A 19-year-old man with no history of chronic diseases presented with an enlarged axillary lymph node on the right side, accompanied by night sweats and body temperature of up to 38 °C. A few days after the symptom onset, a partial resolution was observed—fever and night sweats subsided.

Two weeks later, due to persistent lymphadenitis, the patient consulted a family doctor and was treated with amoxicillin combined with clavulanic acid, without further improvement. Another 2 weeks later, he reported worsening of the symptoms—the lymph node had enlarged again. At this point, he was referred to an infectious diseases clinic.

Physical examination showed a painful cluster of lymph nodes in the right axilla, with no fistula, but with slight redness of the skin overlying the nodes. The patient reported owning a cat and having been scratched by the animal multiple times over the past 6 months.

Laboratory workup showed a leukocyte count of 11 500 cells/μl (reference range [RR], 4000–10 000 cells/μl, with neutrophil predominance, and a C-reactive protein level of 52 mg/l (RR <⁠5 mg/l). Antibiotic treatment with azithromycin was initiated due to suspected cat scratch disease. After 2 days of treatment, the patient noticed partial improvement, and the lymph node slightly decreased in size. A Bartonella immunoglobulin M (IgM) test was performed (the B. henselae VirClia IgM monotest, Vircell S.L., Granada, Spain, with 92% sensitivity and 91% specificity), yielding a positive result. Stepwise diagnostic pathway is presented in Figure 1.

Figure 1. Differential diagnostic pathway in a 19-year-old man with unilateral axillary lymphadenopathy

Abbreviations: EBV, Epstein–Barr virus; ID, infectious diseases; Ig, immunoglobulin

After another 2 days, due to increasing skin redness and pain in the affected area, the patient was evaluated by a surgeon. An incision of the skin over the affected area was performed, resulting in discharge of purulent material. Following surgical treatment, the patient experienced symptom resolution and continued follow-up at the local infectious diseases outpatient clinic.

The causative agent of cat scratch disease is B. henselae, a gram-negative, nonmotile, intracellular rod.1 It is transmitted through a scratch, bite, or lick by an infected cat, or, in rare cases, through contact with cat flea excrement on mucous membranes of broken skin.2

Most cases occur in children and young adults. Symptoms include a papule at the inoculation site followed by local lymphadenopathy in the corresponding region 1–3 weeks later. The most commonly affected lymph nodes are axillary, cervical, and inguinal. They are tender on palpation, and the overlying skin is erythematous. On histological examination, granulomas, necrosis, and multiple coalescing microabscesses are typically seen.3 Lymphadenopathy can be accompanied by fever, malaise, and myalgia.2 In immunocompetent hosts, the disease is usually self-limiting withing weeks to months, but it has also been identified as a relatively common cause of fever of unknown origin.1,3 In immunosuppressed individuals, the disease may have a more severe course with systemic involvement.3

The diagnosis can be confirmed by fairly accurate serological tests. However, negative results do not exclude cat scratch disease, which should always be considered in the differential diagnosis of lymphadenopathy when clinical presentation and a history of cat exposure are consistent.1

Suppuration of lymphadenopathy has been reported in 10%–40% of the cases. It carries a risk of fistula formation and requires needle aspiration or surgical incision. It can be present in immunocompetent patients despite appropriate treatment.2,4

Our patient showed a typical course of the disease. This case emphasizes that cat scratch disease should be considered in the diagnostic evaluation of lymphadenitis.