GPA = granulomatosis with polyangiitis, LCH = Langerhans cell histiocytosis, SLE = systemic lupus erythematosus.

Master JM was started on oral Fluconazole and Co-amoxiclav, but the lesion grew aggressively and started involving his right orbit. He also developed significant submandibular and cervical lymphadenopathy. He was subsequently referred to an oncologist for further management. Chemotherapy treatment for suspected Langerhans Cell Histiocytosis (although immunophenotyping remained inconclusive) was initiated by the oncologist, but without clinical improvement. At the time of his referral, he had complete destruction of the right orbit with loss of vision in his right eye (Figures 1-3 show the progression of the lesion).

Figures 1-3: The pictures illustrate the progression of the lesion under the right eye (from left to right) (Written permission given by the parents)

The following laboratory tests were performed

Clinical features – important differentiating principles

Due to the histological evidence of a “vaguely granulomatous inflammatory process”, the initial diagnosis of Langerhans cell histiocytosis was made. Langerhans cell histiocytosis (LCH) is a rare clonal disease of the monocyte-macrophage system characterized by uncontrolled proliferation and accumulation of CD1a⁺/CD207⁺ dendritic cells (DCs) as a result of continuous immune stimulation. Langerhans cell histiocytosis can occur at any age. However, peak occurrence occurs between 1 and 4 years of age.  The diagnosis of LCH is based on histological criteria established by the Histiocyte Society in 1987. To make a diagnosis, it is necessary to perform a histological examination with immunophenotyping. The most frequent presenting signs and symptoms of LCH include painful bone lesions and rash. Often non-specific symptoms become prominent, such as fever, poor appetite, weight loss, fatigue, irritability and changes in behaviour.  In the youngest children, the disease is often an multisystem disease with fever and symptoms of failure in various organs. In a Japanese study, the patients with skin lesions were younger than those with bone lesions. In a previous French study, 77% of the patients with the skin lesion were less than 1 year old. Sometimes there are superficial ulcerations of the lesions accompanied by oozing as the result of secondary processes leading to a bacterial superinfection. Ulcerative lesions behind the ears or involving the scalp, axillae, genitalia, or perianal region are often misdiagnosed as bacterial or fungal infections.

Key learning points to diagnosis and therapeutic approaches in this case study

1. Invasion granulomatous skin lesions have a broad differential diagnosis, and can be life threatening if not diagnosed and treated early. A careful history, including trauma and predisposing risk factors, should be taken in all patients presenting with a rapidly enlarging skin lesion.
2. Adequate biopsies, including fresh specimens for bacterial and fungal culture, is imperative to make the correct diagnosis. Histopathology is a very important diagnostic tool since it distinguishes the presence of the fungus as a pathogen in the specimen from a culture contaminant and is indispensable to define whether there is blood vessel invasion. Routine hematoxylin and eosin (H&E) stains may show only the cell wall with no structures inside, or occasionally, very degenerate hyphae. Stains that can help highlight the fungal wall include Grocott methenamine-silver (GMS) and periodic acid-Schiff PAS stains, although PAS gives a better visualization of the surrounding tissue compared to GMS. For a rapid presumptive diagnosis of mucormycosis direct microscopy of KOH wet mounts can be used. It can be applied to all materials sent to the clinical laboratory, preferably using fluorescent brighteners such as Blankophor and Calcofluor White together with KOH, which enhance the visualization of the characteristic fungal hyphae, in this case requiring a fluorescent microscope. Direct microscopy of fresh material is an inexpensive, yet invaluable method to rapidly give a presumptive diagnosis and to define clear surgical margins for invasive fungal infection intraoperatively, and it is strongly recommended, along with histopathology, by a panel of experts of the European Confederation of Medical Mycology in cooperation with the Mycoses Study Group Education and Research Consortium (ECMM/MSG ERC). These methods, however, are not able to identify a fungus to the genus or species level. Another method, immunohistochemistry using monoclonal antibodies against R. arrhizus (recently commercially available) can aid in the diagnosis when cultures are negative and has been proven useful for differentiating aspergillosis from mucormycosis (sensitivity 100%, specificity 100% for mucormycosis) and has gained a moderate recommendation of B IIu in the recent ECMM/MSG ERC guidelines. Culture of specimens is essential for the diagnosis of mucormycosis since it allows identification to the genus and species level, and eventually antifungal susceptibility testing. Most medically important Mucorales are thermotolerant and are able to grow rapidly at temperatures of 37 °C. They grow on virtually any carbohydrate substrate, colonies appearing usually within 24–48 h and identification is based on colonial and microscopic morphology and growth temperature. Matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) identification of cultured Mucorales is a promising method for those laboratories that are accordingly equipped, but the commercially available databases should be expanded further, and more validation data are needed. Until then, molecular identification remains the gold standard. (4)
3. Invasive fungal infections such as mucormycosis need urgent surgical debridement together with aggressive antifungal therapy. Mucormycosis-associated 90-day mortality remains high despite the advent of newer antifungals. First-line antifungals with good efficacy and safety remain an urgent unmet need. Owing to its broad-spectrum antifungal activity, traditionally amphotericin B formulations have been the antifungal of choice for the treatment of mucormycosis. However, with the advent of newer triazoles, specifically posaconazole and isavuconazole, clinicians now have access to a wider range of therapeutic options. Intravenous lipid-based Ampho B does not confer a survival advantage over intravenous C-AmB but was associated with fewer adverse effects. Initial combination antifungal therapy is not associated with reduced mortality compared with initial AmB monotherapy, but requires further investigation. Surgery is fundamental to improving survival and must be accessible to all patients.(5)