A 71-year-old Japanese man, with a medical history of hypertension and surgical treatment of left (age, 61 years) and right (age, 70 years) inguinal hernias, experienced swelling and pain in the region of his left inguinal incision. He visited a local hospital 6 days after symptom onset. An incarcerated hernia was suspected, and the patient was referred to a surgeon at our hospital the next day. His vital signs were unremarkable and he was afebrile. A physical examination revealed tenderness and swelling in the left inguinal region, where elastic, hard masses were palpable. Blood tests showed leukocytosis (8350/microL; normal range, 3500-8000/microL) and an elevated C-reactive protein level (10.19 mg/dL; normal, <0.16 mg/dL). Abdominal to pelvic computed tomography revealed a left inguinal hernia and confirmed 5-6 swollen left inguinal lymph nodes (Fig. 1), with maximum sizes of 1-4 cm. The soft tissue surrounding the swollen lymph nodes showed increased computed tomography density, but swollen lymph nodes were not found in other areas, including in the right inguinal region (Fig. 1). Therefore, infectious lymphadenitis of the left inguinal lymph node was suspected. The patient was referred to a plastic surgeon on the same day. Mucosal or cutaneous lesions were not found on the penis, scrotum, or the left lower limb, making metastatic carcinoma unlikely. The swollen lymph nodes were biopsied for bacteriological testing and pathological diagnosis. Upon biopsy, the swollen lymph nodes were fragile and discharged pus. Thus, the lymph nodes were partially resected. Bacterial examination of the pus failed to reveal the presence of microorganisms.
The main histological finding in the resected lymph node was the presence of an abscess and suppurative lymphadenitis. The lymphoid follicles were inconspicuous, and multifocal abscesses were noted in the central portion of the lymph node (Fig. 2A, B). The lymph node capsule was inconspicuous and might have been replaced by suppurative inflammation or suppurative exudate (Fig. 2A, C). Dense fibrosis was not observed in the peripheral region of the lymph node. Many histiocytes had infiltrated the lymph node and several vague granulomas were suggested (Fig. 2D). The suppurative granulomas might have been present because of the dense histiocytic infiltrates around some abscesses. A few multinucleated histiocytes (Fig. 2B, inset) were observed in one abscess. The lymph node cortex consisted mainly of lymphocytes and plasma cells associated with proliferating vessels, suggestive of marked interfollicular hyperplasia (Fig. 2E). Plasma cells were located around the vessels (Fig. 2E), but did not show a sheet-like arrangement. Neutrophils were present in many vessels, suggesting endoarteritis (Fig. 2F) and phlebitis. Suppurative (granulomatous) lymphadenitis was observed in the lymph node.
Bacterial, fungal, and mycobacterial infections were considered, with syphilitic infection and cat scratch disease included in the differential diagnoses. Gram, periodic acid-Schiff, and Ziehl-Neelsen stains failed to confirm the presence of microorganisms; however, some spiral microorganisms were suggested by Warthin-Starry staining. Immunohistochemically, numerous spiral microorganisms, positive for anti-Treponema pallidum polyclonal antibodies (1:800; Abcam, Cambridge, UK), were confirmed. The microorganisms were mainly present around or in the walls of the proliferating vessels (Fig. 3A-C) and were scattered throughout the suppurative areas. Negative results were found in the sections stained with anti-bacille Calmette-Guerin polyclonal antibodies (1:1000; DAKO, Glostrup, Denmark), anti-mycobacterial tuberculosis polyclonal antibodies (1:800; Abcam), and antibodies reactive to Bartonella henselae proteins (1:50; lone H2A10, Biocare Medical, Pacheco, CA). Therefore, syphilitic lymphadenitis was strongly suggested.
After the pathological diagnosis, the patient met with a dermatologist, approximately 2 weeks after symptom onset. The medical interview revealed that the patient had engaged in sexual intercourse with a woman at a brothel approximately 2 weeks before symptom onset. His physical examination had not shown any skin lesions, and he had not noticed cutaneous itching or lesions following the presumed day of infection. Serological tests for rapid plasma regain (RPR, 75 RU; normal, 0-0.9 RU) and the T pallidum hemagglutination assay (32; normal, <1.0) were both positive; anti-human immunodeficiency virus antibodies were not detected. Therefore, the patient was diagnosed with primary syphilis.
The patient was treated with oral amoxicillin (1.5 g/d) for 4 weeks, resulting in his RPR titer decreasing to 34 RU. An additional 2 weeks of antibiotic therapy resulted in successful treatment, as indicated by a further 4-fold reduction in RPR titer (to 6.9 RU). During this time, the left inguinal lymph nodes became non-palpable.
The patient provided written consent for the publication of this report.