A Rare Histopathological Finding of Aspergillus Fruiting Bodies in the Knee Joint of an Immunosuppressed Patient

A 30-year-old woman visited the orthopaedics outpatient department with bilateral knee swelling and pain that began during her pregnancy 8 years ago. She consulted many physicians and underwent repeated biopsies that yielded only fibroadipose and fibrocollagenous tissue with no synovial lining. Ultimately, she was diagnosed with systemic lupus erythematosus and was begun on low-dose steroids (6.5 mg/day) at a private set-up 1 year ago. However, following the last biopsy 1 year previously, she developed joint redness, tenderness and subsequently, a discharging sinus at the site of biopsy and developed fever, which did not respond to antibiotics. Her erythrocyte sedimentation rate was mildly raised (22 mm/h); however, no specimen for culture was sent at the time. She was then referred to our centre, where joint debridement was done and histopathological evaluation revealed septate fungal hyphae with acute angle branching, resembling the morphology of Aspergillus with the presence of fruiting bodies in the fibroadipose and fibrocollagenous tissue [Figure 1]. This was confirmed with Periodic Acid Schiff and Silver methenamine stains. No synovial lining or tissue reaction was noted, probably due to the repeated joint debridement performed in this patient. The patient was hence treated with oral itraconazole 200 mg/day for 2 weeks along with surgical debridement. The patient recovered well and is currently being followed up.Figure 1: Photomicrographs of sections taken from the tissue sent after debridement showing fibrocollagenous and fibroadipose tissue with many Aspergillus fungal hyphae and conidial heads ([a] H and E, ×100; [b and c] Periodic Acid Schiff stain, ×100 and ×400)Aspergillus is a ubiquitous saprophytic fungus that usually infects humans via inhalation and causes localised, focal infections in the lung.[1] Fruiting bodies of Aspergillus, on the other hand, are found only in areas of high oxygen tension such as pulmonary cavities, skin and bronchial mucosa.[2] However, isolating them on histopathological sections, particularly from the joint, is very rare.[3] Joint aspergillosis is rare and poorly understood, typically affecting immunocompromised patients. It can be primary, involving skin injury sites like intravenous catheter areas, trauma, adhesive dressings, burns, surgery or secondary, spreading from underlying infections or via vascular spread.[4] Though culture remains the gold standard for detection of Aspergillosis, blood cultures, particularly, have low sensitivity.[3,5] Histopathological detection of the fungus, thus, allows for an early and definitive diagnosis of Aspergillosis.[3] Repeated trauma to the joint site in our patient, immunosuppression along with repeated invasive investigations, use of adhesive dressings and poor maintenance of asepsis by the patient may have led to the inoculation of the fungus in our case. Further, repeated biopsies from the same site at various centres may have allowed for the creation of a region of high oxygen tension due to the formation of a wound tract, allowing the proliferation of characteristic conidial forms of Aspergillus. The Aspergillus fruiting body is composed of a vesicle surrounded by 1 or 2 layers of phialides that produce conidia. Although sporangiophores may be seen in mucor, however, they are not true fruiting bodies with distinct morphology and usually are associated with characteristic broad, aseptate hyphae. Pseudohyphal fruiting bodies have also been described with cryptococcus, coccidioides and blastomyces. However, they lack the true multicellular structure of a fruiting body and are also surrounded by budding yeast forms. The knowledge of the morphology of these is essential for early and accurate diagnosis. Thus, while repeated testing and invasive procedures may be necessary for adequate treatment of a patient, maintenance of asepsis, knowledge of possible complications and proper patient-counselling regarding wound care remain essential, particularly in immunosuppressed individuals. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.