Carbohydrate-deficient glycoprotein syndrome (CDGS) is a congenital disorder characterized by neurological and developmental defects. We have examined the expressions of the small proteoglycans decorin and biglycan in cultured skin fibroblasts from a patient with CDGS Type-I. Northern blotting analysis identified a marked reduction in decorin mRNA and an increase in biglycan mRNA levels. The decorin protein in the culture medium was decreased. Responses to interleukin-1 β (IL-1 β) and transforming growth factor-β 1 (TGF-β 1) were apparently abnormal; decorin was only slightly up-regulated by IL-1 β, while biglycan was markedly down-regulated by IL-1 β and significantly up-regulated by TGF-β 1. The constitutional and developmental abnormalities characteristic of CDGS may be associated with such derangements in the expression of proteoglycan genes.