A 14-year-old girl presents with pain and decreased vision in her left eye. She
loves animals, and has three pets.
What is your diagnosis, what test(s) would you order to confirm your suspicions, and what treatment, if any, do you recommend?
DIAGNOSIS: Cat scratch disease (CSD) (Bartonellosis) with Leber's stellate neuroretinopathy.
There are 16 Bartonella species known or suspected to be human pathogens. B. henselae is the principle etiologic agent of CSD, with rare cases due to Afipia felis and other Bartonella species. Inoculation of B. henselae, possible by contaminated flea feces, usually results from a cat scratch or bite.
Of patients with CAD. 85-90% have typical disease. A primary lesion (a pustule or papule) develops at the innoculation site within days to two weeks in 1/3rd to 2/3rds of patients, with lympadenopathy developing within 1 to 3 weeks or longer after cat contact. The nodes are enlarged, painful, and suppurate in 10-15% of cases. Patients may have fever, anorexia, malaise, and weight loss.
Atypical (extranodal) CSD, which includes neuroretinitis, occurs in 10-15% of cases. Manifestations may include nervous sytem (encephalopathy, seizures, myelitis, radiculitis, cerebrellitis, cranial & peripheral nerve palsies), musculoskeletal (myalgia, arthritis), skin (erythema nodosum, erythema multiforme), lung (pneumonitis, pleural effusions), blood (ITP, Henoch-Schonlein purpura), heart (myocarditis, endocarditis), renal (glomerulonephritis), and fever of unknown origin.
Diagnosis of CSD is usually made by obtaining an acute and convalescent serum for an ELISA or immunofluorescence assay. PCR of pus aspirated from an infected node is a sensitive and highly specific method of diagnosis in seronegative individuals.
Treatment of typical CSD with extensive lymphadenopathy is azithromycin (500 mg PO on day 1, then 250 mg PO once a day for 4 days). For severe cases of neuroretinitis, doxycycline (100 mg PO bid) plus rifampin (300 mg PO bid) is given for 4-6 weeks (consider adding systemic glucocorticoids).