Longitudinal extensive transverse myelitis with an abnormal uFLC ratio in a pediatric patient: Case report and literature review

RATIONALE: The serum and urine-free light chain (sFLC/uFLC) ratios of kappa (κ) to lambda (λ) serve as biomarkers for plasma cell disorders, especially multiple myeloma. However, to our best knowledge, the ratios have not been appropriately assessed for acute transverse myelitis (ATM). PATIENT CONCERNS: We present a 12-year-old boy who had sudden onset low back pain following paralysis of his 4 extremities and disturbance consciousness. Magnetic resonance imaging (MRI) of the brain and spine indicated diffuse hyperintensity in T2-weighted images from the cervical spinal cord to the conus medullaris. An abnormal serum M-peak and uFLC ratio were detected in acute stage. DIAGNOSES: Based on the image findings, laboratory findings, and physical examination results, the diagnosis of acute transverse myelitis was established. INTERVENTIONS AND OUTCOMES: With the treatment of pulse therapy and 5 courses of plasmapheresis, the patient had improvement in expanded disability status scale (EDSS) score from 9 to 5. Besides, the κ/λ ratio was also returned within the normal range. LESSON: The case presented an unusual phenomenon of transient abnormal κ/λ ratio combined with an M-peak in the acute course of longitudinally extensive transverse myelitis (LETM), which revealed FLC ratio recovering accompany with the improvement of disease. Further studies are required to identify the association between ATM and monoclonal gammopathy of undetermined significance (MGUS).