HTLV-1 and tropical spastic paraparesis. 1. Clinical features, pathology and epidemiology

Disability and determinants of gait performance in tropical spastic paraparesis/HTLV-I associated myelopathy (HAM/TSP)

STUDY DESIGN

Cross-sectional.

OBJECTIVES

The aim of this survey is to describe the disability profile in a group of tropical spastic paraparesis/HTLV-I-associated myelopathy patients, identifying the requirements for community ambulation.

SETTING

Tertiary care unit, Rio de Janeiro, Brazil.

METHODS

Seventy-two patients were assessed (49 female and 23 male), referred by tertiary care centers, when a clinical protocol was applied.

RESULTS

The sample had an average age of 40 years and an average of 137 months of duration of the disease. The most prevalent aspects of disability found were in gait and sphincter control areas. A total of 72% of the patients were community ambulators and 17% were restricted to wheel chair. Age, strength and low-back pain interfere in activities of daily living (P<0.05). A positive correlation was found between community ambulation and the knee extensors (r=0.80) and ankle plantar flexors (r=0.74). Strength, age, low-back pain, duration of disease, asymmetric onset of the symptoms and spasticity interfered in the ability to walk (P<0.05). A rehabilitation program was proposed focusing on modifiable factors that affect disability level.

CONCLUSION

It was possible to describe the profile of disability in this group of patients, identifying the requirements to the community ambulation.

Long-term follow-up of konzo patients

Nine patients with konzo, a symmetric spastic paraparesis of acute onset that occurs during agricultural crises in cassava-growing areas, were re-examined after 14 years. Konzo outbreaks are associated with eating insufficiently processed bitter cassava and a low intake of essential amino acids. Bitter cassava contains cyanogenic glycosides; processing breaks them down to acetone cyanohydrin and hydrogen cyanide. This long-term follow-up showed that the neurological signs in konzo patients remained constant. Four severely affected patients, however, showed functional improvement. This non-progression clearly distinguishes konzo from myelopathy associated with human T lymphotropic virus type I infection. One child, originally classified as a konzo case, showed signs of cretinism at follow-up.

The epidemiology of myelopathy associated with human T-lymphotropic virus 1

A progressive spastic myelopathy is one of the principal manifestations of the human T cell lymphotropic virus type 1. Recent research is reviewed on the geography and epidemiology of this specific form of tropical spastic paraparesis. First recognized in the Caribbean, Colombia and Japan, it is now also confirmed as a major neurological problem in areas of eastern Brazil, western equatorial Africa, Natal and Seychelles, with other scattered foci world-wide. Accurate surveys call for sophisticated techniques including polymerase chain reaction amplification. The only defined modes of spread are by breast feeding, sexual contact and blood cell infusion. The onset of neurological disease is associated with high antibody titres and a high rate of spontaneous T lymphocyte proliferation. Molecular analysis has revealed no nucleotide sequence variation in cases with or without myelopathy. In non-transfusion cases the clinical attack rate is low with a very long latent period, but there are unexplained regional differences and familial cases are an important exception. Current research is focused on possible local, ethnic, or genetic co-factors.

Human retroviruses

It was only in 1980 that the first human retrovirus, HTLV-1, was isolated. Since then, HTLV-2, HIV-1 and HIV-2 have been identified. All four viruses are transmitted with varying efficiency sexually, vertically from mother to infant, and through blood by transfusion or contamination. HTLV-1 is endemic in populations in south-west Japan, Taiwan, sub-Saharan Africa, the Caribbean, southern USA, central and south America, Australia, Papua New Guinea, Solomon Islands and western Asia. There is now epidemic spread amongst IVDUs in north and south America and southern Europe. HTLV-1 is the aetiological agent of adult T-cell leukaemia/lymphoma (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). Other associations which may be causative are with polymyositis, infective dermatitis, gastrointestinal malignant lymphoma and chronic lymphatic leukaemia. ATL appears to be due to malignant transformation of HTLV-1 infected cells, and TSP/HAM to chronic activation of these cells. The epidemiology of HTLV-2 is being separated only recently from HTLV-1 through the application of PCR. It has a low level of endemicity in populations of central Africa, and central and south America. It is being spread epidemically amongst IVDUs in north America and southern Europe. Its association with any pathology in man remains uncertain. HIV-1 is epidemic and spreading rapidly throughout the world. In areas where homosexual contact was the predominant mode of transmission, heterosexual spread is becoming increasingly important. The areas where heterosexual contact is the predominant mode of transmission include the worst affected populations in the world, for example sub-Saharan Africa and some of the Caribbean. There have been recent and explosive increases of HIV-1 seroprevalence in IVDUs and female prostitutes in Asia, especially Thailand and India. Of the diverse pathology following infection, only the haematological consequences are reviewed in detail: these include anaemia, leucopenia, thrombocytopenia, disorders of coagulation and lymphomas. HIV-2, compared to HIV-1, is less infectious and causes less immunosuppression with more slowly progressive disease. It is prevalent in west Africa, but is spreading, albeit slowly, far beyond.