PMC4158253_01
Axial FSE T2-weighted fat-suppressed image at presentation shows complex right gluteal subcutaneous collections with heterogeneous high T2-weighted signal intensity and low T1-weighted signal intensity (not shown). The tubular collections (white arrows) are reminiscent of branching primary and secondary sinus tracts and probably represent the chronic phase of these suppurative inflammatory tracts, extending to the deep right ischiorectal and ischioanal spaces. Bilateral dermal thickening and induration are seen. Bilateral enlarged inguinal lymph nodes are also demonstrated (*).
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fig1
MRI of the pelvis was performed, which showed extensive subcutaneous abscesses, sinus, and fistula tracts in the right gluteal region where communicating and noncommunicating rim-enhancing collections were seen after IV contrast, extending deep into the right ischioanal fossa (Figures 1 and 2) and caudally to the right thigh (Figure 3). Marked skin thickening and subcutaneous induration over the lower back and both posterior thighs were observed.
Coronal FSE T1-weighted fat-suppressed post-IV Magnevist 10 mls. Note: rim-enhancement of these collections post-IV contrast (white arrows), consistent with abscesses.
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fig2
MRI of the pelvis was performed, which showed extensive subcutaneous abscesses, sinus, and fistula tracts in the right gluteal region where communicating and noncommunicating rim-enhancing collections were seen after IV contrast, extending deep into the right ischioanal fossa (Figures 1 and 2) and caudally to the right thigh (Figure 3). Marked skin thickening and subcutaneous induration over the lower back and both posterior thighs were observed.
Coronal T1-weighted fat-suppressed image postcontrast shows inferior extension of the rim-enhancing abscess along the medial aspect of the right thigh (white arrows). Note: associated bilateral dermal induration best seen in the perineum with abnormal enhancement (*).
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fig3
MRI of the pelvis was performed, which showed extensive subcutaneous abscesses, sinus, and fistula tracts in the right gluteal region where communicating and noncommunicating rim-enhancing collections were seen after IV contrast, extending deep into the right ischioanal fossa (Figures 1 and 2) and caudally to the right thigh (Figure 3). Marked skin thickening and subcutaneous induration over the lower back and both posterior thighs were observed.
Axial T1-weighted fat-suppressed axial (a) and coronal (b) images postcontrast in an MRI pelvis done 3 years before presentation using fistula-in-ano protocol demonstrates an enhancing transphincteric fistula tract at 6 o'clock position (white arrows in both images) extending to the right ischioanal space (thick arrow) with cutaneous opening at the right gluteal region (star).
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fig4
Similar to prior presentations, the deep right ischioanal abscess is closely related to a chronic transphincteric perianal fistula, better shown on a previous MRI (performed with fistula-in-ano protocol with smaller FOV) done 2 years before the current admission (Figure 4).
Axial T1-weighted fat-suppressed image postcontrast shows a well-defined rim-enhancing collection (white arrows) at the anterior perisacral space compatible with abscess, as well as abnormal marrow enhancement (thick arrow) in the sacrum consistent with osteomyelitis.
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fig5
There is also extension of the abscess to the anterior perisacral region, with adjacent sacral bony erosions and abnormal marrow enhancement indicating osteomyelitis (Figure 5).
Tissue specimen of debrided right thigh shows skin surface lined by squamous cell carcinoma (open arrow).
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fig6
Tissue specimens that were sent for histology incidentally revealed well-differentiated squamous cell carcinoma that has arisen from the chronic sinus tracts at the right thigh (Figure 6).
PET-CT performed after surgical excision of the right squamous cell carcinoma in the right thigh with wide resection margins. Note: FDG-avid foci in the perianal spaces ((b), arrowheads) and a more superior abscess collection at the left posterior back ((c), thick arrow), extending to the sacral level ((a), white arrows).
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fig7
F-18 FDG was performed for staging, which showed no evidence of focal hypermetabolic lesion to suggest distant metastases. FDG-avid inflammation was however observed at the lesions of HS consistent with the subcutaneous inflammation (Figure 7).
Frontal radiograph of the right hand shows focal periarticular soft tissue swelling at the proximal interphalangeal joint of the 2nd digit (thick arrow), suspicious for dactylitis. A small juxta-articular erosion is also noted at the middle phalanx of the middle finger (white arrow), which may represent the arthropathic changes related to HS.
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fig8
Radiographs demonstrated periarticular soft tissue swelling at the 2nd proximal interphalangeal joint and a small juxta-articular erosion at the 3rd distal interphalangeal joint (Figure 8).