Differential Diagnosis for Neutrophilic Infection in the Cap

• Single Most Likely Diagnosis
  • Staphylococcus aureus: This bacterium is a common cause of neutrophilic infections, particularly in the skin and soft tissues, including the scalp (cap). It can lead to conditions like folliculitis, furuncles, and carbuncles, which are characterized by significant neutrophilic infiltration.
• Other Likely Diagnoses
  • Streptococcus pyogenes: Known for causing skin infections, this bacterium can lead to conditions such as impetigo, which may present with neutrophilic infiltration, especially in the context of a secondary infection.
  • Pseudomonas aeruginosa: Though less common, Pseudomonas can cause infections in the scalp, particularly in immunocompromised individuals or those with significant exposure to water (e.g., swimmers), leading to conditions like folliculitis.
• Do Not Miss Diagnoses
  • Meningococcus (Neisseria meningitidis): Although rare, meningococcal infections can present with skin manifestations, including a rash that might initially resemble a neutrophilic infection of the scalp. Given its potential for severe and rapid progression to meningitis or sepsis, it's crucial not to miss this diagnosis.
  • Haemophilus influenzae: This bacterium can cause infections in various parts of the body, including the scalp, especially in children. It's essential to consider, especially if there's a suspicion of a more severe infection like meningitis or sepsis.
• Rare Diagnoses
  • Klebsiella pneumoniae: While more commonly associated with pneumonia, Klebsiella can cause skin and soft tissue infections, including those in the scalp, particularly in immunocompromised patients or those with specific risk factors.
  • Eikenella corrodens: This bacterium can cause infections, often in the context of human bites or clenched-fist injuries, and might rarely be involved in scalp infections, particularly if there's a history of trauma.