We hypothesize that the combination of a null allele (p.103_155del) with a partial loss-of-function allele [p.(E99K)] in STAR along with reduced function of P450scc due to the CYP11A1 variant results in the phenotype; in effect, that sub-optimal function of the STAR protein, with biallelic inheritance of the two variants, alongside haploinsufficiency of p450scc side chain cleavage (CYP11A1) can be enough to reduce steroidogenic output such that the patient has late onset glucocorticoid deficiency but preserved mineralocorticoid and gonadal steroid production. This evidence concerns the gene CYP11A1 and familial glucocorticoid deficiency.