Angioinvasive fungal infection involving the spinal cord and paraspinal soft tissues: a black turbinate sign-like MRI pattern

Background Angioinvasive fungal infections (AIFIs), including mucormycosis and aspergillosis, are life-threatening complications in immunocompromised patients. The lungs, orbitofacial sinonasal region, and central nervous system are among the most commonly affected sites, whereas spinal cord involvement is rare. Diagnosis remains challenging because of the nonspecific clinical presentation and the limited of sensitivity of conventional microbiological methods (Antinori et al., n.d. ( Antinori et al., 2018 )). However, characteristic imaging findings in specific organs can facilitate diagnosis. The “black turbinate sign” on contrast-enhanced magnetic resonance imaging (MRI) of the paranasal sinuses is a well-recognised feature suggestive of mucormycosis (Safder et al., 2010a ( Safder et al., 2010 )). We report a rare case of AIFI presenting with rapidly progressive myelopathy and extensive paraspinal soft tissue involvement, in which early diagnosis was facilitated by recognition of a black turbinate sign-like MRI pattern in the lumbar region. Case report A 54-year-old woman with B-cell acute lymphoblastic leukaemia developed persistent neutropenic fever after reinduction chemotherapy. Despite broad-spectrum antimicrobial therapy, the patient developed abdominal and back pain, followed by rapidly progressive paraplegia. MRI revealed an oval hypo-enhancing lesion extending from the left diaphragm to the paraspinal muscles, resembling the black turbinate sign. Diffusion restriction at the lesion margins involved the lumbar spinal cord and left kidney, suggesting infarction. An AIFI, most likely mucormycosis, was suspected, and liposomal amphotericin B was initiated. Results Serum Aspergillus antigen, β-D-glucan, and blood cultures were negative. Histopathological examination of a paraspinal muscle biopsy specimen demonstrated intravascular fungal hyphae and tissue necrosis, confirming an AIFI. Following antifungal treatment, the patient's condition stabilised. Conclusion This case highlights a rare AIFI involving the spinal cord and paraspinal tissues. MRI played a critical role in early diagnosis by demonstrated infarction-like changes associated with AIFI. Recognition of black turbinate sign-like pattern outside the sinonasal region may facilitate earlier diagnosis and treatment of this life-threatening condition.