Cat Scratch Disease: A Familial Disease?

Introduction

Approximately 22 000 cases of cat scratch disease (CSD) are diagnosed annually in the United States. ¹ Cat scratch disease is caused by the fastidious, gram-negative bacillus Bartonella henselae. Children 5 to 9 years of age have the highest incidence of CSD. ² Cat scratch disease occurs via inoculation through scratch, lick, or bite from a bacteremic cat. ² Kittens, 12 months or younger, are more likely to be bacteremic than older cats.^2,3

Cat scratch disease does not typically present as clusters or among multiple family members.^4,5 This case report focuses on 3 children within a family unit who were diagnosed with CSD. Diagnosis of the first child assisted providers in prompt recognition and treatment of CSD in other family members.

Case 1

A 7-year-old male with no significant past medical history presented to clinic with concern for a left inguinal mass. Family noticed the mass 2 days prior to presentation, as well as purulent yellow-green drainage from a wound on the left foot. There was no known trauma or injury to the area. There was a history of 1 week of intermittent fever and left groin pain. Fever had been previously evaluated at an urgent care clinic, where point-of-care tests were negative for influenza, mononucleosis, and strep throat. He was prescribed amoxicillin due to a concern for pharyngitis. Family had older outdoor cats and dogs, but no kittens. History was negative for any known or reported cat bite or scratch.

At this initial presentation, physical examination was notable for a swollen, erythematous 4 by 3 cm left inguinal lymph node which was tender to palpation. There was no hepatosplenomegaly, joint swelling, or joint pain. An open wound was present between the left 4th and 5th toes. No erythema or purulent drainage was present. A diagnosis of lymphadenitis secondary to wound infection on his foot was made, and treatment with intramuscular ceftriaxone was given. Amoxicillin was discontinued. He was re-evaluated in clinic the next day. Fever resolved, and the swelling had improved. He was given a second dose of ceftriaxone, and 7-day cefalexin course was prescribed. Five days after initial evaluation, the child presented to the emergency department (ED) with recurrent swelling and tenderness in the left groin, as well as low-grade fever. Toe wound was noted to be healing. Ultrasound showed a prominent enlarged left inguinal lymph node (4.1 by 1.9 by 3.6 cm). Laboratory work was obtained: white blood cell (WBC) 12 200/mm³, hemoglobin 12.6 g/dL, C-reactive protein (CRP) mildly elevated 15.61 mg/L, and B henselae serologic tests collected. A 5-day course of azithromycin was prescribed. Patient was discharged home to complete the azithromycin and cefalexin course.

Approximately 1 week later, patient returned to clinic due to worsening swelling and pain, affecting gait. Bartonella henselae serologic tests from the initial ED visit were IgM positive (1:64) and IgG positive (>1:1024). Family recalled that there was kitten exposure in the previous month. A 10-day course of clindamycin and a second 5-day course of azithromycin were prescribed. Despite antibiotics, the child developed fever within 4 days, prompting hospital admission for intravenous clindamycin and a surgical consult. A computed tomography (CT) scan showed a left inguinal abscess (2.8 by 1.2 by 1.9 cm). Laboratory work obtained included the following: WBC 11 000/mm³, hemoglobin 11.9 g/dL, CRP 20.06 mg/L, procalcitonin 0.04 ng/mL, and COVID negative. Incision and drainage (I&D) was performed with 40 cc of purulent output. Aerobic, anaerobic, acid fast bacillus, and fungal cultures were obtained and resulted in no growth. Patient recovered well after the I&D and was discharged home to complete the clindamycin course.

Within a week after I&D, patient developed new left inguinal swelling. Repeat I&D was performed for 2 new left inguinal abscesses, after confirmation by ultrasound. 100 cc of purulent material was drained. Vessel loops were placed by surgical team for patency between the 3 I&D sites. Vessel loops were removed the following week. Patient recovered well.

Case 2

A 7-year-old male, stepbrother of case 1, with history of asthma presented to the clinic for evaluation of 2 days right inguinal mass. He had 1 day of fever a week prior. History was positive for scratch by kittens. Examination was notable for a mobile, tender right inguinal lymph node, 1 by 2 cm in size. There was also a small 0.5 cm mobile, nontender left axillary lymph node. The family’s outdoor cats recently had kittens, which the children play with. During evaluation, the primary care pediatrician recalled stepbrother’s diagnosis of CSD from 2 years prior (case 1). A 5-day course of azithromycin was prescribed. At follow-ups, axillary lymphadenopathy resolved, whereas right inguinal lymph node continued to reduce in size.

Case 3

The 10-year-old sister of case 2 presented to the clinic for evaluation of a right submandibular mass. Family noticed the lump the day prior. She had several days of fever approximately a week before presentation. Her brother (case 2) was evaluated and treated for CSD a few weeks prior. On examination, she had a 1.5 cm mobile, minimally tender right submandibular lymph node. She was prescribed 5 days of azithromycin. At follow-up, lymphadenopathy improved without complication. At this time, the family noted that there were at least 20 cats at home, consisting of approximately 15 outdoor cats and 2 recent litters of kittens.

Discussion

Early recognition of CSD may prevent invasive diagnostic testing for other causes, such as malignancy and tuberculosis.^6-8 A known history of CSD in the family assisted in timely diagnosis and treatment of cases 2 and 3.^4,5 Since 1965, there have been a few intermittent case reports of familial CSD.^4,5,7,9-14 Cat scratch disease is typically characterized as a sporadic illness, occurring in isolated cases. ⁵ In the setting of common environmental exposure, it is unclear why familial outbreaks are not routine presentations of CSD. ¹⁵ In the literature, several factors for disease progression have been considered, including age of the host or human, age of the animal, or variation in bacterial virulence.^15,16 In addition, as CSD manifests in multiple presentations and often self-resolves, it is also possible that Bartonella causes may often go unrecognized.^15,17

In the United States, cats are present in more than 31 million households. ¹⁸ Seroprevalence of B henselae ranges from 30% to 40% in domestic and adopted shelter cats. ² Kittens and stray cats are more likely to be bacteremic. ² In some cases, kittens are given away after diagnosis of CSD in a human host. ⁵ There is currently no formal recommendation in place for removal of suspected bacteremic cats from the household.^2,15 In this case report, family kept the cats and kittens. Current guidelines for CSD prevention focus on patient education, flea eradication in pets, and avoidance of cat scratches or bites. Testing or treatment of suspected cats for Bartonella is not generally recommended. ²

In immunocompetent children with typical presentation of lymphadenopathy, antibiotic therapy is not recommended, ² although 5 days of azithromycin may be considered in mild to moderate cases. ⁶ Approximately 10% to 20% of lymph nodes affected in CSD become suppurative, and surgical intervention may be considered for relief of symptoms. ² It is notable that case 1’s presentation was more severe than other children in the household, requiring hospitalization and surgical intervention. Severity of symptoms varied between siblings in previous case reports.^4,11,14 Although CSD is generally a self-limiting disease, it is important to recognize that disease progression may still occur, despite multiple courses of antibiotics. ¹⁹

Conclusion

Consideration of CSD as a familial disease can assist clinicians in early diagnosis and treatment of CSD. This practice can prevent invasive testing and prolonged hospitalizations for other causes, such as malignancy.

Author Contributions

SL collected data, drafted the initial manuscript, and reviewed and revised the manuscript. MN collected data and reviewed and revised the manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.