What is the differential diagnosis and treatment for a recurrent red lump on the gluteal area in a patient with a history of cat scratch disease (cat scratch fever) that resolved 3 years ago?

Recurrent Red Lump at Prior Cat Scratch Site: Differential Diagnosis and Treatment

This is most likely a recurrent localized inflammatory reaction (sterile abscess, foreign body granuloma, or suture granuloma) rather than active Bartonella henselae infection, given the 3-year interval and brief 2-3 day duration of episodes. 1

Differential Diagnosis

Most Likely Diagnoses

• Foreign body granuloma or retained material: The original infection may have left behind foreign material (hair, debris, suture material if drained previously) causing intermittent inflammatory flares 1
• Sterile abscess or inflammatory nodule: Recurrent inflammation at a previous infection site without active bacterial infection 1
• Epidermal inclusion cyst: Can develop at sites of prior trauma and become intermittently inflamed 1

Less Likely but Consider

• Recurrent bacterial abscess (non-Bartonella): Would typically require Staphylococcus aureus or Streptococcus coverage, though the brief 2-3 day duration and spontaneous resolution argue against this 1
• Hidradenitis suppurativa: Can present with recurrent nodules, though gluteal location is less typical 1
• Pilonidal disease: Relevant for gluteal/sacral location with recurrent inflammation 1

Unlikely Given Clinical Context

• Active Bartonella henselae infection: Cat scratch disease lymphadenopathy typically resolves within 1-6 months and does not recur years later with brief 2-3 day episodes 2, 3
• Cutaneous malignancy: Would not spontaneously resolve every 2-3 days 1

Diagnostic Workup

Initial Assessment

• Examine during an active flare: Document size, warmth, fluctuance, surrounding erythema, and any drainage 1
• Palpate for underlying mass or foreign body when lesion is quiescent 1
• Check for sinus tract or punctum suggesting foreign body or pilonidal disease 1

If Lesion Persists or Worsens

• Incision and drainage with culture if fluctuant during next episode to rule out bacterial abscess and identify any foreign material 1
• Excisional biopsy if a persistent nodule is palpable between flares to exclude foreign body granuloma, atypical infection, or neoplasm 1
• Do NOT perform Bartonella serology: This would not be helpful 3 years post-infection and does not explain the recurrent brief episodes 2, 3

Treatment Approach

For Intermittent 2-3 Day Flares (Current Presentation)

Observation is appropriate if episodes are brief, self-limited, and not progressively worsening 1

Conservative management during flares:

• Warm compresses to the area 1
• NSAIDs for symptomatic relief 1
• Avoid manipulation or squeezing 1

If Episodes Become More Frequent, Prolonged, or Symptomatic

Surgical excision is the definitive treatment for recurrent inflammatory lesions at prior infection sites 1

• Complete excision of the nodule/scar tissue with any foreign material 1
• Send specimen for histopathology and culture 1

Antibiotic Therapy is NOT Indicated Unless:

• Fluctuant abscess with surrounding cellulitis: Treat empirically for MRSA and Streptococcus with TMP-SMX plus cephalexin, or doxycycline, or clindamycin monotherapy 1
• Systemic signs of infection (fever, malaise): Broader coverage may be needed 1
• Culture-proven bacterial infection: Tailor antibiotics to sensitivities 1

Do NOT treat with azithromycin or doxycycline for presumed Bartonella: The 3-year interval and brief episodic nature make active cat scratch disease extremely unlikely 2, 4, 3

Key Clinical Pitfalls

• Avoid misdiagnosing as recurrent cat scratch disease: B. henselae lymphadenopathy does not present with brief 2-3 day recurrent episodes years after initial infection 2, 3
• Do not empirically treat with antibiotics: Most recurrent inflammatory nodules at prior infection sites are sterile and require excision, not antibiotics 1
• Ensure complete excision if surgery performed: Incomplete removal of foreign material or cyst wall leads to recurrence 1
• Consider imaging (ultrasound or MRI) before excision if concerned about deeper involvement or to identify foreign body 1