Cavity in pulmonary mucormycosis: Is it rare?

Sir,

We read with interest the article by Saini et al. ¹ The authors describe a successfully managed case of pulmonary mucormycosis (PM) in an individual with previously undiagnosed diabetes mellitus. ¹ We do not concur with the authors’ comment that cavity is a rare presentation of PM. ¹ The imaging findings in PM are influenced by several factors, including the risk factor (neutropenia versus other causes), the timing of imaging and the treatment response. The occurrence of a cavity in PM on imaging is as high as 48% in various studies.^2,3

Several radiologic findings have been reported in PM, including lobar consolidation, nodules, mass-like consolidation, halo sign, reversed halo sign (RHS), central low attenuation areas, cavities, cavities with intracavitary content and others. While nodules, halo sign and consolidation are early signs of PM, central necrosis, cavitation and crescent sign occur later. ⁴ The RHS, a widely recognised indicator of invasive PM in immunosuppressed individuals, is neither sensitive nor specific for PM. ⁵ One explanation for the lack of sensitivity of various radiologic appearances is the serial changes in these patients over time. ⁶ Case series from neutropenic patients with haematological malignancies suggest that PM may begin as areas of ground-glass opacities and progress to form nodules and consolidation. Some of these patients progressed to develop cavities, while a few others developed multifocal pneumonia. ⁷ In the series by Hammer et al., ⁷ a cavity was present in 10% (3/30) of the subjects in the initial computed tomography (CT) study, while, subsequently, eight more patients developed (37%) cavities. Unlike patients with haematological malignancy where early CT is performed, diabetics often remain unevaluated until late in the disease course. Non-specific symptoms, late presentation to medical facilities, lack of clinical suspicion, consideration of alternate diagnosis like tuberculosis, and delayed imaging explain the higher frequency of cavitation in diabetic individuals with PM. ³ Therefore, invasive mould infections, particularly PM, should be considered as an alternate possibility in diabetic subjects with cavities in addition to bacterial abscesses, tuberculosis and others.