Characteristic Distribution Pattern of CD30-positive Cytotoxic T Cells Aids Diagnosis of Kikuchi-Fujimoto Disease

Kikuchi-Fujimoto disease: A comprehensive review

Kikuchi-Fujimoto disease, a rare form of necrotizing lymphadenitis, is an uncommon, benign, self-limiting disorder of obscure etiology. It affects mostly young adults of both genders. Clinically, it presents with fever and lymphadenopathy of a firm to rubbery consistency frequently involving cervical lymph nodes while weight loss, splenomegaly, leucopenia, and elevated erythrocyte sedimentation rate feature in severely affected patients. Cutaneous involvement occurs in about 30%-40% of cases as facial erythema and nonspecific erythematous papules, plaques, acneiform or morbilliform lesions of great histologic heterogeneity. Both Kikuchi-Fujimoto disease and systemic lupus erythematosus share an obscure and complex relationship as systemic lupus erythematosus may occasionally precede, develop subsequently, or sometimes be associated concurrently with Kikuchi-Fujimoto disease. It is often mistaken for non-Hodgkin lymphoma while lupus lymphadenitis, cat-scratch disease, Sweet’s syndrome, Still’s disease, drug eruptions, infectious mononucleosis, and viral or tubercular lymphadenitis are other common differentials. Fine needle aspiration cytology mostly has features of nonspecific reactive lymphadenitis and immunohistochemistry studies usually show variable features of uncertain diagnostic value. Since its diagnosis is exclusively from histopathology, it needs to be evaluated more carefully; an early lymph node biopsy will obviate the need for unnecessary investigations and therapeutic trials. Its treatment with systemic corticosteroids, hydroxychloroquine, or antimicrobial agents mostly remains empirical. The article reviews clinicoepidemiological, diagnostic, and management aspects of KFD from the perspective of practicing clinicians.

A Malignant Mimicker: Features of Kikuchi-Fujimoto Disease in the Pediatric Population

BACKGROUND

Kikuchi-Fujimoto disease (KFD) is a rare, benign, and self-limited disease that presents with cervical lymphadenopathy and systemic symptoms. Histologic evaluation is often necessary to differentiate KFD from other entities.

METHODS

Electronic medical records and diagnostic material were reviewed for 14 children diagnosed with KFD and 6 children diagnosed with infectious mononucleosis (IM) from 2013-2021. Four cases of KFD were further characterized using targeted DNA-based next-generation sequencing.

RESULTS

Systemic symptoms were present in 86% (n = 12/14) of KFD patients, the most common being fever. Laboratory values worrisome for malignancy included cytopenia(s) (n = 9/12), elevated ESR and/or CRP (n = 9/12), elevated ferritin (n = 7/7), and elevated LDH (n = 7/10). Histologically, lymph nodes showed characteristic necrotic foci without neutrophils surrounded by MPO+ "crescentic" histiocytes. Immunoblasts and CD123+ plasmacytoid dendritic cells (pDCs) were also increased surrounding the necrosis. IM lymph nodes showed similar features when necrosis was present but increases in pDCs were patchy and rare neutrophils were seen in the necrotic foci. Molecular analysis of 4 KFD cases did not identify pathogenic variants.

CONCLUSION

While the signs/symptoms of KFD are worrisome, there are pathologic features that help differentiate it from potential mimics. We did not identify characteristic molecular features to aid in the work-up of these cases.

Kikuchi-Fujimoto disease is mediated by an aberrant type I interferon response

Kikuchi-Fujimoto disease (KFD) is a reactive lymphadenitis of unclear etiology. To understand the pathogenesis of KFD, we performed targeted RNA sequencing of a well-characterized cohort of 15 KFD specimens with 9 non-KFD lymphadenitis controls. Two thousand and three autoimmunity-related genes were evaluated from archived formalin-fixed paraffin-embedded lymph node tissue and analyzed by a bioinformatics approach. Differential expression analysis of KFD cases compared to controls revealed 44 significantly upregulated genes in KFD. Sixty-eight percent of these genes were associated with the type I interferon (IFN) response pathway. Key component of the pathway including nucleic acid sensors, IFN regulatory factors, IFN-induced antiviral proteins, IFN transcription factors, IFN-stimulated genes, and IFN-induced cytokines were significantly upregulated. Unbiased gene expression pathway analysis revealed enrichment of IFN signaling and antiviral pathways in KFD. Protein-protein interaction analysis and a molecular complex detection algorithm identified a densely interacting 15-gene module of type I IFN pathway genes. Apoptosis regulator IFI6 was identified as a key seed gene. Transcription factor target analysis identified enrichment of IFN-response elements and IFN-response factors. T-cell-associated genes were upregulated while myeloid and B-cell-associated genes were downregulated in KFD. CD123+ plasmacytoid dendritic cells (PDCs) and activated T cells were noted in KFD. In conclusion, KFD is mediated by an aberrant type I interferon response that is likely driven by PDCs and T cells.

Distinguishing lupus lymphadenitis from Kikuchi disease based on clinicopathological features and C4d immunohistochemistry

OBJECTIVES

Distinguishing Kikuchi disease (KD) from lupus lymphadenitis (LL) histologically is nearly impossible. We applied C4d immunohistochemical (IHC) stain to develop diagnostic tools.

METHODS

We retrospectively investigated clinicopathological features and C4d IHC staining in an LL-enriched development cohort (19 LL and 81 KD specimens), proposed risk stratification criteria and trained machine learning models, and validated them in an external cohort (2 LL and 55 KD specimens).

RESULTS

Clinically, we observed that LL was associated with an older average age (33 vs 25 years; P=0.005), higher proportion of biopsy sites other than the neck [4/19 (21%) vs 1/81 (1%); P=0.004], and higher proportion of generalized lymphadenopathy compared with KD [9/16 (56%) vs 7/31 (23%); P=0.028]. Histologically, LL involved a larger tissue area than KD did (P=0.006). LL specimens exhibited more frequent interfollicular pattern [5/19 (26%) vs 3/81 (4%); P=0.001] and plasma cell infiltrates (P=0.002), and less frequent histiocytic infiltrates in the necrotic area (P=0.030). Xanthomatous infiltrates were noted in 6/19 (32%) LL specimens. Immunohistochemically, C4d endothelial staining in the necrotic area [11/17 (65%) vs 2/62 (3%); P<10-7], and capillaries/venules [5/19 (26%) vs 7/81 (9%); P=0.048] and trabecular/hilar vessels [11/18 (61%) vs 8/81 (10%); P<10-4] in the viable area was more common in LL. During validation, both the risk stratification criteria and machine learning models were superior to conventional histological criteria.

CONCLUSIONS

Integrating clinicopathological and C4d findings could distinguish LL from KD.

An atypical presentation of Kikuchi-Fujimoto disease: A case report & literature review

The authors urge clinicians to consider the possibility of Kikuchi-Fujimoto Disease associated with autoimmune hemolytic anemia with possible correlation with systemic lupus erythematosus in patients presented with lymphadenopathy and fever.