Statistics from Altmetric.com
A 21-year-old immunocompetent female hailing from a rural eastern Indian village, farmer and cattle herder by profession, presented with several asymptomatic lumps and bumps over her neck. It had started developing as a solitary pea-sized swelling on the neck which gradually progressed over 2 years to involve the entire front of neck and lower jaw. There was no history of discharge, similar swelling elsewhere or any family history of such lesions. In the same duration, a cow in her farm had been afflicted with a similar nodulocystic cutaneous predicament and died a few weeks prior to present consultation. However, no specific diagnosis could be reached by treating veterinarian. Cutaneous examination revealed a 16×8 cm hyperpigmented plaque studded with skin coloured to brownish-black papules and nodules overlying the anterior neck and submandibular area. Few clear fluid-filled cysts which demonstrated positive transillumination test were also noted (figure 1A). Examination of patient’s other mucocutaneous sites, regional lymph nodes and organ systems did not reveal anything unusual.
Her baseline laboratory investigations revealed mild anaemia. No bony involvement was noted on X-ray of chest and mandible. Skin biopsy from a representative nodule revealed sulphur granules surrounded by neutrophils in an area of granulation tissue, further encased by filamentous gram-negative bacillary structures (figure 1B,C). Fungal staining and modified Ziehl-Neelsen stain (1%) was negative. Culture of fluid aspirate from cyst grew out Actinobacillus lignieresi, sensitive to tetracycline. The material and isolated bacterial colonies were also positive in PCR for ribosomal RNA gene 16S for A. lignieresi. Based on these findings, a diagnosis of cutaneous actinobacillosis was established. She was started on tablet doxycycline 100 mg two times per day; significant lesional resolution with resultant scarring was seen after 4 weeks (figure 1D). This therapy was continued for another 3 months based on clinical and therapeutic response. No recurrence was observed on 6 months follow-up.
Lignieres and Spitz first described actinobacillosis as a cattle infection with subsequent reports in sheep and dogs. It is an aerobic, non-spore forming, gram-negative oval to rod-shaped coccobacilli, widespread in soil and colonises as normal flora in the upper gastrointestinal and respiratory tracts of ruminants.1 2 In infected animals, there is a tendency to invade the soft tissues of the oropharynx and skin causing granulomatous or pyogranulomatous lesion of subcutaneous tissues in the head and neck region, along with secondary involvement of the adjacent lymph nodes, lungs, abdominal and pelvic viscera.
Human infection with actinobacillosis has rarely been documented. On literature review, we came across 10 documented cases of human infection with actinobacillosis (all of them had internal organ involvement).3 4 Interestingly, isolated cutaneous involvement as seen in our patient has not been reported previously.
Actinomycosis is a very close differential of this condition often leading to diagnostic dilemma.5 A. lignieresi forms large basophilic colonies with long, thin radiating clubs. Actinomyces are filamentous, gram-positive, non-acid fast, microaerophilic to anaerobic bacteria. While actinobacillosis commonly arises in the soft tissues, actinomycosis usually affects the hard tissues. Given the contact of the patient with cows and sheep, an exogenous origin either through a skin wound or indirect contamination was suspected in our patient. There are limited data regarding the effective treatment of A. lignieresi infection in human. Sodium iodide and tetracycline are effective in treating the disease. Surgical debridement may be considered in cases where there is inadequate response to medical therapy.3 6
Actinobacillosis is mainly a zoonotic disease affecting cattle, sheep and horses. Human infection has rarely been reported. Isolated cutaneous affection without underlying organ involvement is an uncommon presentation.
The combination of specific exposure and clinical pattern should induce a high index of suspicion regarding this rare infective condition.
Actinomycosis serves as an important differential and must always be ruled out.
Contributors AS and UC contributed to conception, initial drafting of manuscript, critical revision of content and final approval of manuscript. IS and AC contributed to patient management, conception, critical revision of content and final approval of manuscript. All authors are in agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.