Unusual Behavior of Intestinal Spirochetosis: A Case Report

Abstract

Human intestinal spirochetosis is a rare clinicopathological condition characterized by the presence of spirochetal microorganisms on the surface of the colorectal mucosa and, in some cases, by their invasion into the lamina propria. The most frequent cause of this infection is immunocompromised status. Our case report describes a patient with relevant symptoms and endoscopic alterations, but limited invasion by spirochetes, as shown by histological analysis of ileal and colonic specimens. After histological examination, metronidazole was initiated. This resulted in rapid and complete resolution of the symptoms, which demonstrated an infectious etiology. The peculiarity of our case is that the clinical and endoscopic appearances were typical of the aggressive behavior of the disease, but histological samples showed only superficial colonization of the colonic epithelium without clear invasion of deeper layers. This case report emphasizes that the virulence of spirochetes is not strictly related to intestinal mucosal invasion.

1. Introduction

Human intestinal spirochetosis (HIS) is a rare clinicopathological condition characterized by the presence of spirochetal microorganisms on the surface of the colorectal mucosa and, in some cases, by their invasion into the lamina propria. In developed countries, the incidence of HIS is low, and the most typical manifestation is rectal involvement in patients infected with HIV.^[1]

The diagnosis of intestinal spirochetosis is usually incidental and based on histological samples obtained during screening colonoscopy. The most common symptoms include chronic watery diarrhea and vague abdominal pain.^[2] The endoscopic appearance of HIS needs to be differentiated from that of inflammatory bowel disease^[3] because it can rapidly become fatal.^[4–10]

In patients with gastrointestinal symptoms associated with intestinal spirochetosis, we used histological samples to observe the invasion of spirochetes into the epithelial layer up to the lamina propria. When this infection is asymptomatic, the localization of the spirochetes is usually on the surface of the epithelium.^[2]

2. Case presentation

A 41-year-old man was admitted to the Fondazione Poliambulanza Hospital from December 14, 2016, to December 20, 2016, for persistent mild hypogastric pain, severe perianal pain, and hematochezia with mucus. Medical history was unremarkable, except for an occasional headache, which was treated with nonsteroidal anti-inflammatory drugs on demand. The patient had not recently traveled to any at-risk countries, nor did he have a history of homosexual behavior, illicit drug use, or HIV infection or other immunodeficient conditions.

Upon admission, his vital signs were stable, with a body temperature of 36.2°C and mild tachycardia. Chest radiography, abdominal radiography, and abdominal ultrasonography were unremarkable. The microbiological and parasitological results of a stool culture test were negative, and HIV serology was negative. Blood examinations revealed the following: Hb, 14.3 g/dL; mean corpuscular volume, 84.4 fL; platelets, 192 × 10³/μL; white blood cells, 7.07 × 10³/μL (neutrophils, 62.2%; lymphocytes, 26.1%; monocytes, 7.9%; and eosinophils, 3.5%). Inflammatory markers were elevated (C-reactive protein, 8.8 mg/L; normal value, <0.5 mg/L; and fecal calprotectin, 667 mg/kg). Intravenous paracetamol 1000 mg was administered, and there was partial improvement in pain. Colonoscopy revealed multiple erosions and aphthae in the sigmoid colon and terminal ileum.

Because of suspicion of inflammatory bowel disease, mesalazine treatment was started.

Histological examination showed an increase in chronic inflammatory cells with eosinophilic infiltration, with no glandular crypt distortion, follicular lymphoid aggregate, or basal plasmacytosis. However, a thick brush border was observed on the superficial epithelium [Figure 1A], whereas Warthin-Starry and Giemsa staining [Figure 1B] was positive for spirochetosis localization in both ileal and colonic specimens. Morphology was suggestive of intestinal spirochetosis (in the literature, the most represented subspecies in humans are Brachyspira alborgi and Brachyspira pilosicoli, but we did not characterize our spirochetes in terms of subspecies analysis because of laboratory limitations). Bacteria were allocated to the apical cell membrane of the colorectal epithelium, with only focal permeation into the cellular layer of the surface epithelium and no invasion of the lamina propria.

Figure 1.

Histological examination in the colonic specimens (original magnification × 400). Hematoxylin-eosin (A) and Warthin-Starry and Giemsa staining (B) showing eosinophilic infiltration and a thick brush border with a positive finding for intestinal spirochetosis.

Mesalazine was discontinued and intravenous metronidazole was initiated. After a few days, the patient improved clinically and was discharged. Ten days later, complete resolution of the symptoms was confirmed.

Written informed consent to publish the clinical information in the journal was obtained from the patient.

3. Discussion

Intestinal spirochetosis is uncommon in developed countries and is usually associated with specific risk factors (ie, traveling to undeveloped countries, HIV infection, immunocompromised state, and childhood).^[10]

This condition is often asymptomatic,^[1,2,9] and the diagnosis is often incidental in histological samples. In patients who are asymptomatic, spirochetes are detected on the surface of the colonic mucosal epithelium. In patients with more advanced symptoms, the penetration of spirochetes in the colonic wall is typically associated with the presence of gastrointestinal symptoms.^[10]

The peculiarity of our case is that clinical and endoscopic observations resembled the aggressive behavior of the infection typically seen in childhood manifestations. However, histological samples showed only superficial colonization of the colonic and ileal epithelium without clear invasion of deeper layers, which is in contrast to other cases described in the literature.^[10] Our case report emphasizes that the virulence of spirochetes is not strictly related to the invasion of the intestinal mucosa. In addition, our patient had no risk factors, such as immunodeficiency or HIV infection, unlike most cases described in the literature.

Conflicts of Interest

None.

Data Availability Statement

The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.