Kikuchi-Fujimoto disease: a diagnostic dilemma

Distinguishing Kikuchi-Fujimoto disease from lymphoma in patients by clinical and PET/CT features

To develop a scheme for distinguishing Kikuchi-Fujimoto disease (KFD) from lymphoma in patients presenting enlarged lymph nodes (LNs) predominantly on the upper side of the diaphragm. From November 2015 to August 2023, 32 KFD patients and 38 lymphoma patients were pathologically confirmed and enrolled in this retrospectively study. Clinical and 18F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) features were collected. When comparing those PET/CT parameters, we set 5 models with different research objects: (1) all affected LNs; (2) the 5 largest affected LNs in terms of maximum diameter; (3) the 5 largest affected LNs in terms of maximum standard uptake values (SUVmax); (4) the largest affected LNs in terms of maximum diameter; (5) the largest affected LNs in terms of SUVmax. Compared to lymphoma patients, KFD patients were younger; and with higher incidence of fever, arthralgia, abnormal serum white blood cell, lactate dehydrogenase (LDH) and splenomegaly; lower incidence of affected LNs perinodal infiltration, necrosis and conglomeration; more affected LNs in Head and Neck nodes (particularly in level II) and Axillary in KFD (P ˂ .05). PET/CT parameters presented as various difference in each model. Finally, 11 clinical and PET/CT features (age ≤ 34, with fever, arthralgia, abnormal white blood cell, abnormal LDH, and without node necrosis and node conglomeration have a score of 2 each; splenomegaly, perinodal infiltration, median maximum diameter ≤ 20.5 and median SUVmax ≤ 7.1 of affected LNs in model 2 have score of 1 each) were selected as scheme items for distinguishing KFD from lymphoma. Individuals who have a total score > 8, meet the criteria for KFD. Sensitivity and specificity were high: 86.8% (95% CI: 71.9%, 95.5%) and 96.9% (95% CI: 83.7%, 99.5%), AUC = 0.975 (95% CI: 90.5%, 99.6%), respectively. It can effectively distinguish KFD from lymphoma by clinical and PET/CT parameters.

Kikuchi-Fujimoto disease, a rare benign disease with atypical histomorphology: more than meets the eye

Kikuchi-Fujimoto disease (KFD) is a benign self-limiting condition primarily affecting young females. It usually presents with fever and cervical lymphadenopathy of unknown aetiology with a preponderance of the Asian population. Histopathology is critical in making an accurate diagnosis. While the typical microscopic features include paracortical necrosis with debris, histiocytosis with immunoblasts, and absent neutrophils, rarely, KFD can show atypical features like marked immunoblastic proliferation mimicking lymphoma, demonstrate vasculitis mimicking lupus erythematosus, etc. The diagnosis is extremely challenging if such features occur in cases with generalised lymphadenopathy, which is infrequent in KFD. The study aims to describe the morphological, clinical, and immunohistochemical features of KFD and determine the frequency of the atypical features. We also analysed the subtle histological and immunohistochemical features that aid in the diagnosis of atypical cases. Cases reported as KFD over a period of 6 years were retrieved from the archives of histopathology. The morphological features were categorised as typical and atypical. In the atypical cases, the features that aided in the correct diagnosis of KFD were analysed. Out of the 42 cases evaluated, 23.9% (n=10) had generalised lymphadenopathy; 57.2% (n=24) were women with a median age of 25 years. Leukopenia was observed in 42% (n=13) of patients. Typical features were present in 76.2% (n=32) cases and 23.8% (n=10) presented with atypical features. Eight cases were antinuclear antibody-positive. Atypical features included five (50%) cases with vasculitis and panniculitis, and three (30%) cases with large, atypical cells for which immunohistochemistry (IHC) was performed. In two of these cases, the patent sinuses, absence of neutrophils, and IHC with CD68 aided the diagnosis. There is an overlap of clinical and histopathological features between KFD and malignant lymphomas and systemic lupus erythematosus. Given the fact that the atypical features (23.8%) are not rare occurrences in KFD, correlations with clinical findings and ancillary studies are essential to avoid misdiagnosis and inadvertent therapy.

Unlocking the Hidden Depths: Multi-Modal Integration of Imaging Mass Spectrometry-Based and Molecular Imaging Techniques

Multimodal imaging (MMI) has emerged as a powerful tool in clinical research, combining different imaging modes to acquire comprehensive information and enabling scientists and surgeons to study tissue identification, localization, metabolic activity, and molecular discovery, thus aiding in disease progression analysis. While multimodal instruments are gaining popularity, challenges such as non-standardized characteristics, custom software, inadequate commercial support, and integration issues with other instruments need to be addressed. The field of multimodal imaging or multiplexed imaging allows for simultaneous signal reproduction from multiple imaging strategies. Intraoperatively, MMI can be integrated into frameless stereotactic surgery. Recent developments in medical imaging modalities such as magnetic resonance imaging (MRI), and Positron Emission Topography (PET) have brought new perspectives to multimodal imaging, enabling early cancer detection, molecular tracking, and real-time progression monitoring. Despite the evidence supporting the role of MMI in surgical decision-making, there is a need for comprehensive studies to validate and perform integration at the intersection of multiple imaging technologies. They were integrating mass spectrometry-based technologies (e.g., imaging mass spectrometry (IMS), imaging mass cytometry (IMC), and Ion mobility mass spectrometry ((IM-IM) with medical imaging modalities, offering promising avenues for molecular discovery and clinical applications. This review emphasizes the potential of multi-omics approaches in tissue mapping using MMI integrated into desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI), allowing for sequential analyses of the same section. By addressing existing knowledge gaps, this review encourages future research endeavors toward multi-omics approaches, providing a roadmap for future research and enhancing the value of MMI in molecular pathology for diagnosis.

Elevated serum IFN-γand IFN-γ/IL-6 ratio in Kikuchi-Fujimoto disease

BACKGROUND

Kikuchi-Fujimoto disease (KFD) is typically a benign, self-limiting inflammatory disease. The diagnosis of KFD can be challenging for nonspecific symptoms, laboratory or imaging findings. In this study, we aimed to describe the clinical manifestations of patients with KFD and to access the potential role of serum cytokines in the diagnosis of this disease.

METHODS

Patients with KFD were retrospectively enrolled from January 2015 to November 2021 at Shenzhen Children's Hospital. Clinical data were collected from inpatient or outpatient medical records. Serum cytokines were detected by the Flowcytomix technique. Serum levels of cytokines were compared between patients with KFD and SJIA, or patients with KFD and KD. The data of patients without MAS were further analyzed. A receiver operating characteristic (ROC) curve analysis was further performed to access the potential role of serum cytokines in the diagnosis of KFD.

RESULTS

Serum cytokines were detected in 25 (43.8%, 25/57) patients with a histological diagnosis of KFD. Compared to SJIA or KD patients, the KFD group had a significantly higher IFN-γ/IL-6 ratio and much lower levels of serum IL-6. The median level of serum IFN-γ in KFD was 41.65 pg/ml (range, 21.04-70.74 pg/ml), which was much higher than that in SJIA (median: 3.33 pg/ml, p = 0.16) or KD (median: 2.6 pg/ml, p = 0.01). After excluding patients with MAS, there was statistical significance in all comparisons of serum IFN-γ, IFN-γ/IL-6 ratio, and serum IL-6. The cutoff values of serum IFN-γ, IL-6, and IFN-γ/IL-6 ratio for differentiating KFD from SJIA were > 8.48 pg/ml, < 47.42 pg/ml, and > 0.45, respectively. The cutoff values of serum IFN-γ, IL-6, and IFN-γ/IL-6 ratio for differentiating KFD from KD were > 8.56 pg/ml, < 50.45 pg/ml, and > 0.45, respectively. The specificity of all those cutoff values for differentiating KFD from SJIA or KD was ≥ 94.7%.

CONCLUSIONS

For patients with fever of unknown etiology and lymphadenopathy, after excluding HLH or MAS, serum IFN-γ > 8.56 pg/mL and IFN-γ/IL-6 ratio > 0.45 may highly suggest the diagnosis of KFD; serum IL-6 > 50.45 pg/mL indicates that the probability of KFD may be small, and sJIA, KD, and acute infection should be excluded first.

Structured diagnostic scheme clinical experience sharing: a prospective study of 320 cases of fever of unknown origin in a tertiary hospital in North China

BACKGROUND

There has been little research on the long-term clinical outcomes of patients discharged due to undiagnosed fevers of unknown origin (FUO). The purpose of this study was to determine how fever of unknown origin (FUO) evolves over time and to determine the prognosis of patients in order to guide clinical diagnosis and treatment decisions.

METHODS

Based on FUO structured diagnosis scheme, prospectively included 320 patients who hospitalized at the Department of Infectious Diseases of the Second Hospital of Hebei Medical University from March 15, 2016 to December 31,2019 with FUO, to analysis the cause of FUO, pathogenetic distribution and prognosis, and to compare the etiological distribution of FUO between different years, genders, ages, and duration of fever.

RESULTS

Among the 320 patients, 279 were finally diagnosed through various types of examination or diagnostic methods, and the diagnosis rate was 87.2%. Among all the causes of FUO, 69.3% were infectious diseases, of which Urinary tract infection 12.8% and lung infection 9.7% were the most common. The majority of pathogens are bacteria. Among contagious diseases, brucellosis is the most common. Non-infectious inflammatory diseases were responsible for 6.3% of cases, of which systemic lupus erythematosus(SLE) 1.9% was the most common; 5% were neoplastic diseases; 5.3% were other diseases; and in 12.8% of cases, the cause was unclear. In 2018-2019, the proportion of infectious diseases in FUO was higher than 2016-2017 (P < 0.05). The proportion of infectious diseases was higher in men and older FUO than in women and young and middle-aged (P < 0.05). According to follow-up, the mortality rate of FUO patients during hospitalization was low at 1.9%.

CONCLUSIONS

Infectious diseases are the principal cause of FUO. There are temporal differences in the etiological distribution of FUO, and the etiology of FUO is closely related to the prognosis. It is important to identify the etiology of patients with worsening or unrelieved disease.

Pathological Features and Clinical Characteristics of Kikuchi-Fujimoto Disease: A Tertiary Hospital Experience in Riyadh, Saudi Arabia

Background Kikuchi-Fujimoto disease (KFD) - also known as necrotizing histiocytic lymphadenitis - is a benign histiocytic lymphadenitis known for its low incidence and misdiagnosis that occurs mostly in young Asian females more than males. This disease resolves spontaneously in a few months with a low risk of relapse (one in 30 patients) after resolution. Objectives The aim of this study is to share King Abdulaziz Medical City's (KAMC's) experience with KFD by determining its clinicopathological characteristics. Materials and methods In this study, we reviewed histopathological slides and pathological reports of all lymphadenopathy cases (683 cases) in the period between January 2008 and December 2018. Results Forty-four cases of KFD were found and their clinicopathological characteristics were recorded. There is a slight female predominance (59% females versus 41% males) with a wide age range from 10 months to 97 years (mean = 28.8). The majority of the cases (63.6%) are seen in young adults (between 21 and 40 years). Association with autoimmune diseases was shown by 20.5% of cases while viral infection association was shown by few cases. Most cases showed remission (59%) and no deaths were reported upon follow-up. Histopathologically, the majority of cases have proliferative type followed by the necrotic type and few cases showed xanthomatous type. Conclusions Our study has the largest number of KFD cases in this region. It is obvious that KFD has clinical, radiological, and pathological features that overlap with malignancy, especially lymphoma. Knowing this disease and careful diagnostic approach can help avoid misdiagnosis.

Aseptic meningitis in Kikuchi-Fujimoto Disease - Rare manifestation of a rare disease

Kikuchi-Fujimoto Disease (KFD) is a rare disease marked by necrotizing lymphadenitis, often presenting as unilateral cervical lymphadenopathy, along with various extranodal manifestations such as fever, skin rash, hepatosplenomegaly, and arthritis, etc. KFD is thought to be secondary to either a viral infection or an autoimmune process, however, evidence in favor of both models is scarce and non-definitive. We report a case of a young female who presented with persistent high-grade fever, bilateral cervical and axillary lymphadenopathy, and leukopenia. Excisional biopsy of affected lymph nodes revealed well-circumscribed foci of necrosis with karyorrhectic debris and scattered fibrin deposits characteristic of KFD. The patient was promptly initiated on non-steroidal anti-inflammatory drugs (NSAIDs), however, despite an early improvement in symptoms, the patient soon developed aseptic meningitis, a rare neurological complication of KFD. Intravenous followed by oral corticosteroid therapy reported a good prognosis, with no observable residual neurological deficits. Knowledge of the disease and its complications significantly helped in the avoidance of unnecessary investigations and a delay in treatment.

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Central nervous system involvement may be seen in Kikuchi Fujimoto Disease (KFD).

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Aseptic meningitis is a rare neurological complication of KFD.

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It may present after the resolution of KFD symptoms.

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Prompt treatment and recognition holds favorable prognosis.

Self-limiting COVID-19-associated Kikuchi-Fujimoto disease with heart involvement: case-based review

Background

The association between COVID-19 infection and the development of autoimmune diseases is currently unknown, but there are already reports presenting induction of different autoantibodies by SARS-CoV-2 infection. Kikuchi-Fuimoto disease (KFD) as a form of histiocytic necrotizing lymphadenitis of unknown origin.

Objective

Here we present a rare case of KFD with heart involvement after COVID-19 infection. To our best knowledge only a few cases of COVID-19-associated KFD were published so far. Based on presented case, we summarize the clinical course of KFD and its association with autoimmune diseases, as well we discuss the potential causes of perimyocarditis in this case.

Methods

We reviewed the literature regarding cases of “Kikuchi-Fujimoto disease (KFD)” and “COVID-19” and then “KFD” and “heart” or “myocarditis” by searching medical journal databases written in English in PubMed and Google Scholar.

Results

Only two cases of KFD after COVID infection have been described so far.

Conclusion

SARS-CoV-2 infection can also be a new, potential causative agent of developing KFD.

Kikuchi-Fujimoto Disease Following COVID-19

Kikuchi-Fujimoto Disease (KFD) is a rare self-limiting condition of unknown etiology. It is characterized by fever, and lymphadenopathy most commonly involving posterior cervical lymph nodes. Although it is of uncertain etiology, it is associated with viral infections and autoimmune diseases. Distinction from lymphadenopathy-associated alternate disorders is crucial to avoid unneeded diagnostic procedures and treatment. KFD is diagnosed based on histopathologic examination of the excised lymph node. The management is supportive with favorable outcomes within a few weeks or months. In this case, we describe a 13-year-old boy who complained of painful cervical lymphadenopathy and fever for more than three weeks following COVID-19. Diagnostic workup has been established and KFD diagnosis made based on the histopathologic features of the involved lymph node. The patient showed complete recovery with no recurrence during follow-up. So, this case highlights the possible association between COVID-19 and KFD during this pandemic and keeping it in the differential diagnosis.

Kikuchi-Fujimoto Disease With Unusual Cutaneous Findings

ABSTRACT

We present a case of the rare Kikuchi-Fujimoto disease (KFD) in a 14-year-old patient admitted to UCLA Medical Center with fever, weight loss, and pancytopenia. Physical examination revealed tender subcutaneous nodules and cervical lymphadenopathy. A lymph node biopsy showed findings consistent with KFD. The skin biopsy showed mild superficial dermal edema with neutrophil-predominant inflammation. In addition, rare atypical monocytoid cells were seen. This histologic finding of a Sweet-like morphology has not been reported previously in the literature in association with KFD. The differential diagnosis included Sweet syndrome arising in association with KFD, underlying connective tissue, and an infectious etiology.

The great masquerader: Kikuchi-Fujimoto disease presenting as fever of unknown origin

INTRODUCTION

Kikuchi-Fujimoto (KF) disease, also known as necrotizing histiocytic lymphadenitis, is a rare cause of fever of unknown origin. Most commonly seen in Japanese populations, it presents with fever and diffuse lymphadenopathy. KF can present a diagnostic challenge as its presentation can mimic sepsis, autoimmune disease, and/or malignancy. We present a case of KF disease presenting with innumerable pulmonary nodules and suspected sepsis.

CASE REPORT

A 24-year old African-American male inmate with no past medical history presented to the Emergency Department with two witnessed generalized tonic-clonic seizures. Initial vitals were notable for a fever of 101.5 F, tachycardia, and tachypnea. He was lethargic with a diffuse, erythematous, scaly, necrotic rash. Additionally, cervical, axillary, and inguinal mobile, non-tender lymph nodes were noted. Laboratory studies revealed white blood cells 1.9 × 10 3 cells/μL with 25% bands, hemoglobin 9.4 G/dL, and platelet count of 110 × 10 3 cells/μL. He was subsequently admitted for sepsis due to presumed meningitis and started on broad-spectrum antibiotics. Lumbar puncture revealed no pleocytosis. Peripheral blood smear showed bandemia with Pelger Huet cells. Computed Tomography of chest, abdomen, and pelvis with contrast revealed diffuse pulmonary nodules involving all lobes of the lungs in addition to bulky hilar and retroperitoneal lymphadenopathy. Interventional Radiology performed a retroperitoneal lymph nodes biopsy that revealed lymphoplasmacytic cell infiltrate with extensive necrosis. Otolaryngology performed an excisional biopsy of a lymph node, which showed histiocytic necrotizing lymphadenitis. The final diagnosis was Kikuchi-Fujimoto disease, also known as histiocytic necrotizing lymphadenitis.

OUTCOME

The patient completed a 7-day course of empiric antibiotics. Workup for infectious etiologies was negative. The patient had a repeat CT of the chest with interval resolution of his pulmonary nodules on outpatient follow-up.

CONCLUSION

Patients with innumerable pulmonary nodules and fever of unknown origin should be evaluated early in their hospital course for KF as early diagnosis can reduce excessive testing and shorten hospital stay.

Kikuchi-Fujimoto Disease Triggered by Systemic Lupus Erythematosus and Mycoplasma pneumoniae Infection-A Report of a Case and a Review of the Literature

ABSTRACT

Kikuchi-Fujimoto disease (KFD) is a necrotizing histiocytic lymphadenitis that was described for the first time in 1972 in Japan. Its etiology is still not fully understood. It has been reported in association with many different agents, diseases, and triggering factors without any conclusive result. To the best of our knowledge, we report for the first time a case of KFD with systemic lupus erythematosus in a child in association with a polymerase chain reaction (PCR)-positive throat swab for Mycoplasma pneumoniae. Although difficult to prove, the acute M. pneumoniae infection might have served as a triggering event for the development of KFD in our case. We encourage further studies to investigate a potential relationship between KFD and M. pneumoniae, which should also use PCR-based testing for this pathogen in patients with KFD.

Development of Kikuchi-Fujimoto disease after a cervical lymph node metastasis of mucoepidermoid carcinoma: a case report

Kikuchi-Fujimoto disease (KFD) was first reported by Kikuchi and Fujimoto in 1972 as a rare disease with lymphadenitis of unknown etiology. KFD is characterized by the main symptoms of fever and enlarged cervical lymph nodes (LNs), which are similar to the features of other LN-associated diseases. Therefore, it is difficult to diagnose this condition. We report the case of a 24-year-old woman who presented with KFD after surgery to treat a mucoepidermoid carcinoma of the palate and dissection of the left neck. The patient presented with a fever and right cervical lymphadenopathy when she visited our department for a regular follow-up related to the mucoepidermoid carcinoma. The results of computed tomography and ultrasonography evaluations led to a clinical diagnosis of lymph node metastasis, and a right neck dissection was performed. However, the pathological tissue analysis did not suggest malignancy but showed necrosis and various cellular infiltrates. We made a diagnosis of KFD from these clinical and pathological features. KFD may be misdiagnosed as a LN-associated disease such as metastasis. Clinically, KFD should be considered in patients with head and neck cancer who present with cervical lymphadenopathy.

A Case of Kikuchi-Fujimoto Disease Associated with Erosive Lichen Planus

Kikuchi-Fujimoto disease (KFD), also known as histiocytic necrotizing lymphadenitis, is a benign, self-limiting disorder with unknown etiology. The most frequent clinical manifestations include lymphadenopathy, fever, cutaneous lesions, arthritis, fatigue, and hepatosplenomegaly. Cutaneous manifestations of KFD, occurring in about one-third of patients, are typically non-specific, rarely presenting as symmetrically distributed lesions. The prevalence of erosive lichen planus in patients with KFD, as of this date, is unknown with no previously reported cases describing an association between the two conditions. In the following case report, we report a case presenting with bilateral symmetrical erosive lichen planus of the heel associated with KFD as being a possible, rather novel, cutaneous manifestation.

Necrotizing lymphadenitis: Not always tuberculosis, its Kikuchi-Fujimoto's disease

Kikuchi-Fujimoto's disease is an uncommon self limiting, benign cause of generalised lymphadenopathy with fever. It can present as a triad of fever, night sweats and lymphadenopathy which resembles more common causes like tuberculosis and lymphoma. Being an endemic country a patient may be treated on the lines of tuberculosis often. We present case of a young female who was diagnosed as Kikuchi-Fujimoto's disease after not responding to antitubercular treatment. Pathologists and Clinicians must be aware of this condition to prevent unnecessary treatment.

Evaluation of macrophage activation syndrome in hospitalised patients with Kikuchi-Fujimoto disease based on the 2016 EULAR/ACR/PRINTO classification criteria

BACKGROUND

To evaluate the impact of macrophage activation syndrome (MAS) on clinical features in patients with Kikuchi-Fujimoto disease (KFD) and to compare the features of MAS in KFD with those of adult-onset Still's disease (AOSD) and systemic lupus erythematosus (SLE).

METHODS

The medical records of febrile patients hospitalised with KFD between November 2005 and April 2017 were reviewed. Patients fulfilling the 2016 classification criteria for MAS were classified as having MAS. Clinical and laboratory features of patients with KFD with and without MAS were evaluated. Poor hospitalisation outcomes were defined as intensive care unit admission or in-hospital mortality. The treatment outcomes of MAS in KFD, AOSD, and SLE were also compared.

RESULTS

Among 78 patients hospitalised with KFD, 24 (30.8%) patients had MAS during admission. Patients with KFD and MAS more frequently required glucocorticoid treatment (66.7% vs 40.7%, p = 0.036) and had longer hospital stays than patients with KFD without MAS (12.5 vs 8.5 days, p<0.001). In addition, patients with MAS had worse hospitalisation outcomes than patients without MAS (29.2% vs. 0.0%, p<0.001). Among patients with MAS in KFD, AOSD, and SLE, the number of patients requiring glucocorticoid treatment after 3 months was significantly lower among patients with MAS and KFD (KFD 33.3%, AOSD 88.9%, SLE 100%, p<0.001).

CONCLUSIONS

The presence of MAS in KFD was associated with adverse clinical outcomes including higher steroid usage and worse hospitalisation outcomes. However, compared to those with AOSD and SLE, patients with MAS and KFD were less likely to require long-term glucocorticoid treatment.

Is recurrent Kikuchi-Fujimoto disease a precursor to systemic lupus erythematosus?

Kikuchi-Fujimoto disease (KFD), also known as histiocytic necrotizing lymphadenitis, is a rare, benign, self-limiting disease characterized by cervical lymphadenopathy and fever. Since KFD was first reported in 1972, the validity of this clinical entity has been controversial and its aetiology remains unknown. Herein, we report a case of a patient with KFD, which was believed to be associated with systemic lupus erythematosus.

Take a second look: it's Kikuchi's disease! A case report and review of literature

Generalized lymphadenopathy is a common cause of concern for both patients and clinicians. Possible etiologies include infections, malignancies and autoimmune diseases. Kikuchi Fujimoto disease (KFD) is a hyperergic condition that presents with fever, lymphadenopathy and can include systemic involvement, thus being easily mistaken for the above-mentioned entities. We report the case of a previously healthy 18- year old male who presented with a selflimiting generalized lymphadenopathy, high fevers, skin vasculitis and polyserositis. The lymph-node biopsy revealed a histiocytotic necrotizing lymphadenitis, suggestive of Kikuchi’s disease. This case emphasizes the importance of KFD in the differential diagnosis of lymphadenopathy, especially in young adults.

A Mimic of Posttransplant Lymphoproliferative Disease Following Liver Transplant

Generalized lymphadenopathy after organ transplant is a concerning finding, often indicating the devel-opment of lymphoma. We describe a 52-year-old liver transplant recipient who had clinical symptoms and imaging concerning for posttransplant lymphoproliferative disease. However, histologic evaluation of a lymph node biopsy revealed that the patient actually had a much rarer but relatively benign condition, Kikuchi-Fujimoto disease (histiocytic necrotizing lymphadenitis). We discuss the epidemiology, clinical symptoms, diagnosis, histologic features, and treatment of this uncommon mimic of posttransplant lymphoproliferative disease.