Pleurostomophora richardsiae – an insidious fungus presenting in a man 44 years after initial inoculation: A case report and review of the literature

1The University of Ottawa, The Ottawa Hospital, Ottawa; 2Mount Sinai Hospital; 3University of Toronto; 4Public Health Laboratories, Department of Laboratory Medicine and Pathobiology, Toronto; 5Lakeridge Health, Oshawa, Ontario Correspondence: Dr Jeremy Levenstadt, 95 Bayly Street West, #200, Ajax, Ontario L1S 7K8. Telephone 647-404-5545, fax 905-686-9222, e-mail jeremy.levenstadt@gmail.com case presentation A 54-year-old man from Guyana presented with a painful, nonerythematous, subcutaneous nodule on his right patella at the site of a remote injury. The patient fell while climbing a coconut tree at 10 years of age, 44 years before presentation. The fall caused him to land on the stump of a ‘black sage tree’ injuring his right patella. Multiple small splinters from the stump penetrated his skin over and around his patella, which were removed shortly after the initial injury. The patient reported a significant amount of purulent discharge that eventually subsided. He was never treated with antibiotics. For approximately the next 40 years, the patient reported a history of knee swelling that dramatically increased in recent years. He reported no recent trauma. He experienced no fever, chills, sweats or recent weight loss. The patient was a nonsmoker, did not drink alcohol and had no history of injection drug use. On examination, he was afebrile and looked well. There was no lymphadenopathy. There was a 4 cm × 4 cm nonerythematous, indurated nodule on the anterior aspect of the right patella. There was no joint effusion; however, there was a prepatellar bursitis. The lesion was not adherent to the patella and moved freely. Complete blood count, glucose level, renal function, hepatic transaminases and serum protein electrophoresis were all normal. He was HIV seronegative. A radiograph of the right knee did not demonstrate any foreign body or bone destruction. The prepatellar fluid was aspirated, producing thick fluid, tan-red in colour. Cytological analysis of the fluid showed histiocytes with inflammatory cells. A Gram stain of the fluid did not demonstrate any pus cells or bacteria. Routine aerobic and anaerobic bacterial cultures were negative for bacterial growth. Mycobacterial smears and cultures were also negative. A direct mycology smear using calcofluor white was negative, but two colonies of a filamentous fungus were noted both on the routine sheep blood agar and chocolate agar culture plates after four days of incubation.


case presentation
A 54-year-old man from Guyana presented with a painful, nonery- thematous, subcutaneous nodule on his right patella at the site of a remote injury.The patient fell while climbing a coconut tree at 10 years of age, 44 years before presentation.The fall caused him to land on the stump of a 'black sage tree' injuring his right patella.Multiple small splinters from the stump penetrated his skin over and around his patella, which were removed shortly after the initial injury.The patient reported a significant amount of purulent discharge that eventually subsided.He was never treated with antibiotics.For approximately the next 40 years, the patient reported a history of knee swelling that dramatically increased in recent years.He reported no recent trauma.He experienced no fever, chills, sweats or recent weight loss.The patient was a nonsmoker, did not drink alcohol and had no history of injection drug use.
On examination, he was afebrile and looked well.There was no lymphadenopathy.There was a 4 cm × 4 cm nonerythematous, indurated nodule on the anterior aspect of the right patella.There was no joint effusion; however, there was a prepatellar bursitis.The lesion was not adherent to the patella and moved freely.Complete blood count, glucose level, renal function, hepatic transaminases and serum protein electrophoresis were all normal.He was HIV seronegative.A radiograph of the right knee did not demonstrate any foreign body or bone destruction.The prepatellar fluid was aspirated, producing thick fluid, tan-red in colour.Cytological analysis of the fluid showed histiocytes with inflammatory cells.
A Gram stain of the fluid did not demonstrate any pus cells or bacteria.Routine aerobic and anaerobic bacterial cultures were negative for bacterial growth.Mycobacterial smears and cultures were also negative.
A direct mycology smear using calcofluor white was negative, but two colonies of a filamentous fungus were noted both on the routine sheep blood agar and chocolate agar culture plates after four days of incubation.

Diagnosis
A second review of the mycology cultures after 17 days of incubation revealed a filamentous fungus.The fungus was identified as Pleurostomophora richardsiae based on gross and microscopic morphology (Figure 1).Its identification was confirmed with DNA sequencing.
The patient declined antifungal medications and surgical removal.He was subsequently lost to follow-up but then presented again one year later.On re-examination, the lesion remained unchanged.Fluid was aspirated and culture again produced P richardsiae.Again he declined therapy, and in follow-up surveillance, stated "I've lived with it this long, why do anything now?"

Discussion
P richardsiae is a rare dematiaceous (dark-walled) fungus that was previously known as Phialophora richardsiae but has been recently renamed (1).It was first isolated from a patient with a phaeomycotic cyst in 1968 (2).It is found in soil, decaying wood and vegetation.Although rare, infection has been reported worldwide but is believed to be more common in tropical climates (2,3).Similar to other dematiaceous fungi, disease can follow traumatic inoculation.
In general, dematiaceous fungi are associated with three disease states: phaeohyphomycosis, eumycotic mycetoma and chromoblastomycosis, which differ in their clinical presentation and histopathology.All three diseases are usually a result of traumatic introduction of the fungi into the skin and subcutaneous tissue.Host immunity and the specific fungal species both play a role in determining the clinical presentation.As in our patient, P richardsiae usually presents as phaeohyphomycosis, with skin and subcutaneous encapsulated cystic granulomas with central suppuration.Multiple abscesses may occur early in infection and disseminated disease primarily occurs in immunocompromised hosts.In addition to P richardsiae, subcutaneous phaeohyphomycosis may be due to a wide variety of other dematiaceous fungi such as Phaeoacremonium parasiticum, Exophiala jeanselmei and Wangiella dermatitidis (1,3).Therefore, it is important for clinicians to recognize the necessity of ordering mycology smears and cultures in persons who present with chronic cystic subcutaneous abscesses.In chromoblastomycosis, patients typically present with chronic localized skin and subcutaneous verrucoid, ulcerated or crusted lesions (1,4,5).Pseudoepitheliomatous hyperplasia with hyperkeratosis and parakeratosis and sclerotic bodies are seen on histopathology (1,5).One case of P richardisae presenting in this way was recently reported (6).Eumycotic mycetomas are midway in the spectrum of disease between phaeohyphomycosis and chromoblastomycosis.In eumycotic mycetoma, patients typically present with multiple draining sinus tracts and abscesses with granules containing septate hyphae seen on histopathology.The skin and subcutaneous tissues, primarily involving

CliniCAl Vignette
©2012 Pulsus Group Inc.All rights reserved  the lower leg and foot, are involved, but long-standing infections may extend to muscle, fascia and bone (3,4).
To our knowledge, this is the first documented case of P richardsiae to present after such a long period from initial inoculation (44 years).Because his initial trauma and likely inoculation occurred in 1964, four years before the organism was first described (1), this likely represents both the first and most recently recorded human case.The persistence of the organism in two aspirates one year apart confirms the chronicity of the infection.1).Only cases identified to the species level according to culture were included.Given the preponderance of cases in the tropics and subtropics, limiting the search to the English language could have excluded other reports.
The mean age of affected individuals was 49.3 years (range 15 to 80 years) with a male:female ratio of 3:1, possibly reflecting increased occupational and recreational exposure to wood chips and soil in men.Four of 12 (33%) cases that specified the patient's origin were inoculated and had presented in the developing world.Eight of 12 cases (67%), however, presented in the developed world.This disparity likely reflects a combination of the organism's long latency period and lack of diagnostic laboratory facilities in the developing world.
The most common manifestation of P richardsiae infection is a subcutaneous phaeohyphomycosis, with a well-circumscribed subcutaneous cyst filled with pus or serous material (17 of 22 cases).Histology usually consists of a pus-or serous-filled central cavity, surrounded by a fibrous wall with the appearance of a typical foreign body granuloma.In these 17 cases, infection remained localized, and regional adenopathy was not observed.Two patients with positive blood cultures developed disseminated, severe infection with this organism (7,8).One of these disseminated cases was in an HIV-positive, injection drug user (7) and the second case involved prosthetic valve endocarditis (8).Two cases involved endopthalmitis (8,9).Two cases of osteomyelitis occurred, one from hematogenous dissemination and one via local extension.A very indolent and prolonged course was documented in two previous cases that had 12-year (10) and 30-year (11) lag periods between injury and presentation, respectively.This suggests that this organism should be suspected in chronic, pus-filled, subcutaneous cysts with a history of localized trauma with soil or wood contamination, irrespective of how remote the trauma.The lack of history of trauma in some cases in the literature may be due to a long lag period between the time of injury and presentation with the lesion and, thus, a lack of recognition of the importance of the remote exposure.Therefore, it is important for clinicians to recognize the necessity of ordering mycology smears and cultures in persons who present with chronic, cystic, subcutaneous abscesses.
Pleurostomophora have been reported to have in vitro susceptibility to systemic antifungal agents such as amphotericin B, itraconazole, terbinafine, voriconazole and posaconazole (4,5,(7)(8)(9)(10).However, it was previously believed that dematiaceous fungi such as Pleurostomophora do not respond well to systemic antifungal therapy alone, making surgical excision the treatment of choice (12,13).Our literature review demonstrates that of the 17 cases of P richardsiae presenting as localized subcutaneous phaeohyphomycosis, the 10 treated with excision alone had successful outcomes.Of the three cases that were treated with both antimycotic agents and surgery, the only failure was in a highly immunocompromised patient (10).Three of four patients treated with antifungal agents alone had successful outcomes (7,11,12).The one case that failed antifungal therapy was treated with oral griseofulvin and topical naftifine and required subsequent excision; therefore, it is possible that antimycotic agents are more effective than previously believed.In cases with hematogenous dissemination, antimycotic agents remain central to therapy, although the small number of cases makes it difficult to clarify the clinical efficacy of different antifungal regimens.

Figure 1 )
Figure 1) A lactophenol aniline blue stain of Pleurostomophora richardsiae on potato dextrose agar incubated for 10 days.Prominent solitary phialides (arrows) with flared tips producing oval to round conidia were noted, typical of P richardsiae (original magnification ×400)

Table 1 Case reports of Pleurostomophora richardsiae -COnTinued author (reference), year General condition of patient (country, if specified) History and symptoms* Treatment Outcome
An Ovid MEDlINE and PubMed search revealed 22 other human cases of infection with P richardsiae in the world literature since 1968 (Table *All cases isolated P richardsiae.ESRD End-stage renal disease; RAPD Relative afferent pupillary defect