A Case of a Preterm Infant with 21-Hydroxylase Deficiency: Implications of the Biochemical Diagnosis with Urinary Pregnanetriolone by Gas Chromatography/Mass Spectrometry in Selected Ion Monitoring (GCMS-SIM)

The biochemical diagnosis of 21-hydroxylase deficiency (21-OHD) is difficult in preterm infants. To date, no marker for the biochemical diagnosis of 21-OHD has been found. Seventeen α-hydroxyprogesterone (17-OHP), is not useful because of interference by delta 5 steroids from the fetal adrenal cortex. A 5-d-old female infant, born at 31 wk of gestation, was suspected of having 21-OHD based on physical findings (mild clitoromegaly, pigmentation of the tongue and gingiva) as well as laboratory data (17-OHP >93.5 ng/ml by ELISA 7 prime extractive method in filter paper-dried blood spot and 718.3 ng/ml by RIA after high performance liquid chromatography extraction in serum; plasma ACTH 690 pg/ml; and serum testosterone 3,169 ng/dl). We examined her urinary steroid profiles by gas chromatography/mass spectrometry in selected ion monitoring (GCMS-SIM) at 8 d of age. The pregnanetriolone (Ptl) level was noticeably high (0.80 mg/g creatinine), which was strongly suggestive of 21-OHD. Gene analysis of CYP21A2 showed compound heterozygosity, one allele having a cluster mutation in exon 6 and the other having a large deletion including CYP21A2, confirming the diagnosis of 21-OHD. This case suggested that, in preterm infants, urinary Ptl by GCMS-SIM can be useful for the biochemical diagnosis of 21-OHD.