Differential Diagnosis for Nikolsky Positive Lesions

The patient presents with Nikolsky positive lesions on the arms, is 87 years old, and has recently started Hydrochlorothiazide (HCTZ). Considering these factors, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Drug-induced pemphigus: The recent initiation of HCTZ, a known culprit in drug-induced pemphigus, combined with the Nikolsky positive lesions, makes this a highly plausible diagnosis. Pemphigus is an autoimmune disease characterized by blistering of the skin and mucous membranes, and certain drugs like HCTZ can trigger it.

• Other Likely Diagnoses

  • Bullous pemphigoid: Although less directly linked to HCTZ, bullous pemphigoid is another autoimmune blistering disease that could present with Nikolsky positive lesions, especially in an elderly patient.
  • Staphylococcal scalded skin syndrome (SSSS): While more common in children, SSSS can occur in adults, especially those with compromised immune systems or renal failure, and could potentially present with Nikolsky positive lesions.
  • Toxic epidermal necrolysis (TEN): Given the patient's recent start of a new medication, TEN, a severe skin condition usually triggered by medications, should be considered, although it typically involves more widespread skin detachment.

• Do Not Miss Diagnoses

  • Steven-Johnson Syndrome (SJS): A severe form of skin and mucous membrane disorder, usually a reaction to medication or infection. It's crucial to identify SJS early due to its high morbidity and mortality.
  • Paraneoplastic pemphigus: A rare autoimmune disorder associated with underlying neoplasia, which can present with severe blistering skin disease and is often resistant to treatment.
  • Infectious causes (e.g., impetigo, ecthyma): Certain bacterial infections can cause skin lesions that might be Nikolsky positive, and while less likely, missing an infectious cause could lead to significant morbidity.

• Rare Diagnoses

  • Epidermolysis bullosa acquisita (EBA): A rare autoimmune disease characterized by blistering of the skin, which could potentially present with Nikolsky positive lesions.
  • Linear IgA bullous dermatosis: An autoimmune skin disorder characterized by blistering, which could be considered in the differential diagnosis of Nikolsky positive lesions, especially if other causes are ruled out.
  • Dermatitis herpetiformis: An autoimmune skin condition characterized by intensely itchy blisters, which, although less likely, could be a consideration in a differential diagnosis of blistering skin diseases.