O2219: Renal abscess masquerading as tumor in a child with undiagnosed chronic granulomatous disease

Introduction: Chronic Granulomatous Disease (CGD) is a rare genetic immunodeficiency disorder that predisposes individuals to recurrent bacterial and fungal infections, particularly in the skin, lungs, lymph nodes, liver, and bones. We present a case of a pediatric patient with a renal mass, initially suspected to be malignant. However, 16S PCR on tissue obtained from a kidney biopsy confirmed the presence of Staphylococcus aureus in the specimen, suggestive of an abscess. The diagnosis of CGD was ultimately confirmed with an abnormally low Neutrophil Oxidative Burst Index (NOBI).

Case Description: An 11-year-old female presented to the Emergency Department of a community hospital with a 5-day history of fever and intermittent right lower quadrant pain. She was transferred to a quaternary pediatric hospital due to concerns for a right renal neoplasm. On admission, her white blood cell count (WBC) was 13,000/μL, and C-reactive protein (CRP) was 293 mg/L. Urinalysis was negative for nitrites and leukocytes, and blood and urine cultures were negative. She was initially treated with IV ceftriaxone, which was later switched to IV piperacillin-tazobactam. The patient had been previously healthy but had one prior episode of Staphylococcus cervical lymphadenitis/abscess at the age of 5, requiring surgical drainage.

Discussion: CT imaging revealed a multiloculated right renal mass measuring 3.3 x 4.5 x 4.3 cm, suggestive of a neoplastic process vs. an abscess. The patient underwent an image-guided biopsy and aspiration on day 7 of admission, obtaining 15 mL of purulent fluid for culture. Gram stain revealed Gram-positive cocci, but the culture was negative. However, 16S rRNA PCR testing was positive for Staphylococcus aureus. Pathology confirmed no malignancy. By day 11, the patient's fever pattern and inflammatory markers began to improve. Her pain was managed by the acute pain service, and she was switched to oral amoxicillin-clavulanate before discharge on day 18. She was kept on oral cephalexin until the abscess fully resolved on serial imaging studies. Given her history of recurrent deep infections caused by Staphylococcus aureus, a low NOBI (15; normal ≥32) was noted, with a repeat NOBI of 5, consistent with CGD. Further genetic testing is pending. Immunology was consulted and started prophylactic itraconazole and sulfamethoxazole-trimethoprim, following completion of cephalexin treatment.

Conclusion: CGD should be considered in the differential diagnosis of atypical renal masses and recurrent deep-seated infections. In this case, kidney biopsy was essential for confirming the diagnosis and guiding treatment, preventing an upfront nephrectomy due to concerns of malignancy.