The authors describe a female patient with a serious lactate acidosis, which became manifest at the age of seven months. The clinical picture was dominated by neurological and cardiological symptomatology of uncertain etiology. An urgent examination excluded an inherited developmental anomaly, poisoning or infectious diseases. Non-specific findings during specific biochemical examinations did not confirm suspected hereditary metabolic disorder. In view of the resistance of lactate acidosis to alkalization therapy and for a deteriorating clinical condition of the child the authors administered 25 mg of thiamin intramuscularly. After six hours the lactate concentration decreased to normal values and the clinical sings of the child gradually adjusted to normal condition. The mother of the patient admitted that instead of giving the child the recommended Nutrilon Soya, she gave the child a dry soya drink without thiamin purchased in a common grocery. A detailed analysis of the clinical course and laboratory findings confirmed that the little child suffered from a suckling form of beri-beri.

        Key words: lactate acidosis, thiamin, beri-beri, the suckling age