CASE REPORT
A 55-year-old Indigenous Australian male living in remote Central Australia was admitted to Alice Springs Hospital in December 2015 for pain and swelling at the right calf resulting in a limp. For context, Central Australia is a rural region of over 1,000,000 km2 comprising approximately 10% of the total Australian landmass (Figure 1). It is sparsely populated by about 60,000 people.(4) Of these, approximately 40% are Indigenous Australians who are more likely to suffer from numerous chronic diseases and have poor health literacy than their non-Indigenous counterparts.(5) Alice Springs Hospital is the referral facility for this vast remote area.
The patient’s relapsing-remitting symptoms had begun in 2012 following a fall which, according to him, did not cause traumatic injury or skin penetration. He was reviewed in the Orthopaedic clinic in 2014 where he was noted to have an antalgic gait with a range of motion at the right knee of 90-140° and crepitus on movement, and a palpable medial gastrocnemius lesion. MRI of the right leg showed heterogeneous thickening of the medial gastrocnemius/soleus measuring 35×28×147 mm with unusual tubular extension into the central aspect of the medial gastrocnemius favouring post-injury haematoma, but raising the possibility of a neoplastic process (Figure 2). Unfortunately, he was lost to hospital follow-up until October 2015 when a further Orthopaedic outpatient review showed no change in the morphology or character of the lesion and continued observation was recommended.
His past medical history included poorly-controlled type 2 diabetes mellitus complicated by macroalbuminuria, hypertension, hyperlipidemia, obesity, complete heart block requiring pacemaker insertion, osteoarthritis of the right knee and left shoulder, and right leg varicose veins. His regular medications were aspirin 100 mg daily, atorvastatin 40 mg daily, gliclazide MR 120 mg daily, metformin XR 2 g daily, perindopril/indapamide 10/2.5 mg daily, sitagliptin 100 mg daily, and tadalafil 20 mg as required. On examination at the time of admission, there were distended superficial veins below the knee, and marked hard swelling and tenderness of the ankle and right calf to the level of the popliteal fossa. He was afebrile with a pulse rate of 96, respiratory rate of 22, blood pressure of 99/90 mmHg, and oxygen saturation of 97% breathing air on admission. C-reactive protein was raised at 177 mg/L (normal range 0-5), as he had a neutrophil leukocytosis with total white cell and neutrophil counts of 16.3×109/L (4-11) and 10.4×109/L (2.0-7.5), respectively.
A CT scan was performed to characterize the lesion further. This again showed a cystic morphologically heterogenous structure, but also that it had increased in size to 38×49×156 mm with a larger solid component, again raising the possibility of sarcoma (Figure 3). This differential diagnosis was also supported by the peripherally-enhancing, multi-loculated nature of the lesion. The patient remained an inpatient under the General Surgical team for three days, where he received empirical cefazolin 1 g eight-hourly. Aspiration of the lesion for histological and microbiological examination was planned, but deferred by the patient to February 2016 when it was performed under ultrasound guidance.
The aspirate demonstrated an inflammatory exudate comprising primarily neutrophils and pigment-laden macrophages compatible with abscess. No malignant cells were seen, but culture yielded pure growth ofPantoea spp. susceptible to amoxicillin/clavulanate, cefazolin, ciprofloxacin, gentamicin, and trimethoprim/sulfamethoxazole but resistant to ampicillin. Identification to species level was precluded by laboratory technological limitations but, given the culture result, the patient was referred to the Infectious Diseases clinic where he was seen in April 2016. He reported never feeling systemically unwell or febrile, and that, subsequent to the aspiration, the pain and swelling had improved to the extent he was able to walk normally. The calf mass remained palpable and hard to touch (Figure 4), but CRP had decreased to 11 and he no longer had a leukocytosis. Investigations for immunodeficiency revealed no lymphocyte deficiency and negative serology for HIV and Strongyloides , but he was infected with HTLV-1, in keeping with the very high prevalence in Indigenous Central Australians.(6) A detailed occupational and exposure history was taken, in which he denied performing agricultural work or gardening in the course of his work as an Aboriginal Health Worker or recreationally, but for cultural reasons would go into the desert surrounding his rural community when required.
To confirm that the lesion was, indeed, an abscess a second aspiration and tissue core biopsy was performed. Again, no malignant cells were seen and pure growth of Pantoea spp. was cultured. Insufficient tissue was obtained to draw a definitive histological conclusion, but the patient refused a second attempt as well as any surgical intervention. As such, he was commenced on amoxicillin/clavulanate 875/125 mg in May 2016 for six weeks, ciprofloxacin being contraindicated because of his history of arrythmia.
Despite successful completion of antibiotic therapy, the lesion was still obvious at follow-up in October 2016 and the patient reported similar symptom exacerbations in the preceding months which would spontaneously resolve. His case was, thus, discussed at a specialist sarcoma multi-disciplinary meeting where the consensus opinion was that an abscess, rather than malignancy, was the most likely diagnosis. Ongoing surveillance with imaging was recommended but the patient was lost to follow-up until 2020, when an ultrasound scan requested by his general practitioner showed persistence of the mass which had organized into three separate collections measuring 150×25mm, 27×10 mm, and 31×28 mm. The patient declined further intervention for this problem and, at the time this report was written in 2022, remained systemically well. Apart from the six weeks of amoxicillin/clavulanate commenced in 2016, he had not had any extended antibiotic courses for the abscess.