PERIPHERAL CHEMORECEPTORS IN CONGENITAL CENTRAL HYPOVENTILATION SYNDROME

Congenital central hypoventilation syndrome (CCHS) is a rare disorder of unknown etiology, characterized by failure of the autonomic control of respiration. The primary defect is believed to involve central res piratory control; however, no specific lesion has been identified. We report two cases of CCHS (one female, 3 mo of age and one male 2 yr of age) in which there was detailed examination of the neural, muscular, and chemoreceptor components of respiratory control. Although no spec ific abnormalities were identified in the central nervous system (CNS) or muscles of respiration, striking changes were observed in arterial chemoreceptors, carotid bodies (CB), and airway chemoreceptors, neuro epithelial bodies (NEB). In both cases, CB were small (< 50% of contro l), with a marked decrease in the number of glomus cells identified by immunostaining for tyrosine hydroxylase and serotonin. Ultrastructura l analysis of glomus cells in Case 1 showed a marked decrease in the f requency of dense core vesicles (< 20% of control), the storage site o f amine and peptide neurotransmitters. Immuno-staining for $100 protei n, a marker of sustentacular or Type II cells, was increased up to two fold compared with controls. In the lung, the frequency and size of NE B immunostained for bombesin was increased twofold in both cases, sugg esting compensatory hyperplasia of airway chemoreceptors. Since intact peripheral chemoreceptors are essential for respiratory control, espe cially the response to hypoxia, abnormalities in CB and NEB may contri bute to the pathophysiology of CCHS and related conditions such as sud den infant death syndrome (SIDS).