Granulomatous nodule(s) on the palpebral and bulbar conjunctiva; visibly swollen ipsilateral preauricular or submandibular lymph nodes.
Cat-scratch disease from Bartonella henselae (most common cause): Often a history of being scratched or licked by a kitten within 2 weeks of symptom onset.
Tularemia: History of contact with rabbits, other small wild animals, or ticks. Patients have severe headache, fever, and other systemic manifestations.
Rare causes: Syphilis, leukemia, lymphoma, mumps, Epstein–Barr virus, HSV, fungi, sarcoidosis, listeria, typhus, and others.
Initiated when etiology is unknown (e.g., no recent cat scratch). Consider:
Conjunctival biopsy with scrapings for Gram, Giemsa, and acid-fast stains.
Conjunctival cultures on blood, Löwenstein–Jensen, Sabouraud, and thioglycolate media.
Complete blood count, rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL), fluorescent treponemal antibody absorption (FTA-ABS) or treponemal-specific assay (e.g., microhemagglutination assay for Treponema pallidum [MHA-TP]), angiotensin-converting enzyme (ACE), and, if the patient is febrile, blood cultures.
Chest x-ray, purified protein derivative (PPD) of tuberculin, and/or interferon-gamma release assay (IGRA, QuantiFERON-TB Gold).
If diagnosis of cat-scratch disease is uncertain, then cat-scratch serology and cat-scratch skin test (Hanger–Rose) can be performed.
Cat-scratch disease: Generally resolves spontaneously in 6 weeks. Consider azithromycin 500 mg p.o. q.i.d., then 250 mg daily for four doses (for children, 10 mg/kg q.i.d., then 5 mg/kg daily for four doses); alternatives include trimethoprim/sulfamethoxazole (160/800 mg b.i.d.) or ciprofloxacin 500 mg p.o. b.i.d. Duration should be individualized based on severity and response to treatment. Use a topical antibiotic (e.g., bacitracin/polymyxin B ointment or gentamicin drops q.i.d.). The cat does not need to be removed.
Tularemia: Recommended therapy is gentamicin 5mg/kg once daily i.m. or i.v. for 10 days. For mild illness, alternative therapies include ciprofloxacin 500 mg p.o. b.i.d. for 10 to 14 days or doxycycline 100 mg p.o. b.i.d. for 14 to 21 days. Systemic medication should coincide with gentamicin 0.3% drops q2h for 1 week and then five times per day until resolved. Often patients are systemically ill and under the care of a medical internist for tularemia; if not, refer to a medical internist for systemic management.
Tuberculosis: Refer to an internist for antituberculosis medication.
Syphilis: Systemic penicillin (dose and route depend on the stage of syphilis) and topical tetracycline ointment (see 12.10, Syphilis).