We report clinicopathological features of a 23-year-old woman with
Down syndrome (DS) presenting with subacute
myelopathy treated with
chemotherapy, including intravenous and intrathecal administration of
methotrexate (MTX), and with allogenic
bone-marrow transplantation for B
lymphoblastic leukemia. Autopsy revealed severe demyelinating vacuolar
myelopathy in the posterior and lateral columns of the spinal cord, associated with macrophage infiltration, marked axonal loss and some swollen axons. Pathological changes of posterior and lateral columns were observed from the medulla oblongata to lumbar cord. Proximal anterior and posterior roots were preserved. Cerebral white matter was relatively well preserved. There were no vascular lesions or meningeal dissemination of
leukemia. Longitudinal extension of cord lesions was extensive, unlike typical cases of
subacute combined degeneration (SACD), but distribution of lesions and histological findings were similar to that of SACD. DS patients show heightened sensitivity to MTX because of their genetic background. Risk factors for toxic
myelopathy of DS are discussed, including delayed clearance of MTX despite normal renal function, alterations in MTX polyglutamation and enhanced
folic acid depletion due to gene dosage effects of chromosome 21. Alteration of
folate metabolism and/or
vitamin B12 levels through intravenous or intrathecal administration of MTX might exist, although
vitamin B12 and other essential nutrients were managed using
intravenous hyperalimentation. To the best of our knowledge, this is the first report of an autopsy case that shows
myelopathy mimicking SACD in a DS patient accompanied by B
lymphoblastic leukemia. The case suggests a pathophysiological mechanism of MTX-related
myelopathy in DS patients with B
lymphoblastic leukemia mimicking SACD.