Unusual gingival actinomycosis post allogeneic hematopoietic stem-cell transplant: case report

Abstract

Background: Allogeneic hematopoietic stem cell transplant (allo-HSCT) is used to treat several hematological diseases, but immunosuppression during allo-HSCT facilitates opportunistic microbial growth in tissues, such as actinomycosis. An effective diagnosis of opportunistic diseases is essential for correct management of the disease and preservation of the immunosuppressed patient's life.

Case description: A 57-year-old female patient was diagnosed with extranodal nasal type NK/T cell lymphoma and underwent curative treatment with allo-HSCT. Twenty-one days after the last clinical follow-up, the patient presented a necrotizing lesion in the papilla region between the first and second molars of the second quadrant. Histopathological analysis showed the presence of a bacterial cluster consistent with Actinomyces infection, and a dense lymphoid infiltrate was also observed. Immunohistochemistry for CD20, CD3, and CD56 was performed to exclude the possibility of the recurrence of extranodal NK/T cell lymphoma. Oral microbiota profiling showed a huge increase in the abundance of Actinomyces bacteria in the subgingival region three weeks prior to appearance of the lesion.

Conclusions: Opportunistic infections with an unusual clinical appearance are confounding factors in therapeutic decision-making. We present for the first time a case of actinomycosis in the gingival papilla region following allo-HSCT. We also highlight how microbiota profiling through next-generation sequencing could be used to anticipate bacterial infection diagnosis.

Keywords: Actinomycosis; Allogeneic hematopoietic stem-cell transplant; Oral diseases; Oral microbiota.

Fig. 1

Blood cell counts and antibiotics administered during allogeneic hematopoietic stem-cell transplant (allo-HSCT). A Blood cell counts during allo-HSCT. Blood cell count data was collected at the following allo-HSCT timepoints: D-5 (preconditioning), D5 (aplasia), D21 (engraftment), D50 (~ 4 weeks after engraftment), and D85 (~ 9 weeks after engraftment). Dashed green horizontal lines represent normal reference values. B Antibiotic usage timeline during allo-HSCT. Antibiotics used between stem-cell (SC) infusion and actinomycosis diagnosis: cefepime (cefe) and vancomycin (vanc)

Fig. 2

Different perspectives of oral lesion clinical aspects. A mesial, B vestibulo-mesial, C palatal and D mesio-palatal

Fig. 3

Pathological and molecular studies. A Histological study between the erythematous border and deepithelialization demonstrating inflammatory reaction with lymphocytes and collagen fibres (HE, left × 100 and right × 300); B Histological study in the central portion of the lesion with necrotizing inflammation and accumulation of colonies of gram-positive bacteria (arrow); C Gram stain histology demonstrating positivities for gram-positive bacteria with coccoid-shaped colonies (GS, × 100); D Oral microbiota profiling. Upper graph: alpha diversity (Gini-Simpson index) throughout transplantation and follow-up. Bottom graph: with relative abundance (RA) of the genus Actinomyces. DB dental biofilm, GCF gingival crevicular fluid, OM oral mucosa (HE hematoxylin and eosin, GS gram-staining, NGS next-generation sequencing)

Fig. 4

Study of extranodal NK/T-cell lymphoma markers. Immunohistochemistry method for A–C and, in situ hybridization for viral status. A CD20, B CD3, C CD56 and D Epstein–Barr virus (EBV)