Differential Diagnosis for Arthropod Bite

• Single most likely diagnosis
  • Insect bite reaction (e.g., mosquito, flea, or ant bites): This is the most common cause of arthropod bites and typically presents with localized itching, redness, and swelling.
• Other Likely diagnoses
  • Scabies: Caused by the mite Sarcoptes scabiei, scabies is a highly contagious skin infestation that presents with intense itching and characteristic burrows.
  • Bed bug bites: Cimex lectularius, the common bed bug, can cause bites that are often mistaken for other arthropod bites, presenting with linear or clustered itchy lesions.
  • Chigger bites: The larvae of trombiculid mites, chiggers can cause intense itching and small, raised lesions, often in areas where clothing fits tightly.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Tick-borne illnesses (e.g., Lyme disease, Rocky Mountain spotted fever): Although less common, tick bites can transmit serious diseases, making prompt recognition and treatment crucial.
  • Brown recluse spider bite: The venom from a brown recluse spider can cause necrotic lesions and systemic symptoms, requiring immediate medical attention.
  • Black widow spider bite: The neurotoxin from a black widow spider can cause severe pain, muscle cramps, and breathing difficulties, necessitating urgent care.
• Rare diagnoses
  • Tungiasis: Caused by the flea Tunga penetrans, tungiasis is a rare condition where the flea embeds itself in the skin, typically on the feet, causing lesions and discomfort.
  • Myiasis: A rare infestation where fly larvae feed on living tissue, myiasis can cause significant tissue damage and requires prompt treatment.
  • Leishmaniasis: Transmitted by the bite of an infected sand fly, leishmaniasis is a rare but serious disease that can cause skin lesions, organ damage, and death if left untreated.