Cat Scratch Disease

Eight-five percent to 90% of children have a self-limited lymphadenopathy accompanied by high fever. Patients with disseminated illness may have a spectrum of complications especially in the very young, elderly and immunocompromised host such as the transplant or HIV patient. Involved Systems may include the cutaneous, lymphatic and visceral organs. More uncommonly there may be ocular and neurologic involvement.

Cutaneous manifestations begin as an erythematous papule, vesicle or nodule which is known as the primary inoculation lesion. This lesion usually persists from one to three weeks but can last for months. The primary inoculation site may be a mucous membrane such as the conjunctiva that heals without scarring and is not detected. Examination of intertriginous areas, other skin creases as well as the scalp may help demonstrate the primary lesion.

Lymphatic system involvement presents as a tender lymphadenopathy, regional and may be solitary or multiple nodes 1 to 5 cm in diameter. There is overlying erythema. Ten percent may suppurate. The lymph nodes are enlarged proximal to the inoculation site. Common sites are the axillary, epitrochlear, cervical, supraclavicular, or submandibular lymph nodes. The lymphadenopathy may last from 1 to 4 months.

Visceral organ involvement may include the liver, spleen or both and present with fever, weight loss, and abdominal pain. There may be elevated acute phase reactants and liver function tests. Cat Scratch disease may be the cause of up to one-third of children with fever of unknown origin. 

Ophthalmic complications include neuroretinitis, papillitis, optic neuritis, and most commonly Parinaud Oculoglandular syndrome. This is an atypical presentation found in 2% to 8% percent of children which involves an inoculation site in the conjunctiva. There is local adenopathy typically preauricular, upper cervical or submandibular with severe conjunctival infection. The conjunctival infection resolves in several weeks, but the lymphadenopathy may persist for months. Cat scratch may also cause a focal or multifocal retinochoroiditis, panuveitis, branch retinal artery and vein occlusion, leading to retinal detachment.

Neurologic complications of Cat Scratch include ataxia, cranial nerve palsies, and a dementia-like picture in the elderly. Children typically present with encephalitis or aseptic meningitis. However, status epilepticus has been reported. 

A myriad of musculoskeletal complaints has been associated with Cat Scratch disease including arthralgias, myalgias, and frank arthritis.

There may be a presumptive diagnosis of Cat Scratch disease given the correct historical and examination findings. B. hensalae is difficult to culture. Exposure to cats is usually necessary for diagnosis. Serologic testing may confirm the diagnosis with EIA or IFA; however, negative serologic tests do not rule out the diagnosis. Lymph node biopsy is not indicated routinely but should be considered if the diagnosis is unclear. Historically, excision of affected lymph nodes has been avoided for fear of development of fistulas. Ultrasound may aid needle aspiration to obtain tissue.[8][9]

In mild cases, treatment may not be necessary. Supportive care including antipyretics and anti-inflammatory medications in addition to warm compresses to the inoculation site may be all that is needed. In mild to moderate presentation in immunocompetent patients, a course of azithromycin may be indicated. Zithromax for 5 days has been shown to relieve the pain of severe lymphadenopathy but shown no reduction in the overall duration of symptoms. Azithromycin dose is 10 mg/kg day 1 and 5 mg/kg days 2 to 5. Individuals weighing greater or equal to 45 kg can receive the adult (maximum) dose of 500 mg day one and 250 mg day 2 through 5. Immunocompromised patients should be treated to help prevent the progression to severe systemic disease. Antibiotic regimens including rifampin, trimethoprim-sulfisoxazole, and ciprofloxacin are available for severe, disseminated disease.[7][10][11]

Differential diagnosis includes causes of acute, subacute and chronic lymphadenopathy. The differential does include viral agents such as CMV, HIV, and EBV but these agents usually cause diffuse lymphadenopathy. Skin papules similar to the lesion at the inoculation site may occur in fungal infections, leishmaniasis, and nocardiasis. In immunocompromised hosts, there may be a myriad of infectious agents to consider. The presentations of HIV as bacillary angiomatosis may be confused with Kaposi's sarcoma.

In 90% to 95% of children, Cat Scratch disease will resolve spontaneously with symptomatic control including analgesics, antipyretics, and warm compresses. In patients with disseminated disease, recovery may take months to a year with morbidities depending on the system involved. The immunocompromised host may have a debilitating course.

Cat Scratch disease is a common cause of lymphadenopathy particular in the pediatric population. A thorough history and physical examination, as well as a high index of suspicion, will aid in the diagnosis. The course may be benign or severe and protracted. The age of the patient and comorbidities should be considered in the evaluation and treatment of the affected individual. Prevention of the disease requires adequate flea control and supervision of children around young cats.

Cat scratch disease is not uncommon in North America. The majority of patients present to the emergency room and because of its varied presentation, the disorder is best diagnosed and managed by an interprofessional team that includes an infectious disease expert, neurologist, surgeon ophthalmologist, and an internist. The outcomes for immunocompetent patients with cat scratch disease is excellent. However, those who have involvement of the peripheral or central nervous system may develop some type of neurological deficit that may persist after treatment. Death in immunocompetent patients is rare. The lymphadenitis often takes several months to resolve but most patients develop lifelong immunity to the infection. The prognosis in patients who are immunocompromised is guarded.[12][13] (level V)