PMC10443697_01
Images of the skin lesions on the scalp of the patient before (A), during (B), and after treatment (C) respectively. (A) A coin-shaped subcutaneous nodule was viewed on the forehead area, with a smooth surface and missing hairs on the scalp. (B) The red gelatinous material was removed by curettage during surgery. (C) Inconspicuous scars were left in the original skin lesions.
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However, when palpating, a subcutaneous swelling (1.5x2 cm) below the alopecia lesion was noticed that had no obvious boundary or fluctuation (Figure 1A). During the surgery, red gelatinous discharge in the subcutaneous lump was removed by curettage (Figure 1B). Benzalkonium chloride solution was applied topically to the affected area. By the end of the treatment, the lump was not palpable, and new hair grew except for the presence of an inconspicuous scar in the surgical area (Figure 1C).
The pictures show the results of Middle Brook 7H11 Agar culture. (A) Results of the direct culture of red gel-like substance during operation. Visible cheese-like opaque colonies with round, neat edges, smooth and different sizes. (B) The growth morphology of the isolated strain inoculated on Middle Brook 7H11 Agar for seven days.
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However, round milky white yeast-like colonies of varying sizes were found on M7H11 Agar (Figure 2). 
The phylogenetic tree of Mycobacterium abscessus (B21), isolated from the infected site in an adult female in China, was constructed by MEGA 7.0 software. We selected Nocardia seriolae ATCC 43993 as the outgroup.
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We constructed a phylogenetic tree (Figure 3) based on ITS and beta-tubulin sequences using the maximum-likelihood method in MEGA 7.0.
The specimen from the scalp lesion was stained with hematoxylin-eosin (HE) and was observed under the light microscope. (A) There was no change of epidermal, and mixed inflammatory cells infiltration in deep dermis and subcutaneous fat (original magnification 40x). (B) Perifollicular inflammatory cells infiltrate (original magnification 100x). (C and D) The infiltrating cells are mainly lymphocyte and plasma cells (original magnification 200x) (C) and (original magnification 400x) (D).
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These infiltrates consist mainly of abundant lymphocytes and plasma cells, along with a smaller number of epithelioid histiocytes and scarce neutrophils (Figure 4A-D).