Differential Diagnosis

The patient's symptoms of light spots on the skin that do not tan, following a 6-month course of antibiotics, suggest several potential diagnoses. These can be categorized as follows:

• Single most likely diagnosis

  • Vitiligo: This condition is characterized by the loss of skin pigment cells (melanocytes), leading to white patches on the skin. The onset after a prolonged antibiotic course could be coincidental, but stress and certain medications can sometimes trigger or exacerbate vitiligo.

• Other Likely diagnoses

  • Pityriasis versicolor (also known as tinea versicolor): A common skin condition caused by an overgrowth of yeast on the skin, leading to patches that are lighter or darker than the surrounding skin. Antibiotics can alter the skin's microbiome, potentially leading to this condition.
  • Post-inflammatory hypopigmentation: Certain skin conditions or reactions can lead to areas of the skin becoming lighter due to inflammation. The antibiotics could have caused a skin reaction in some individuals.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Sarcoidosis: A condition that can cause skin lesions and patches, among other systemic symptoms. While less common, it's crucial to consider due to its potential for serious complications if left untreated.
  • Leprosy (Hansen's disease): A chronic bacterial infection that can cause light-colored skin patches, among other symptoms. Although rare in many parts of the world, it's essential to consider, especially if the patient has traveled to or lives in an endemic area.

• Rare diagnoses

  • Idiopathic guttate hypomelanosis: A condition characterized by small, discrete, hypopigmented macules, often on the extremities. It's more common in older adults but can occur at any age.
  • Chemical or drug-induced leukoderma: Certain chemicals or drugs can cause skin depigmentation. While antibiotics are less commonly associated with this, it's a possibility, especially with prolonged use.