Abstract
Sarcoidosis and tuberculoid leprosy (TL) are prototypes of granulomatous inflammation in dermatology, which embody one of the histopathology limitations in distinguishing some diseases. Recent advances in the use of nonlinear optical microscopy in skin have enabled techniques, such as second-harmonic generation (SHG), to become powerful tools to study the physical and biochemical properties of skin. We use SHG images to analyze the collagen network, to distinguish differences between sarcoidosis and TL granulomas. SHG images obtained from skin biopsies of 33 patients with TL and 24 with sarcoidosis retrospectively were analyzed using first-order statistics (FOS) and second-order statistics, such as gray-level co-occurrence matrix (GLCM). Among the four parameters evaluated (optical density, entropy, contrast, and second angular moment), only contrast demonstrated statistical significance, being higher in sarcoidosis (p = 0.02; 4908.31 versus 2822.17). The results may indicate insufficient differentiating power for most tested FOS and GLCM parameters in classifying sarcoidosis and TL granulomas, when used individually. But in combination with histopathology (H&E and complementary stains, such as silver and fast acid stains), SHG analysis, like contrast, can contribute to distinguishing between these diseases. This study can provide a way to evaluate collagen distribution in granulomatous diseases.
Highlights
Leprosy is an infectious and contagious chronic disease, caused by Mycobacterium leprae, an obligate intracellular bacillus that mainly affects skin, nerves, and mucous membranes
After second-harmonic generation (SHG) images acquisition, we concluded that a very scant signal could be detected inside the granulomas
Among the gray-level co-occurrence matrix (GLCM) parameters, entropy and second angular moment (SAM) values were similar, but contrast was significantly higher in sarcoidosis (p 1⁄4 0.02; 4908.31 versus 2822.17)
Summary
Leprosy is an infectious and contagious chronic disease, caused by Mycobacterium leprae, an obligate intracellular bacillus that mainly affects skin, nerves, and mucous membranes It can affect the eyes, noses, joints, lymph node, internal organs, and bone marrow, especially in multibacillary patients.[1,2] Currently worldwide, more than 200,000 new cases of leprosy are detected annually, with India, Brazil, and Indonesia accounting for ∼80% of all new cases.[3] Brazil occupies second place in the world in absolute number of cases. Polymerase chain reaction is limited in M. leprae DNA detection in the tuberculoid pole of leprosy,[7,8,9] and this type of mycobacterium cannot be cultivated in an artificial culture medium
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