Evaluation of patients with gastrointestinal Histoplasma infection

Posted by Master, Doctor Mai Vien Phuong - Department of Examination & Internal Medicine - Vinmec Central Park International General Hospital

Histoplasma capsulatum (H. capsulatum) var. capsulatum is a dimorphic fungus known to be widespread around the world. The most common presenting symptoms in patients with gastrointestinal histoplasmosis are abdominal pain and inflammatory diarrhea.

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the intestinal mucosa through a complex immune-mediated mechanism. The two main subtypes of inflammatory bowel disease, Crohn's disease and ulcerative colitis (UC), are based on histological involvement of the intestine. Inflammatory diarrhea is a common feature seen in both gastrointestinal histoplasmosis and inflammatory bowel disease. Similarities in presentation, related patterns of the gastrointestinal (GI) tract, and associated inflammation are the reasons gastrointestinal histoplasmosis is considered an inflammatory bowel disease mimic.

Diarrhea is objectively defined as passing stools with a weight or volume greater than 200 g or 200 mL every 24 hours. According to the Centers for Disease Control and Prevention, chronic diarrhea is defined as diarrhea that lasts more than two to four weeks. Initial investigation to evaluate chronic diarrhea begins with history and physical examination to establish a preliminary differential diagnosis. The appearance of stools can be classified into one of three major subtypes for further diagnostic investigation: Malabsorption: The primary investigations in patients with malabsorption diarrhea are aimed at rule out anatomical defects. Radiographic examination of the abdomen, and colonoscopy or colonoscopy with or without biopsy can help diagnose the specific underlying cause. A positive fecal chymotrypsin level confirmed with a positive secrettin test is diagnostic of pancreatic insufficiency. Inflammatory diarrhea: In patients with suspected inflammatory diarrhea, stool analysis is always the initial investigation option. Stool analysis positive for blood, white blood cells, and calprotectin in the stool points to the diagnosis of inflammatory bowel disease. This can be confirmed by colonoscopy and an associated bowel biopsy. In patients with no WBC in the stool and a negative analysis, further investigation is needed to determine the underlying cause. Testing for C. diff has become standard practice in patients with inflammatory diarrhea. The authors strongly support and urge clinicians to test for H. capsulatum, particularly in patients in endemic areas and those with inflammatory bowel disease, because the literature reports a high prevalence of mycosis. Gastrointestinal histoplasma was high in autopsy samples. Watery diarrhea: The primary investigation of choice was fecal osmotic gap measurement. A high stool osmolality gap (>125 mOsm/kg) together with a history of increased diarrhea with consumption of dairy products and a positive hydrogen breath test confirm the diagnosis of lactose intolerance. A normal fecal osmolality gap with improvement in symptoms with dietary changes is commonly seen in patients with irritable bowel syndrome. However, patients who have a normal fecal osmolality gap and do not improve with dietary modification may require further treatment for Celiac disease, including a celiac panel. Patients with a low osmolar gap (<50 mOsm/kg) may require further imaging, blood, and urine tests to investigate other possible causes. It is important to realize that diarrhea is not a disease but a symptom of an underlying medical condition. Patients with ulcerative colitis will have inflammatory diarrhea with the presence of pus and blood on stool analysis. Furthermore, inflammatory bowel disease mimics such as gastrointestinal histoplasmosis may also present with inflammatory diarrhea as shown in the authors' case report. Therefore, it becomes extremely important to distinguish acute exacerbation of ulcerative colitis from other causes to initiate treatment early and prevent adverse outcomes.

Histoplasmosis is an endemic fungal disease caused by a dimorphic fungus called H. capsulatum. Two distinct types of Histoplasma that cause disease in humans include H. capsulatum var. capsulatum is common worldwide in endemic areas, and H. capsulatum var. duboisii is restricted to sub-Saharan Africa. In the United States, endemic areas with high rates of histoplasmosis include concentrated areas in the Ohio and Mississippi River valleys. An analysis of data from hospital records in 2002 found 3370 inpatients and 254 deaths associated with histoplasmosis with nearly 90% of these hospitalizations in the midwest and southern regions of the United States. Ky. H. capsulatum var. capsulatum is dimorphic which means it exists in two distinct forms. It grows as mycelium in soil, bird and bat droppings, but when inhaled the spores convert to the pathogenic yeast form, which multiplies inside macrophages. These macrophages can transport yeast to virtually any organ in the body leading to histoplasmosis.

Although H. capsulatum is non-infectious and humans are a dead or accidental host for the fungus to multiply, it seems to be particularly well-adapted to mammalian host cells. The pathogenic yeast stage is equipped to avoid interstitial killing by macrophages with mechanisms to degrade reactive oxygen species, regulate lysosome pH, and capture essential nutrients that may otherwise be lost. deprive. Human infections caused by H. capsulatum commonly manifest as acute pulmonary histoplasmosis, chronic pulmonary histoplasmosis, cutaneous histoplasmosis, rheumatic histoplasmosis, ocular histoplasmosis, mediastinal histoplasmosis, bronchiectasis, and histoplasmosis. progressive spread to the brain. histoplasmosis is commonly seen in immunocompromised states with low CD4 cell counts (<200 cells/mm3), such as in patients with acquired immunodeficiency syndrome, and also rarely in patients with acquired immunodeficiency syndrome. human T-lymphovirus 1 infection.

Histoplasmosis of the gastrointestinal tract, also known as gastrointestinal histoplasmosis, is a rare entity. Gastrointestinal involvement in histoplasmosis is very nonspecific, can involve any region of the gastrointestinal tract, and is commonly seen in immunocompromised patients. However, the most common sites of involvement are the terminal ileum and colon because of the abundance of lymphatic tissue. Involvement becomes less common near the intestine.
The literature reports a high prevalence of gastrointestinal histoplasmosis in autopsy samples, indicating a higher incidence of asymptomatic disease. The most common presenting symptoms in patients with gastrointestinal histoplasmosis are abdominal pain and diarrhea. This diarrhea may be episodic and typical of other illnesses, or may be unresolved and be related to malabsorption. Bloody diarrhea may also be present in a small group of patients with gastrointestinal histoplasmosis and often mimics inflammatory bowel disease, making it difficult to distinguish between inflammatory bowel disease and gastrointestinal histoplasmosis.

Other symptoms associated with gastrointestinal histoplasmosis may include unusual fever with or without chills and night sweats, loss of appetite, varying degrees of weight loss, and abdominal distention. On physical examination, the patient may have hepatosplenomegaly, peripheral lymphadenopathy, abdominal pain, and rebound pain associated with peritonitis. Similarities in presentation, gastrointestinal involvement patterns, and associated inflammation are the reasons why gastrointestinal histoplasmosis is considered a mimic of inflammatory bowel disease.

Laboratory studies in patients with gastrointestinal histoplasmosis may show increased levels of alkaline phosphatase, lactate dehydrogenase, and increased levels of inflammatory markers such as ESR, CRP, and serum ferritin levels. bar. In the case of the authors, all liver enzymes were reported with increased ESR and CRP. Leukopenia may indicate underlying immunodeficiency. Although none of these studies were diagnostic of H. capsulatum, they do instruct physicians to consider infectious etiology as a differential diagnosis for current symptoms. For patients with suspected histoplasmosis, serum and urine Histoplasma antigen immunoassays should be performed. The urine antigen-enzyme immunoassay has high sensitivity (89.47%) and specificity (100%) in detecting H. capsulatum.
Radiation studies such as CT scans and magnetic resonance imaging can also help doctors diagnose gastrointestinal histoplasmosis and rule out other causes of bloody diarrhea. Radiographic findings with gastrointestinal histoplasmosis may include: Thickening of the intestinal wall; Massive lesions of the intestine; Signs suggestive of small bowel obstruction; Intestinal perforations, although rare, may show free intraperitoneal air; hepatosplenomegaly; whole body lymphadenopathy.

The most common endoscopic findings in patients with gastrointestinal histoplasmosis are single or multifocal mucosal ulcers. Polyps, constrictions, and obstructions may also be noted. A definitive diagnosis of gastrointestinal histoplasmosis is always established by colonoscopy and biopsies of lesions may show the typical 2 to 4 micron yeast structure of H. capsulatum.
Although histopathological specimens of the fungus can be stained with hematoxylin and eosin, better visualization can be achieved using silver methenamine or periodic acid-schiff staining. There should also be evidence of a culture of H. capsulatum for diagnosis. However, in the case of the authors, a colonoscopy with biopsy was recommended for the patient, who declined the procedure because he had had a colonoscopy with biopsy 10 months prior to the determination. diagnosed with ulcerative colitis and do not want to repeat the procedure. After learning of a positive urine antigen test result for H. capsulatum and that gastrointestinal histoplasmosis may resemble an exacerbation of ulcerative colitis, the patient wishes to continue treatment for histoplasmosis. gastrointestinal tract and postpone the procedure to a later date, if applicable. did not improve his symptoms.

Conclusion
The most common presenting symptoms in patients with gastrointestinal histoplasmosis are abdominal pain and diarrhea. Gastrointestinal histoplasmosis often mimics inflammatory bowel disease due to similarity in presentation, related pattern of gastrointestinal tract, and associated inflammation. Therefore, for patients with inflammatory diarrhea, or those with diagnosed inflammatory bowel disease with clinical features of a possible exacerbation without an underlying cause, gastrointestinal histoplasmosis should be among the differential diagnoses. The diagnosis of gastrointestinal histoplasmosis was confirmed by colonoscopy and biopsies of the relevant area of ​​the gastrointestinal tract. The treatment for histoplasmosis depends on the severity of the disease.