A leukotriene C4-synthesis deficiency, a new inborn error of eicosanoid metabolism characterized by hypotonia, microcephaly, failure to thrive, and retarded development, is described in an infant who died aged 6 months after a rapidly progressive course at the University of Heidelberg, Germany. Concentrations of cysteinyl leukotriene LTC4 and its metabolites could not be detected in the CSF, plasma and urine, and could not be synthesised in stimulated monocytes or platelets, suggesting a deficiency of LTC4 synthase. Defective LTC4 synthesis was the presumed underlying basis for the fatal developmental syndrome. 
COMMENT. Cysteinyl leukotrienes are lipid mediators derived from arachidonic acid that have effects on vascular permeability, smooth-muscle tone, and mucus secretion. They cause bronchoconstriction, and antileukotriene drugs are now available for treatment of asthma. In addition to their role in allergic and inflammatory disorders, they are synthesized by brain tissue, concentrate in the hypothalamus, choroid plexus and CSF, and act as modulators of central nervous activity. They also affect neuroendocrine function. Leukotriene analysis of CSF should be performed in infants who have progressive neonatal neurologic deficits and consanguineous parents. Morris AAM and Rodger IW provide a helpful commentary on leukotienes and the brain.