Kikuchi–Fujimoto Disease Secondary to Disseminated Brucellosis in an Adolescent Boy

To the Editors:

Brucellosis is the most common zoonotic disease worldwide, mainly caused by Brucella melitensis, followed by B. suis.¹ The typical presentations in children are insidious onset fever, night sweats, malaise, weight loss, and joint pain. Occasionally, a child may present with one or more complications that pose a diagnostic challenge to the clinician.^2,3 We report a rare complication of disseminated brucellosis in an adolescent boy.

A 15-year-old previously healthy boy presented with fever and headache for one month and neck swelling for 15 days. The fever was intermittent, low grade, and relieved with medication. Headache was moderate in intensity, generalized, and throbbing in nature. It was not associated with nausea, projectile vomiting, or abnormal body movement. The neck swelling was not associated with pain, discharge, or redness. The child had no history of tuberculosis (TB) contact, weight loss, intake of unpasteurized milk, joint involvement, or oral ulcers. He received antibiotics for the same without any improvement.

The child was hemodynamically stable, with normal anthropometry for age, and no pallor, icterus, or pedal edema. The child had generalized lymphadenopathy (LN), was matted, nontender, mobile, and had firm consistency, largest measured 3 cm × 2 cm in the cervical region. The systemic examinations were normal.

The initial possibilities of infection (bacterial, viral, mycobacterial) and malignancy (lymphoma or leukemia) were kept and investigated. His hemogram was normal. The peripheral smear did not show any atypical cells. However, he had raised inflammatory markers (ESR: 47 mm/1 hour; C-reactive protein: 3 mg/L; and IL-6: 405.4 pg/mL). Liver function tests showed only increased transaminases (alanine transaminase: 268 IU/L; aspartate transaminase: 238 IU/L). Renal function test was normal. In the TB workup, Mantoux was negative. There was an enlarged right paratracheal LN in the chest x-ray. Gastric aspirate (GA) was negative for acid-fast bacilli (AFB) and cartridge-based nucleic acid amplification test (CBNAAT). Contrast-enhanced computed tomography (CECT) thorax revealed necrotizing mediastinal LN.

HIV, scrub typhus serology, and testing for malarial antigens were negative. The blood culture was sterile. A fine needle aspiration cytology (FNAC) was done from cervical LN, demonstrating necrotizing granulomatous lymphadenitis. The AFB and CBNAAT were negative, and the culture was sterile in FNAC. Brucella serology {Enzyme-linked Immunosorbent assay (ELISA)} showed IgM positive. A working diagnosis of brucellosis was made, and he was started on triple-drug therapy (Doxycycline, Streptomycin, and Rifampicin). The Brucella IgG became positive after 2-weeks, which further confirmed the diagnosis.

Because of persistent headaches, a CSF examination was done, which was normal. A contrast-enhanced MRI brain was done, which revealed features of pachymeningitis (Figure 1). Since the child had a persistent fever, an excisional LN biopsy was done. It showed the characteristics of Kikuchi-Fujimoto disease (KFD) (e_figure-1, Supplementary Digital Content, https://links.lww.com/INF/E870). A final diagnosis of KFD secondary to disseminated brucellosis was made. He was continued on triple-drug therapy, and oral steroid was added. Following that, the child showed significant clinical improvement.

FIGURE 1.: MRI and CT imaging. (A) Axial T2-FLAIR image shows hyperintensity and enlargement of the left lacrimal gland (white arrow) with associated edematous changes in overlying soft tissues. (B) Coronal post-contrast T1WI shows predominantly pachymeningeal enhancement (black arrows) with mild leptomeningeal enhancement. (C) Axial post-contrast T1WI depicts abnormal enlargement and enhancement of the left parotid gland (star). (D) Contrast-enhanced CT axial image shows multiple enlarged deep cervical lymph nodes with small areas of central necrosis and periadenitis (arrowheads). Mediastinal lymph nodes were also present in this case (not shown).

This case highlights that brucellosis may present with one or more complications. The index case was diagnosed with disseminated brucellosis and subsequently found to have pachymeningitis and KFD. Both are very rare complications of brucellosis that occur due to altered immune responses to brucellosis.^4,5 In conclusion, the possibility of complications should be kept when a child does not respond to adequate therapy.