HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP) with amyotrophic lateral sclerosis-like manifestations.

To clarify the existence of HAM/TSP presenting amyotrophic lateral sclerosis (ALS)-like manifestations, we assayed HTLV-I proviral load in peripheral blood mononuclear cells (PBMC) in 15 patients with anti-HTLV-I antibody in serum and ALS-like manifestations (upper motor neuron involvement in at least one region and lower motor neuron involvement in at least two limbs) by quantitative PCR, and compared the proviral load with that of 233 HAM/TSP patients and of 213 HTLV-I carriers. Five of 15 patients with ALS-like manifestations had proviral loads as high as those in the 233 patients with HAM/TSP. Anti-HTLV-I antibody in cerebrospinal fluid (CSF) was present in all of five patients. The proviral load in the remaining 10 patients was similar to that in HTLV-I carriers. Four of five patients with a high proviral load met the diagnostic criterion of HAM/TSP except for lower motor neuron involvement. These four patients showed high neopterin levels in CSF. On the basis of HTLV-I proviral load in PBMC and the clinical symptoms, our tentative conclusion is that these four patients are HAM/TSP presenting ALS-like manifestations.