Differential Diagnosis for Raised Skin Bumps

When considering the differential diagnosis for raised skin bumps that could be mistaken for bug bites or scabies, it's essential to approach the diagnosis systematically. Here's a categorized list to help guide the thought process:

• Single Most Likely Diagnosis

  • Insect bites (e.g., mosquitoes, fleas, bed bugs): This is often the most common cause of raised skin bumps, especially if the patient reports recent outdoor activities or exposure to pets. The bites typically present as pruritic, erythematous papules.

• Other Likely Diagnoses

  • Scabies: Caused by the mite Sarcoptes scabiei, scabies presents with intense itching, especially at night, and characteristic burrows in the skin. It's highly contagious and can affect anyone.
  • Contact dermatitis: This is a skin reaction that occurs after contact with an irritant or allergen, leading to red, itchy, and sometimes blistered skin.
  • Eczema (atopic dermatitis): A chronic condition characterized by dry, itchy, and inflamed skin, often appearing as red, raised patches.
  • Folliculitis: An inflammation of the hair follicles, usually caused by bacterial infection, which can present as small, itchy, red bumps.

• Do Not Miss Diagnoses

  • Cellulitis: A bacterial skin infection that can start as a small, red bump but quickly spreads, becoming a serious condition requiring immediate antibiotic treatment.
  • Methicillin-resistant Staphylococcus aureus (MRSA) skin infections: These can start as small bumps but can rapidly progress to abscesses or more severe infections.
  • Lyme disease: Although less common, the initial stage of Lyme disease can present with a characteristic "bull's-eye" rash (erythema migrans), which might be mistaken for a bug bite.

• Rare Diagnoses

  • Leishmaniasis: A parasitic disease spread by sandflies, which can cause skin lesions that might resemble bug bites.
  • Cutaneous larva migrans: Caused by the larvae of certain nematodes, this condition presents as a creeping eruption on the skin, often acquired through walking barefoot on contaminated soil.
  • Erythema multiforme: A skin condition characterized by target lesions, which can be triggered by infections or medications, and might be confused with severe bug bite reactions.

Each of these diagnoses has distinct features and risk factors. A thorough history, including travel, exposure to pets or outdoors, and the presence of systemic symptoms, along with a physical examination, is crucial for making an accurate diagnosis.