Rare, but How Rare? A Case of Pediatric Kikuchi-fujimoto Disease and an Estimated US Prevalence

Introduction: When a cause can be identified, fever of unknown (FUO) origin is usually due to an infectious, oncologic, or autoimmune etiology. Rarely, Kikuchi-Fujimoto Disease (KFD) is the cause. We present a case of Pediatric KFD in the USA along with a review of the literature to determine just how rare it is.

Case Description: A previously healthy 11-year-old Hispanic male presented with right lower extremity pain in the setting of three weeks of cervical adenopathy and daily fevers of 39-40°C. Previous outpatient workup was notable for neutropenia and elevated lactate dehydrogenase. Initial physical exam showed non-tender cervical lymphadenopathy, mild splenomegaly, and papules on his right shoulder, arm, nose, and bilateral thighs. Right midcalf muscular pain was present on palpation without edema or erythema, and gait was notable for a mild limp. He was admitted to the ward and an FUO workup was initiated. While the calf pain resolved, the skin lesions enlarged before the pustules ruptured and crusted over (Figure 1). ID workup was notable for EBV IgG antibodies. During work-up for malignancy, he underwent a cervical lymph node excisional biopsy. Examination showed an appearance characteristic of KFD and lupus lymphadenitis (Figure 2). The patient’s ANA panel was negative, making KFD the favored diagnosis.

Discussion: Kikuchi-Fujimoto Disease (KFD) was first described in Japan in 1972 by Kikuchi and Fujimoto. The etiology of KFD is currently unknown, with theories favoring a post-viral syndrome. Previous studies show an association with EBV (as seen in our patient), HHV-6,7,8, HSV, Human T lymphotropic virus, and Parvovirus B19. KFD can present acutely or sub-acutely, with the most common features being low-grade fever, headache, weight loss, nonspecific cutaneous lesions, and painful cervical lymphadenopathy. Laboratory workup can show leukopenia, increased inflammatory markers, anemia, thrombocytopenia, elevated ALT, and increased LDH. Diagnosis is made through lymph node biopsy and histologic examination. Prognosis is mostly favorable with most cases self-resolving, but a few cases demonstrate reoccurrence or later development of SLE. KFD most commonly occurs in women of Asian descent between 20-30 years old, with rare occurrences in non-Asian ethnic groups. Inversely, pediatric populations have a slightly greater occurrence in males. Review of the literature shows no consensus of the current prevalence of KFD in the world. A thorough review of pediatric KFD cases published in the United States from 1972-2020 revealed 23 confirmed cases of KFD. Ours appears to be the first of such reviews to determine an estimated prevalence of pediatric KFD in the United States.

Conclusion: KFD is a rare condition that is even more uncommon in U.S. Pediatric populations, with only 24 known cases including this patient. Though the presentation is varied, and definitive diagnosis requires lymph node biopsy, the prognosis is good as it commonly self resolves.