Differential Diagnosis

The patient's presentation of a painful swelling in the left groin, associated with spreading redness, fever, and a history of similar episodes, suggests a range of possible diagnoses. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Cellulitis with possible underlying abscess or infected cyst: The patient's symptoms of a painful swelling, spreading redness, and fever are consistent with cellulitis, a common bacterial skin infection. The history of a similar episode on the same side suggests a possible underlying cause such as an infected cyst or abscess that has recurred.

• Other Likely Diagnoses

  • Lymphadenitis or infected lymph node: The groin swelling and redness could be due to an infected lymph node, which could be related to the patient's history of styes (which are infected eyelash follicles or meibomian glands) and could indicate a systemic or localized infection.
  • Thrombophlebitis or deep vein thrombosis (DVT): Although less likely given the patient's symptoms, thrombophlebitis or DVT could cause swelling and pain in the groin area, especially if the patient has been bedridden.
  • Erythema nodosum or other inflammatory conditions: The patient's rash and swelling could be indicative of an inflammatory condition such as erythema nodosum, which can be associated with various underlying causes including infections and autoimmune diseases.

• Do Not Miss Diagnoses

  • Necrotizing fasciitis: This is a life-threatening condition that requires immediate medical attention. Although less common, the patient's symptoms of spreading redness, fever, and severe pain could be indicative of necrotizing fasciitis, especially if the patient's condition rapidly deteriorates.
  • Septic thrombophlebitis: An infected thrombus in a vein could lead to sepsis, a potentially fatal condition if not promptly treated.
  • Malignancy (e.g., lymphoma): Although rare, a malignancy such as lymphoma could present with lymphadenopathy (swollen lymph nodes) and systemic symptoms like fever and rash.

• Rare Diagnoses

  • Hidradenitis suppurativa: A chronic skin condition that can cause painful swellings in the groin area, although it typically presents with recurrent abscesses and sinus tracts.
  • Granulomatosis with polyangiitis (formerly Wegener's granulomatosis): A rare autoimmune disorder that can cause a wide range of symptoms including skin lesions, fever, and eye inflammation, but it is much less likely given the patient's presentation.
  • Sweet syndrome (acute febrile neutrophilic dermatosis): Characterized by fever, leukocytosis, and tender, erythematous skin lesions, Sweet syndrome is a rare condition that could be considered in the differential diagnosis but is less likely.