Cat scratch disease
|Cat scratch disease|
|Classification and external resources|
Cat-scratch disease (CSD) is an infectious disease consisting of gradually progressive regional lymphadenopathy, often occurring after contact with a feline animal (often a scratch). Atypical presentations are characterized by a variety of neurologic manifestations as well as granulomatous involvement of the eye, liver, spleen, and bone. The disease is usually self-limiting, and recovery is typically complete; however, patients with atypical presentations, especially if immunocompromised, may suffer significant morbidity and even mortality.
- 1 Disease
- 2 Etiology
- 3 General Pathology
- 4 Pathophysiology
- 5 Diagnosis
- 6 Management
- 7 Additional Resources
- 8 References
There are generally two forms of CSD as it relates to the eye:
- Parinauds Ocularglanduar Syndrome: consisting mostly of lymphadenopathy and follicular conjunctivitis
- Neuroretinitis due to Cat scratch disease: consisting mostly of lymphadenopathy and granulomatous inflammation of the retina and optic nerve with classic optic nerve swelling and macular star (neuroretinitis), and possible vasculitis.
Major cause: Bartonella henselae, possibly Afipia felis and Bartonella clarrigeiae. To be clear, there are other causes of neuroretinitis which would not be strictly considered CSD. The definition of CSD is based on the organism primarily, in combination with the presenting findings.
Bartonella species are a gram-negative bacillus that has been associated with a clinical syndrome of a self-limited lymphadenopathy associated with a cat scratch or bite or transmission through vectors such as fleas or flies. Mode of transmission: predominantly by direct inoculation through the scratch, bite, or lick of a cat, especially a kitten.
Bartonella organisms typically invade, and colonize mature erythrocytes. However, endothelial cells are also a target for Bartonella organisms, and appear to be the target host cells in humans. Endothelial invasion leads to a pro-inflammatory response and vasoproliferation.
Diagnosis of CSD is straight forward in the presence of typical neuroretinitis, and macular star formation, in addition to labratory testing pointing to Bartonella infection (typically blood test/titers) Additionally, recognition of isolated discrete white retinal, and chorioretinal lesions may aid in diagnosis.
Approximately 1-3 weeks after inoculation of the bacteria into the host, regional lymphatic tissues begin to display granulomatous infiltration associated with gradual hypertrophy.
The most common presentation is regional lymphadenopathy. Pre-auricular, submandibular, or cervical lymph nodes are typically affected. Conjunctival epithelium ulcerations, and necrosis are commonly seen producing a purulent discharge in severe cases. Erythematous overlying skin, showing signs of suppuration from involved lymph nodes. Careful examination; evidence of cutaneous inoculation in the form of a nonpruritic, slightly tender pustule or papule.
Typical ocular presentation includes neuroretinitis with macular star formation, and discrete white retinal or choroidal lesions. Vascular leakage from the optic nerve head results in the macular star formation, which may persist for months despite resolution of the neuroretinitis. In more recent studies, discrete white retinal, and chorioretinal lesions were a more common finding than the ‘classic’ macular star, and neuroretinitis. Additionally, an afferent pupillary defect is typically present in unilateral cases, and a cecocentral scotoma is present on visual field testing. More sight-threatening presentation includes retinal vasculitis, and vascular occlusions. Less common posterior segment findings include Branch retinal artery, and vein occlusion, and local serous retinal detachments.
Parinaud oculoglandular syndrome (conjunctival inflammation with preauricular adenopathy) may be seen in about 7% of patients with cat-scratch disease.
Patients typically present with unilateral decline in vision (20/80) with systemic symptoms present in 67%. Unilateral conjunctiva injection, foreign body sensation, and epiphora. Malaise and headache in fewer than one third of patients.
Typical history of prodromal symptoms, lymphadenopathy, and cat exposure helps strengthen the diagnosis, especially when presenting in young adults or children.
Visual field testing sometimes shows cecocentral scotoma. Fluorescine angiography often shows optic nerve leakage.
Although rarely required, in the presence of typical presentation and blood titer, lymph node biopsy or culture may be performed.
- Biopsy: classically shows granulomatous inflammation. Warthin-Starry silver stain on biopsy can identify the bacteria.
- Culture: B. henselae is a fastidious, slow-growing, gram-negative rod that requires specific culture techniques for tissue or blood.
Serologies: An IFA or EIA Bartonella serology (titer ≥1:64) is diagnostic, with sensitivity, and specificity of 62%, and 100% respectively. A PCR assay on tissue or blood is also available.
Routine laboratory findings: Mild leukocytosis or leukopenia, infrequent eosinophilia and elevated ESR or CRP. Abnormalities of bilirubin excretion and elevated hepatic transaminases are usually secondary to hepatic obstruction by granuloma, mass, or lymph node. In patients with neurologic manifestations, lumbar puncture usually reveals normal CSF, although there may be a mild pleocytosis and modest elevation in protein.
Etiologies that must be differentiated include other causes of optic nerve head swelling such as optic neuritis, and sarcoid papillitis. Also, infectious etiologies such as syphilitic perineuritis, and rarely toxoplasmosis can produce a similar clinical appearance. Pseudotumor cerebri can mimic the less frequent appearance of bilateral CSD. Lyme disease, Rocky Mountain Spotted Fever, toxoplasmosis, toxocariasis, histoplasmosis, and leptospirosis may also cause neuroretinitis.
Granulomas of this syndrome must be differentiated from those associated with:
- Tuberculosis or other myobacterial infections
- Sporotrichosis or other fungal diseases
- Lymphogranuloma venereum
- Benign and malignant tumors such as lymphoma
CSD tends to be a self-limiting disease. Usually no treatment is recommended. However, patients with severe ocular or systemic complications, a course of antibiotics may be initiated. In immunocompromised patients, antibiotic treatment has lead to dramatic clinical responses
Antipyretics and NSAIDs may also be used. Warm compresses to the affected nodes. In cases of encephalitis or coma, antibiotics and supportive care are indicated.
Doxycycline (100 mg twice daily) has good intraocular, and central nervous system penetration. However, in patients less than 12 years of age, erythromycin is recommended due to the risk of tooth discoloration. Azithromycin has been observed to cause rapid resolution of lymphadenopathy. However, the distribution of azithromycin to the eye appears higher for conjunctival tissue but lower in intraocular fluids.
The visual prognosis is good with or without treatment.
- American Academy of Ophthalmology. Retina/Vitreous: Cat scratch disease Practicing Ophthalmologists Learning System, 2017 - 2019 San Francisco: American Academy of Ophthalmology, 2017.
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