The case of an infant admitted for evaluation of severe emaciation with intermittent ocular anomalies including strabismus and nystagmus is reported. This case demonstrates the value of magnetic resonance imaging and transfontanellar ultrasonography for the diagnosis of diencephalic syndrome of infancy. The prognosis of this condition is usually grim, in particular because of the severe emaciation which is disproportionate with the tumour spread. Pathophysiologic hypotheses put forward to explain this cachexia are reviewed. Although cytokines such as TNF alpha are currently incriminated in the pathophysiology of cachexia induced by a number of conditions, they have not yet been studied in diencephalic syndrome of infancy. TNF alpha is a potent lipolytic agent. Excessive production of TNF alpha may be involved in the genesis of the emaciation characteristic of diencephalic syndrome. Inappropriate production of TNF alpha may respond to the administration of specific anti-TNF monoclonal antibodies. This approach may be considered as a means for treating emaciation in patients with diencephalic syndrome of infancy.