined with the patient's symptoms of itching (albeit intermittent and only on the right side), supports considering eczema or dermatitis as a differential diagnosis.
• Do Not Miss Diagnoses
  • Squamous Cell Carcinoma or Other Malignancies: Although the patient's lesions are non-painful and non-itchy, with no systemic symptoms, it is crucial not to miss potential malignancies, especially given the incomplete epithelial regeneration of the reddish area on the left. A biopsy might be necessary to rule out squamous cell carcinoma or other malignancies.
  • Sexually Transmitted Infections (STIs): Despite the patient's claim of no sexual activity, it is essential to consider STIs due to the potential for undisclosed or non-consensual sexual contact. Conditions like secondary syphilis can present with a variety of skin manifestations.
• Rare Diagnoses
  • Lichen Nitidus: This rare condition can present with small, shiny, flat-topped papules and could be considered given the patient's symptoms, although it is less likely.
  • Lichen Planus: Another rare condition that could present with papules and itching, although the distribution and description are not as typical for lichen planus.

Further Evaluation or Management

Given the differential diagnoses, further evaluation could include:

• A thorough sexual history, despite the patient's denial of sexual activity, to assess the risk for STIs.
• A biopsy of the reddish lesion on the left to rule out malignancy and to assess for any specific dermatological conditions.
• Patch testing to evaluate for contact dermatitis, especially if the patient has been exposed to new products or materials.
• Consideration of a trial of topical steroids for the management of potential dermatitis or eczema, under close supervision.
• Continued monitoring of the lesions for any changes in size, color, or symptoms, which could indicate a need for re-evaluation of the diagnosis.