PMC10146069_01
The cutaneous manifestation. (A) The maculopapular rash in dark purple appeared on the lower extremities; (B) The lesion in the pretibial skin rapidly progressed into 1-centimeter-sized ulcer.
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The maculopapular rash in dark purple appeared on the lower extremities (Figure 1A). The lesion in the pretibial skin rapidly progressed into a 1-centimeter-sized ulcer (Figure 1B).
99mTc-MDP bone scintigraphy showed an abnormal nuclide concentration in left clavicle region accompanied by left clavicle deformation.
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Rheumatoid factor, anti-streptolysin O, anti-cyclic citrullinated peptide antibody, human leukocyte antigen B27, antinuclear antibody, and parathyroid hormone were all negative. 99mTc-MDP bone scintigraphy showed an abnormal nuclide concentration in the left clavicle region accompanied by left clavicle deformation (Figure 2). 
HE staining: (A and B) Granulosa cell hyperplasia of epidermal small focus, and vascular cluster wall, nucleate dust and red blood cell spillover, which conform to the morphological manifestation of vasculitis. (C and D) Direct immunofluorescence showed deposition of IgA and C3 in the vessel walls of the lesion biopsy.
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Histopathological examination of a biopsy specimen from a lesion on the right anterior tibial skin showed that granulosa cell hyperplasia of epidermal small focus, and vascular cluster hyperplasia visible in the superficial layer of the dermis, with fibrin-like degeneration of vascular wall, nucleate dust and red blood cell spillover, which conform to the morphological manifestation of vasculitis (Figure 3A and B). Direct immunofluorescence showed deposition of IgA and C3 in the vessel walls (Figure 3C and D). 
After the treatment of methylprednisolone and tofacitinib, the ulcer was healed and other lesions were subsided.
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Skin ulcer began to heal and the rest of the skin lesions gradually scabbed and subsided 4 days later (Figure 4). 