Rhinocerebral mucormycosis is a rare, aggressive, and life-threatening fungal infection , occurring most often in diabetes patients suffering from ketoacidosis . At present, owing to the nonspecific early-stage symptoms of this disease, it is difficult to diagnose until it is relatively advanced.
Ocular manifestations are often the first presenting symptoms in patients suffering from rhinocerebral mucormycosis. These symptoms can include prominent eyeballs, swelling and redness around the eyes, impaired eye movement, decreased vision, and potentially blindness. Nasal black eschar formation is one of the most important clinical findings associated with rhinocerebral mucormycosis . CT or magnetic resonance imaging (MRI) examinations of the skull generally reveal the thickening of the sinus mucosa, sinusitis, bone destruction, and cavernous sinus thrombosis. These findings may be accompanied by facial swelling and numbness, local facial skin ulceration, local black necrotic eschar formation, and black eschar or ulcers on the epiphysis.
There are several approaches that can be used to diagnose rhinocerebral mucormycosis. Fungal culture is highly specific, but the sensitivity of this approach is just 25%, limiting its clinical applicability . Pathological assessment of biopsy samples can achieve a more definitive diagnosis, as affected patients generally exhibit large areas of coagulative necrotic tissue, fungal granuloma, fungal vasculitis, thrombosis, and bone destruction [5, 6]. Typical granulomatous tissues from affected patients generally contain hyphae and neutrophils surrounded by epithelioid cells, multinucleated giant cells, varying numbers of plasma cells, lymphocytes, and eosinophils. Perivascular and blood vessel invasion by fungal hyphae results in arterial thrombosis and subsequent necrosis. Hyphae are generally broad and irregularly shaped, with branches primarily forming at right angles . Hematoxylin and eosin staining of these hyphae largely fails to differentiate them from background tissues, and high magnification is often necessary to clearly resolve these fungal structures. PAS and Gomori methenamine silver (GMS) staining result in the purple-red and brown-black coloration to these hyphae, respectively, making them easier to observe [4, 6]. Molecular biology approaches can also be used to diagnose this condition, although it remains challenging to leverage a broad-spectrum for the diagnosis of mucormycosis in clinical settings .
From a differential diagnosis perspective, rhinocerebral mucormycosis may be confused with other forms of fungal sinusitis. Identification is mainly based on the morphological characteristics of fungal hyphae. Mucor mycelia are relatively thick (6–25 μm in diameter) and disordered, with thick walls, asymmetry, little separation, partial swelling and twisting, and relatively few branches that are primarily at right angles [5, 6]. In contrast, Candida mycelia are thin (2 - 4 μm in diameter) and can be bead-like , while Aspergillus mycelia are of medium thickness (5–10 μm in diameter), uniform in thickness, often exhibit directional growth, are frequently separated, and generally exhibit many branches that are most often formed at acute angles .
Treatment options for rhinocerebral mucormycosis include the active treatment of primary disease, correction of underlying acidosis, and the early administration of agents including amphotericin B liposomes, together with the thorough debridement of local necrotic tissue . Surgical and antifungal treatments generally form the cornerstones of treatment , and delays in initiating amphotericin B treatment for more than 6 days is associated with a doubling of mortality at 12 weeks.
In summary, we described a case of rhinocerebral mucormycosis secondary to severe acute pancreatitis in a patient suffering from diabetic ketoacidosis, with the optimal treatment window for this condition having been missed. This report suggests that a definitive mucormycosis diagnosis can be made based upon tissue biopsy that reveals the presence of characteristic hyphae. Early diagnosis and treatment are essential in order to improve patient prognosis.