[A case of rapidly progressive HTLV-I-associated myelopathy (HAM)]

We report a 65-year-old woman with HAM who showed rapid progression of the clinical symptoms. The initial symptom was lumbago and she became unable to walk within 4 months after the onset of the lumbago. When seen on admission, she had flaccid paraplegia and areflexia was seen in the lower extremities with positive Babinski and Chaddock reflexes. She had numbness below the level of the navel, vibratory sensation was decreased in both lower limbs, and there was a hyperesthesic zone at the tenth thoracic vertebral level. She had a difficulty in urination and defecation. Laboratory examination revealed elevated anti-HTLV-I antibody titers both in serum (4,096x by PA method) and in cerebrospinal fluid (CSF) (4,096x). The levels of IgG and neopterin in CSF were also increased to 16.6 mg/dl (normal: < 5 mg/dl) and 360.3 pmol/ml (normal: < 30 pmol/ml), respectively. HTLV-I messenger RNA positive cells were detected in 0.1% to 0.01% of cells in CSF by in situ hybridization using an oligonucleotide probe labelled with alkaline phosphatase. Spinal cord MRI detected neither spinal cord compression nor vascular diseases. She was treated with 1,000 mg methylprednisolone for 3 days intravenously, followed by 60 mg oral prednisolone therapy. In several days after receiving the treatments, her muscle tonus became spastic and deep tendon reflexes in the legs became brisk. The hyperesthesia at the tenth thoracic vertebral level and numbness below the level of the navel were also gradually improved. Subsequently, her clinical features were consistant with those of the typical HAM. Therefore, the patient was diagnosed as rapidly progressive HAM. The initial phase of rapidly progressive HAM patients had been described only from clinical history. These patients had common characteristic clinical features, such as older age at onset, relatively severe motor dysfunction, high titers of anti-HTLV-I antibody in CSF, and increased levels of neopterin and IgG in CSF, when compared with those of other HAM patients. The clinical course and laboratory findings in the present patient were compatible with those in the previous cases reported as rapidly progressive HAM. This patient showed flaccid paraplegia and areflexia which have rarely been seen in HAM patients. However, these symptoms were changed to spastic and hyperactive after prednisolone therapy. We speculate that inflammation in the spinal cord in this patient was severe enough to spread to the dorsal root, and disturbed the afferent pathway from the peripheral to the central nervous system. This inflammatory reaction might be suppressed by prednisolone to facilitate the recovery of the afferent pathway, which led to the typical clinical symptoms of HAM.