A 28-year-old-male, case of mucinous adenocarcinoma rectum (cT3N0), post-neoadjuvant radio-chemotherapy (capecitabine), and surgery (laparoscopic abdominoperineal resection) with an end-sigmoid stoma in left iliac fossa, presented with painful peristomal ulcer of five months duration [Figure 1]. It started as redness in peristomal location two months post-surgery and progressed to form a painful ulcer over next one month. Multiple courses of oral/topical antibiotics and antiseptics were given with minimal response. There was no other comorbidity.
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Figure 1: Peristomal ulcer with gray-white necrotic base and surrounding erythema
On examination, a single 8-cm-diameter ulcer with grayish white necrotic slough was present in peristomal region, surrounded by ill-defined erythema and hyperpigmentation with mild tenderness and induration. Routine hematological and biochemical investigations including fasting blood glucose levels were normal. Viral markers for HIV, Hepatitis B, and Hepatitis C were negative. Pus swab and culture, tissue specimen for bacterial culture, fungal culture, and Mycobacterium CBNAAT were negative.
Pathology
Punch biopsy of the skin taken from the edge of ulcer revealed ulcerated epidermis covered with sheets of large round to oval cells with eccentric nucleus and ingested red blood cells [Figures 2 and 3]. The dermis showed granulation tissue with dense lympho-plasmacytic infiltrate with few neutrophils and eosinophils. Periodic acid–Schiff stain highlighted the large cells [Figure 4].
Figure 2: Ulcerated epidermis covered with sheets of large round to oval cells and granulation tissue in the dermis (H and E, 100×)
Figure 3: Large round to oval cells with abundant granular eosinophilic cytoplasm, eccentric nucleus, and ingested red blood cells (black arrow) covering the epidermis (H and E, 400×)
Figure 4: Periodic acid–Schiff stain highlighting the large round to oval cells covering the ulcerated epidermis (PAS, 400×)
What is the diagnosis?
Answer
Peristomal cutaneous amoebiasis. The patient was started on oral metronidazole 400 mg thrice a day and the lesion healed completely over next 3 weeks [Figure 5].
Figure 5: The lesion healed completely after 3 weeks of metronidazole therapy. Healthy pink stoma can be seen in center
Discussion
Amoebiasis is primarily a gastrointestinal infection caused by protozoa Entamoeba histolytica. It spreads via feco-oral route and the ingested cysts transform into trophozoites in colon, resulting in luminal amoebiasis (asymptomatic carriers) in majority of the cases and colitis (abdominal pain, dysentery) in symptomatic cases. Rarely, it may affect the extra-intestinal organs including liver, lungs, heart, brain (hematogenous spread), and perianal/vulvar/peristomal skin (contiguous spread).[1,2] Tissue lysis mediated by proteolytic enzymes released by trophozoites is the primary pathomechanism. The cutaneous manifestations include painful ulcers, verrucous plaques, and subcutaneous nodules. The ulcer morphology by itself is non-diagnostic, but usually has gray-white necrotic slough, irregular margins with hyperkeratotic undermined edges, and surrounding erythema. The skin lesions are usually destructive and rapidly progressive, and the duration may vary from less than 2 weeks to as long as 2 years.[1] The trophozoites can be identified on histology as round or oval organism measuring 20 to 50 μm with abundant finely granular eosinophilic cytoplasm, eccentric nuclei, prominent nucleoli, and erythrophagocytosis (hallmark of pathogenic Entamoeba, differentiates from non-pathogenic strains).[3] Periodic acid–Schiff stains the glycoprotein containing cell membrane of the organism.
Peristomal skin complications are common in stoma patients with reported prevalence of 73%.[4] These can interfere with adhesion of stoma appliance and result in morbidity, thereby necessitating early diagnosis and management. The predisposing factors include constant moisture due to contact with fecal matter, prolonged occlusion due to appliance, repeated microtrauma while changing stoma appliance, and vulnerable skin due to surgical trauma.[5] The underlying pathophysiology could be damage to cutaneous nerves resulting in disturbed neuro-immune balance and local lymphatic drainage at the surgical site. This results in defective epidermal barrier function, akin to the formation of postsurgical immunocompromised district which predisposes to various dermatoses like eczema, pyoderma gangrenosum, vitiligo, not only in immediate postsurgical period but even several years later.[6] In our case, subclinical intestinal amoebiasis and site-related moisture in the postsurgical immunocompromised district could have facilitated amoebic invasion and ulcer formation two months post-surgery.
Peristomal amoebic ulcer can result from shedding of intestinal trophozoites onto the continuous skin. The demonstration of motile trophozoites on wet mount preparation and erythrophagocytosis on histology is diagnostic. Fresh material from the edge of lesion (avoiding the necrotic tissue) should be taken for microscopic examination. History of dysentery and the presence of trophozoites in stool are contributory, though not essential to the diagnosis of cutaneous amoebiasis. Due to low yield, multiple stool examinations are recommended. In our case, there was no history of diarrhea or dysentery, wet mount preparation was negative, and stool examination done for three consecutive days did not show cysts/trophozoites. Newer tests with improved sensitivity and specificity include stool antigen detection, serology, culture, and polymerase chain reaction, but could not be done due to non-availability/financial constraints. Metronidazole is the drug of choice for amoebiasis.
The differentials include contact dermatitis (irritant/allergic), other infections (candida/staphylococcal/streptococcal cellulitis), localized pemphigoid, pyoderma gangrenosum, overgranulation, and malignancy. A similar case of peristomal amoebic ulcer developing four days post-cystohysterectomy and colostomy performed for bladder carcinoma was reported.[5] This entity is rare in modern era owing to routine use of metronidazole in postoperative period and improved patient education regarding hygiene; or perceivably under-reported. The case is reported to underscore the need to suspect this rare but easily diagnosable and treatable condition in a patient presenting with peristomal ulcer, irrespective of interval post-surgery. Improved hand hygiene and eating well-cooked food could be preventive.
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Conflicts of interest
There are no conflicts of interest.
References
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