Congenital adrenal hyperplasia due to 21-hydroxylase deficiency associated with bilateral keratoconus.

Purpose: To report a clinical association between congenital adrenal hyperplasia and keratoconus.
Design: Observational case report.
Methods: Two 25-year-old dizygotic female twins were retrospectively studied. Clinical history, hormonal serologic profile, complete ophthalmologic examination, and Holladay Diagnostic Summary variables were evaluated. In the course of a 15-month follow-up period, a progression of the corneal disease was observed.
Results: In both twins a diagnosis of nonclassical congenital adrenal hyperplasia, due to 21-hydroxylase deficiency, was established when they were 21 years old. In one subject, the computed corneal topographic analyses diagnosed an asymmetric keratoconus in both eyes. A progressive form of fruste central keratoconus was also documented in her sister.
Conclusions: Congenital adrenal hyperplasia may be associated with keratoconus. An abnormal steroidogenic pathway, affecting the normal development of the cornea, could induce stromal abnormalities that lead to corneal ectasia.