근간 Gastroenterology News에 분선충증 증례가 소개되었기에 옮깁니다.
Researchers describe a nearly missed case of Strongyloides infection in the April issue of Gastroenterology, had it not been for analysis of duodenal biopsies.
Douglas Grunwald et al describe the case of a 74-year-old Jamaican-born woman with a 3-month history of dyspepsia, nausea, bloating, early satiety, and weight loss of 40 lbs. In the past, she had been infected with Helicobacter pylori and Strongyloides, both of which were treated; she also had a history of acid reflux, diabetes, and hypertension. Her medications included metformin, simvastatin, and losartan. An abdominal computed tomography (CT) scan showed signs of endometrial cancer. She subsequently had an uncomplicated abdominal hysterectomy. However, she continued to have nausea, anorexia, and failure to thrive. On readmission to the hospital 15 days after surgery, a CT scan showed small bowel hyperenhancement, edema, and anasarca. Tests of stool for Strongyloides ova, parasite, and antibodies all gave negative results.
The physicians performed an esophagogastroduodenoscopy and found large, geographic duodenal ulcers with brownish discoloration of the mucosa (arrows in figure A). She had not used nonsteroidal anti-inflammatory drugs and tested negative for H pylori. Duodenal biopsies revealed parasitic forms consistent with Strongyloides species (figure B). Strongyloides is a soil-transmitted helminth - its primary mode of infection is through contact with soil that is contaminated with free-living larvae. When the larvae come in contact with skin, they penetrate it and migrate through the body, eventually finding their way to the small intestine, where they burrow and lay their eggs. Unlike other soil-transmitted helminths like hookworm or whipworm, whose eggs do not hatch until they are in the environment, the eggs of Strongyloides hatch into larvae in the intestine. Most of these larvae are excreted in the stool, but some of the larvae molt and immediately re-infect the host either by burrowing into the intestinal wall or by penetrating the perianal skin.
Gastrointestinal manifestations of Strongyloides infection include nausea, vomiting, anorexia, abdominal pain, and protein-losing enteropathy. Patients are usually treated with anti-helminth drugs (eg, ivermectin, albendazole). The researchers say that they did not have positive results from stool studies or ELISAs for Strongyloidesserum antibodies because the sensitivity of repeated stool evaluation is around 50%, and sensitivity of the ELISA test is 65%-90%. Furthermore, the antibodies are often not detected in immune-compromised patients. Grunwald et al state that the best way to detect this infection is by histopathology analysis of duodenal biopsies. The endoscopic features of duodenal Strongyloides infection are broad and include edema, brown discoloration of the mucosa, erythema, subepithelial hemorrhages, and megaduodenum. These features are nonspecific and are also seen in patients with ischemic ulcers, users of nonsteroidal anti-inflammatory drugs, or patients with cancer or H pylori infection. Due to the patient's history of previous Strongyloides infection, the authors began treating her with ivermectin before pathologic confirmation of the parasite.
Grunwald et al say that the severity of the patient's illness was likely precipitated by her recent malignancy and a new diagnosis of human T-lymphotropic virus (HTLV-1) infection, which is endemic to the Caribbean and commonly observedin combination with Strongyloides. The authors propose that HTLV-1 disrupts the ability of T cells to detect and eliminate Strongyloides. The patient was treated successfully with an extended regimen of ivermectin and nutritional support. Four months after treatment, her weight was stable, her albumin level increased, and a repeat esophagogastroduodenoscopy showed normal duodenal mucosa.
분선충(Strongyloides stercoralis)은 특이한 선충입니다. (1) 인체감염 선충 중 그 크기가 가장 작습니다. mm 단위 이하입니다. (2) 자유생활세대 (free-living generation)를 가집니다. 즉 흙에서 스스로도 잘 살아갑니다. (3) 피부를 통해 침입합니다. (4) Autoinfection이 가능합니다. 대부분의 선충은 충란 하나를 먹으면 몸 속에 한 마리의 기생충이 생깁니다. 그러나 분선충은 인체의 면역력이 약하면 자가감염을 통하여 무한증식할 수 있습니다. 기생충이 무한증식하니 환자가 죽게되는 것입니다. Autoinfection 때문에 환자가 죽을 수 있는 또 다른 기생충은 장모세선충 (Capillaria philippinensis)입니다.
가장 중요한 특징은 크기가 작다는 것입니다. 거의 눈에 보이지 않습니다. 0.5-2mm 크기이면서 매우 가늘기 때문입니다. 회충은 30cm이고 요충이나 편충은 2-4cm 라는 것을 생각해 보면 얼마나 작은지 알 수 있습니다. 아래 그림에서 그 크기를 비교해 보십시요. 분선충이 눈에 보이기나 합니까? 따라서 크기로 대강 감별할 수 있습니다.