Ankle clonus correlating with cyanide intake from cassava in rural children from Mozambique.
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Biomedical subjects
Publications and source records attributed to J Cliff.
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Thyroid function was studied in a rural population in Mozambique that had been affected by an epidemic of spastic paraparesis attributed to dietary cyanide exposure from cassava. Laboratory investigation on a sample of this population demonstrated very high levels of serum and urinary thiocyanate, indicating a heavy exposure to cyanide. The urinary excretion of iodine was within normal limits, indicating an adequate intake of iodine. The serum levels of FT4I were somewhat decreased and serum FT3I, T3/T4 ratio and TSH were somewhat raised. This hormone pattern suggests an adaptation to the antithyroid effect of thiocyanate, but not overt hypothyroidism. A follow-up study on school children was performed, and it also demonstrated high thiocyanate exposure, adequate intake of iodine, and absence of endemic goitre. The results show that if iodine supply is adequate, the thyroid gland is capable of adaptation to a heavy body burden of thiocyanate without development of overt hypothyroidism or goitre.
Urinary excretion of sulphur compounds was studied in children from a population in Mozambique that had been affected, during a drought, by an epidemic of spastic paraparesis attributed to cyanide exposure from cassava. The children had increased thiocyanate and decreased inorganic sulphate excretion, indicating high cyanide and low sulphur-containing amino-acid intake. Children from a neighbouring cassava-eating area, where no cases of spastic paraparesis had occurred, had lower thiocyanate excretion but higher inorganic sulphate excretion. These results support the hypothesis that the epidemic was due to the combined effects of high dietary cyanide exposure and sulphur deficiency.
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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.