Differential Diagnosis

The patient's symptoms of internal and external dysuria, tingling sensation, and a small erythematous lesion on the vulva suggest several possible diagnoses. Here is a categorized differential diagnosis:

• Single most likely diagnosis
  • Vulvovaginal candidiasis: This condition is characterized by itching, burning, and abnormal discharge, which could explain the patient's symptoms of internal and external dysuria and the erythematous lesion. The odor difference could also be consistent with a yeast infection.
• Other Likely diagnoses
  • Bacterial vaginosis: Although the primary symptom is an abnormal odor, some patients may experience dysuria and vulvar irritation, making this a plausible diagnosis.
  • Trichomoniasis: This sexually transmitted infection can cause dysuria, abnormal discharge, and vulvar lesions, fitting some of the patient's symptoms.
  • Contact dermatitis or irritant dermatitis: The erythematous lesion and tingling sensation could be due to an allergic reaction or irritation from soaps, douches, or other products.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Herpes simplex virus (HSV): Although less common, HSV can cause severe symptoms, including painful lesions and dysuria. Missing this diagnosis could lead to significant morbidity and potential for transmission.
  • Syphilis: The primary stage of syphilis can present with a single, painless chancre, but in some cases, it may be painful and accompanied by other symptoms like dysuria.
• Rare diagnoses
  • Lichen sclerosis: A chronic condition that can cause vulvar itching, burning, and white patches, potentially leading to dysuria and lesions.
  • Vulvar intraepithelial neoplasia or cancer: Although rare, these conditions can present with vulvar lesions and symptoms like dysuria, making them important to consider in the differential diagnosis.