To evaluate the human T-cell lymphotropic virus type I (HTLV-I) proviral DNA load among asymptomatic HTLV-I-infected carriers and patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), real time PCR using TaqMan probes for the pol gene was performed in two million peripheral blood mononuclear cells (PBMC). The albumin gene was the internal genomic control and MT2 cells were used as positive control. The results are reported as copies/10,000 PBMC, and the detection limit was 10 copies. A total of 89 subjects (44 HAM/TSP and 45 healthy HTLV-I-infected carriers) followed up at the Institute of Infectious Diseases "Emilio Ribas" and in the Neurology Division of Hospital of Clínicas were studied. The asymptomatic HTLV-I-infected carriers had a median number of 271 copies (ranging from 5 to 4756 copies), whereas the HAM/TSP cases presented a median of 679 copies (5-5360 copies) in 10,000 PBMC. Thus, HAM/TSP patients presented a significantly higher HTLV-I proviral DNA load than healthy HTLV-I carriers (P = 0.005, one-way Mann-Whitney test). As observed in other persistent infections, proviral DNA load quantification may be an important tool for monotoring HTLV-I-infected subjects. However, long-term follow-up is necessary to validate this assay in the clinical setting.

In acquired ichthyosis related to HTLV-I-associated myelopathy, histopathology revealed orthokeratotic hyperkeratosis and a perivascular inflammatory infiltrate of mononuclear lymphocytes, with areas of parakeratosis and foci of epidermotropism in rare cases. The expression profiles of K1, K10 and involucrin were similar to those in normal skin. The diffuse coexpression of K16 with K1 and K10 throughout the analysed epidermis, as well as the occurrence of restricted areas of parakeratosis expressing K6, indicate the presence of keratinocyte activation with induction of the alternative keratinization pathway, probably dependent on the cytokines liberated by the mononuclear cells of the dermal inflammatory infiltrate infected with HTLV-I. The absence of acanthosis and of increased cellular kinetics, as shown by the low rate of Ki-67 antigen expression, allow the inference that the pattern of acquired ichthyosis related to HTLV-I-associated myelopathy may be retentional. The observation of foci of parakeratosis expressing K6 in three specimens suggests that, at least in certain areas and in some cases, interference with epidermal differentiation and maturation occurs.

We report epidemiologic and clinical features of human T cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis in a Brazilian cohort of 86 patients from a university hospital. Cerebrospinal fluid (CSF) abnormalities and magnetic resonance imaging (MRI) findings were correlated with neurologic signs and symptoms. The patients’ mean age at disease onset was 43.2 years and the female to male ratio 1.5:1. Risk factors for retroviral exposure included blood transfusions, sexual transmission and intravenous drug use. Neurologic manifestations consisted mostly of spastic paraparesis, of gradual and asymmetric onset, with increased deep-tendon reflexes. Disability was associated with disease duration. CSF findings included mild mononuclear pleocytosis and elevated protein levels. MRI showed hemispheric areas of high signal intensity in 32.7% and spinal cord atrophy in 5.6% of cases, particularly in patients with longer duration of disease. A high frequency of past blood transfusion (32.6%) suggests that blood-borne infection was an important means of HTLV infection before implementation of screening of blood donors in Brazil.