Varied clinical presentations of seven patients with mutations in CYP11A1 encoding the cholesterol side-chain cleavage enzyme, P450scc.

CONTEXT

The cholesterol side-chain cleavage enzyme P450scc, encoded by CYP11A1, converts cholesterol to pregnenolone to initiate steroidogenesis. P450scc deficiency can disrupt adrenal and gonadal steroidogenesis, resembling congenital lipoid adrenal hyperplasia clinically and hormonally; only 12 such patients have been reported previously.

OBJECTIVE

We sought to expand clinical and genetic experience with P450scc deficiency.

PATIENTS AND METHODS

We sequenced candidate genes in 7 children with adrenal insufficiency who lacked disordered sexual development. P450scc missense mutations were recreated in the F2 vector, which expresses the fusion protein P450scc-Ferredoxin Reductase-Ferredoxin. COS-1 cells were transfected, production of pregnenolone was assayed, and apparent kinetic parameters were calculated. Previously described P450scc mutants were assayed in parallel.

RESULTS

Four of five Bedouin children in one kindred were compound heterozygotes for mutations c.694C>T (Arg232Stop) and c.644T>C (Phe215Ser). Single-nucleotide polymorphism analysis confirmed segregation of these mutations. The fifth kindred member and another Bedouin patient presented in infancy and were homozygous for Arg232Stop. A patient from Fiji presenting in infancy was homozygous for c.358T>C (Arg120Stop). All mutations are novel. As assayed in the F2 fusion protein, P450scc Phe215Ser retained 2.5% of wild-type activity; previously described mutants Leu141Trp and Ala269Val had 2.6% and 12% of wild-type activity, respectively, and Val415Glu and c.835delA lacked detectable activity.

CONCLUSIONS

Although P450scc is required to produce placental progesterone required to maintain pregnancy, severe mutations in P450scc are compatible with term gestation; milder P450scc mutations may present later without disordered sexual development. Enlarged adrenals usually distinguish steroidogenic acute regulatory protein deficiency from P450scc deficiency, but only DNA sequencing is definitive.