Differential Diagnosis for 45-year-old Female with Facial Lesion

• Single most likely diagnosis
  • Furuncle or Carbuncle: The patient's presentation of a tender pimple-like lesion that progressed to a vesicular rash with increased redness, swelling, and a swollen lymph node under the chin is suggestive of a furuncle (boil) or carbuncle, which are infections of the hair follicle and surrounding tissue, typically caused by Staphylococcus aureus. The attempt to squeeze the lesion and the expression of clear discharge further support this diagnosis.
• Other Likely diagnoses
  • Impetigo: A contagious skin infection that can cause red sores, vesicles, and crusts, often accompanied by swollen lymph nodes. The initial presentation of a pimple-like lesion and the progression to a vesicular rash could be consistent with impetigo.
  • Folliculitis: An inflammation of the hair follicles, which can be caused by bacterial, viral, or fungal infections. The patient's symptoms of a tender lesion and vesicular rash could be indicative of folliculitis.
  • Contact Dermatitis: An allergic or irritant reaction to a substance that comes into contact with the skin, which could have been exacerbated by the application of Difren Gel. However, the presence of a swollen lymph node and the progression of the lesion make this less likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Ludwig's Angina: A severe infection of the tissues in the neck, which can cause swelling, pain, and difficulty swallowing. Although the patient's symptoms are currently localized to the chin, the presence of a swollen lymph node and increasing discomfort warrant consideration of this potentially life-threatening condition.
  • Erysipelas: A type of skin infection that can cause redness, swelling, and vesicles, often accompanied by systemic symptoms such as fever and malaise. If left untreated, erysipelas can lead to serious complications, including sepsis and organ failure.
• Rare diagnoses
  • Herpes Zoster (Shingles): A viral infection that can cause a painful rash, often accompanied by systemic symptoms such as fever and malaise. Although the patient's symptoms are currently localized to the chin, the presence of a vesicular rash could be suggestive of herpes zoster.
  • Dermatological manifestation of an underlying systemic disease (e.g., Lupus, Rheumatoid Arthritis): In some cases, skin lesions can be a manifestation of an underlying systemic disease. Although this is less likely given the patient's presentation, it should be considered in the differential diagnosis, especially if the patient has a history of autoimmune disorders or if the lesion does not respond to treatment.