Lack of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase in fibroblasts from a child with urinary excretion of 3 beta-hydroxy-delta 5-bile acids. A new inborn error of metabolism.
 Cultured fibroblasts were shown to be capable of catalyzing the conversion of 7 alpha-hydroxy-cholesterol to 7 alpha-hydroxy-4-cholesten-3-one, an important reaction in bile acid synthesis.
 The apparent Km was approximately 7 mumol/liter and Vmax varied between 3 and 9 nmol/mg protein per h under the assay conditions used.
 The assay was used to investigate fibroblasts from a patient who presented with a familial giant cell hepatitis and who was found to excrete the monosulfates of 3 beta, 7 alpha-dihydroxy-5-cholenoic acid and 3 beta, 7 alpha, 12 alpha-trihydroxy-5-cholenoic acid in urine (Clayton, P.
 T., J.
 V.
 Leonard, A.
 M.
 Lawson, K.
 D.
 R.
 Setchell, S.
 Andersson, B.
 Egestad, and J.
 Sjovall.
 1987.
 J.
 Clin.
 Invest.
 79:1031-1038).
 In addition 7 alpha-hydroxy-cholesterol was found to accumulate in the circulation.
 Cultured fibroblasts from this boy were completely devoid of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase activity.
 Fibroblasts from his parents had reduced activity, compatible with a heterozygous genotype.
 The results provide strong evidence for the suggestion that this patient's liver disease was caused by a primary defect in the 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase involved in bile acid biosynthesis.
