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Letters to the Editor

Saksenaeae Subcutaneous Abscess in an Immunocompetent Child

Buzacott, Katie MBBS; Townell, Nicola MB ChB; Dettrick, Andrew FRCPA; Grimwood, Keith MD, FRACP

Author Information
The Pediatric Infectious Disease Journal: January 2016 - Volume 35 - Issue 1 - p 120
doi: 10.1097/INF.0000000000000942

To the Editors:

Molds, in the order Mucorales, are found worldwide in soil and decaying vegetation. They lead typically to disseminated infection in immunocompromised patients. In contrast, members of the family Saksenaeaceae can cause skin and soft-tissue infections in healthy individuals.1 We report a rare case of a subcutaneous abscess because of Saksenaea vasiformis in a previously healthy 4-year-old boy without a history of recent injury. He presented initially with calf cellulitis, which despite intravenous flucloxacillin, evolved into a subcutaneous abscess requiring multiple incision and drainage procedures (see Fig., Supplemental Digital Content 1, https://links.lww.com/INF/C291). He remained systemically well with a normal full blood count, C-reactive protein was 11 mg/L and erythrocyte sedimentation rate of 11 mm/h. Operative findings revealed caseous material and histology showed necrotic fat, suppurative inflammation and numerous pauciseptate hyphae with right-angled branching and angioinvasion (see Figs., Supplemental Digital Content 2 and 3, https://links.lww.com/INF/C292 and https://links.lww.com/INF/C293). Fungal culture demonstrated white woolly growth on day 10. Despite using nutrient deficient media, the fungus failed to sporulate and could not be identified morphologically; instead pan-fungal polymerase chain reaction and sequencing identified it as S. vasiformis. No growth was observed on bacterial and mycobacterial cultures. Immune function tests (including immunoglobulins, neutrophil oxidative burst, lymphocyte subsets and HIV serology) were normal. Once mucormycosis was confirmed, he began posaconazole 200 mg 4 times daily (10 mg/kg/dose, serum trough level range 1.5–2.0mg/L) and terbinafine 62.5 mg once daily, which he tolerated well during the 3-month treatment course. Since ceasing therapy, he has been in good health without recurrence of the abscess.

Most reported cases of S. vasiformis have involved immunocompetent adults, with few infections described in children. Of the 10 reported cases in children (including our own), 8 were male and only 2 had recognized risk factors (acute lymphoblastic leukemia and thalassemia, respectively).2,3 Five had localized soft-tissue infections, 2 had rhino-orbital infections and 3 developed disseminated disease. In six cases, the inoculation source was unknown. Children were treated with both surgical debridement and various combinations of antifungal drugs. Of the 3 recorded deaths, each could be attributed respectively to an underlying immunocompromised state,2 extensively contaminated wounds4 or diagnostic delay resulting in suboptimal therapy.5

A tissue biopsy, with characteristic histologic findings, is necessary to establish the diagnosis of cutaneous mucormycosis. Nevertheless, microbiologic-based methods are required to identify the causative fungal pathogen. Traditionally, species identification relied upon sporulation to reveal unique flask-shaped sporangia. However, as S. vasiformis regularly fails to sporulate on routine mycological media, it is likely that infection with this fungus has been underestimated. Newer molecular techniques, such as pan-fungal polymerase chain reaction and sequencing, allow species identification to be performed either from culture isolates or directly from fresh tissue, preferably before tissue is fixed in formalin.

Successful management relies upon surgical debridement and early initiation of antifungal therapy. Amphotericin B has traditionally been the treatment of choice for mucormycoses. However, terbinafine and posaconazole are promising treatment options and have the added advantages of oral formulations and good safety profiles. Both were more active than amphotericin B against S. vasiformis in vitro.1 Posaconazole was also superior to amphotericin B in treatment of disseminated S. vasiformis infection in an immunocompetent murine disease model.6 Despite case reports of successful treatment of S. vasiformis infections,7,8 posaconazole is not licensed in children aged <13 years. Limited published data in this age group indicate it is generally well tolerated, but requires drug monitoring as oral bioavailability is unpredictable.9

Although rare, S. vasiformis should be considered when skin and soft infections are not responding to otherwise appropriate therapy, especially if tissue necrosis is present.

Katie Buzacott, MBBS

Department of Microbiology

Pathology Queensland Central Laboratory

Nicola Townell, MB ChB

Department of Microbiology

Pathology Queensland Central Laboratory

Andrew Dettrick, FRCPA

Department of Anatomical Pathology,

Pathology Queensland

The Prince Charles Hospital

Keith Grimwood, MD, FRACP

Queensland Children’s Medical Research Institute

Children’s Health Queensland

Department of Infectious Disease

Royal Children’s Hospital

Brisbane, Australia

REFERENCES

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