Cat Scratch Disease: Causes, Signs & Symptoms, Pathophysiology, Diagnosis & Treatment

cat scratch disease also known as cat scratch fever or subacute regional lymphadenitis is a bacterial infection affecting the regional lymph nodes proximal to the site of inoculation of bacteria bartonella henseli a gram negative bacillus is the major causative agent of cat scratch disease it is one of the most common causes of lymphadenopathy in children people with cat scratch disease usually have a history of sustaining a cat scratch or bite prior to the development of lymphadenopathy first let's discuss about the signs and symptoms of cat scratch disease more than 90 percent of patients with cat scratch disease develop one or more red brown non-tender papules at the site of inoculation of bacteria they usually appear within three to ten days after the bacteria are introduced and last for about one to three weeks they gradually resolve as lymphadenopathy appears within one to three weeks lymphadenopathy develops on a single node or a group of nodes draining the inoculation site in this picture the blue arrow indicates the primary site of inoculation of bacteria and the black circle indicates the adjacent lymphatinopathy single node involvement is more common lymph nodes of the neck and axially are frequently affected and involvement of inguinal lymph nodes is less common lymphadenopathy can be moderately tender with increased warmth of the overlying skin lymphadenopathy remains regional and typically resolves within two to four months however in some individuals it may take up to six months or even a year about 10 to 30 percent of nodes become supportive requiring needle aspiration approximately 50 percent of patients experience systemic symptoms including fever anorexia fatigue headache arthralgia and sore throat a typical cat scratch disease occurs in approximately 10 percent of patients clinical manifestations of a typical cat scratch disease include paranodicular glandular syndrome central nervous system involvement hepatosplenic cat scratch disease endocrine dietitis osteomyelitis and dermatologic manifestations paranodicula glandular syndrome is characterized by unilateral conjunctivitis with adjacent pre-auricular lymphadenopathy sometimes an ocular granuloma is also present in these patients the site of inoculation is the conjunctiva or eyelid secondary to a lick scratch or bite subsequent rubbing of the eye often leads to spreading these physical findings of atypical cat scratch disease usually resolve within a few months without leaving any residual damage central nervous system involvement can be seen in about five percent of patients common findings include encephalitis mental status changes seizures transient peripheral neuropathy mellitus and retinitis encephalitis is the commonest cns manifestation and is characterized by confusion restlessness and disorientation and rarely it may progress into coma sometimes seizures may progress into status epilepticus these features of cns involvement are typically self-limited however recovery takes a longer time compared to other manifestations of cat scratch disease hepatosplenic csd is a rare form of atypical cat scratch disease individuals present with fever without any identifiable cause physical examination findings of these patients are usually normal occasionally well-heeled cutaneous scars of cat scratches can be detected patients often complain of abdominal pain and discomfort lymphatinopathy presents only in about 50 percent of cases it is important to note that hepatosplenomegaly jaundice and elevated liver enzyme levels are not associated with this condition fever typically abates within 48 hours of antibiotic treatment bartonella species account for about 3 percent of all cases of endocarditis and patients with bartonella endocarditis often require valve replacement dermatologic manifestations occur in approximately five percent of patients and with more severe disease patients may present with multiple patecchial rashes on the skin however other organs can also be affected these dermatologic manifestations typically resolve within a few days cats scratch disease in immunocompromised patients is somewhat different from that in immunocompetent hosts normally benign disease of csd can be life-threatening to an immunocompromised host patients with hiv infection patients with cancer and patients who have undergone transplantations are all at risk these people develop bacillary angiomatosis bacillary polyesis or persistent or relapsing fever with bacteremia bacillary angiomatosis is a vascular proliferative disorder which is characterized by numerous red brown tumors of the skin and subcutaneous tissue without antibiotic therapy the disease progresses with dissemination bacillary poliosis involves the solid organs with reticulo endothelial elements such as liver spleen abdominal lymph nodes and bone marrow vascular proliferation of hepatic sinusoidal capillaries results in blood-filled spaces in the liver as you can see in the picture above now let's discuss a bit about the pathophysiology of cat scratch disease as mentioned earlier most cases of cat scratch disease are caused by bartonella henseli which is a small pleomorphic fastidious gram-negative intracellular bzillus infection with bartonella henseli gives a lifelong immunity to cat scratch disease domestic cats are the natural reservoir of bartonella henseli in cats however bartonella infection is asymptomatic fleas are believed to be transmitting the disease between cats transmission from cats to human occurs via a scratch or bite when the bacterium presence in cat's claws or oral cavity more than 90 of patients will report a history of contact with a cat typically a kitten the hallmark pathophysiologic feature of cat scratch disease is regional lymphadenopathy proximal to the site of inoculation of bacteria in immunocompetent patients bartonella infection causes a granulomatous and suppurative response lymph nodes become enlarged lymphoid hyperplasia and arteriolar proliferation can be seen early in the disease as the disease progresses granulomas appear with central necrosis an immune immunocompromised patients the response can be vascular proliferative with neovascularization bartonella contains a protein called adecinae which promotes vascular proliferation cat scratch disease is diagnosed when the patient presents with compatible signs and symptoms with a history of a cat scratch or bite serology can confirm the diagnosis by detection of serum antibodies against bartonella henseli lymph node aspiration is usually not recommended except to relieve pain and swelling or in cases where the diagnosis is unclear bartonella hensarly dna may be detected by pcr or culture of lymph node aspirates or blood however the sensitivity is not optimal when blood is used as bartonella hensely grows very slowly cultures should be held for a maximum of 21 days here is a microscopic image of bartonella henseli finally let's discuss about the treatment of cat scratch disease most cases of csd typically resolve without any treatment however some patients may develop complications from disseminated disease azithromycin has been shown to effective in decreasing lymph node volume more rapidly compared to no treatment many other types of antibiotics are also effective against bartonella species including penicillins tetracyclines cephalosporins and aminoglycosides with serious infection more than one antibiotic is used okay that's all i wish to discuss in this video hope you have learned something from it if you have any question or doubt regarding this topic feel free to post them in the comment section thanks for watching see you soon in the next video