Compensatory growth after HLA-typing revelation of incorrect diagnosis of 21-hydroxylase deficiency.

A 9 1/2 year old boy had been treated for complete 21-hydroxylase deficiency from infancy. That diagnosis was excluded by HLA-typing of family members who wished to know their carrier status. Withdrawal of replacement therapy was very well tolerated. The patient showed distinct compensatory growth and for the first time was free of crises of adrenal insufficiency. This instance demonstrates an unexpected application of HLA-typing. It also shows that an amount of hydrocortisone too small to give any clinical evidence of overdose can impede growth. Furthermore, it provides reassurance that adrenocortical function can recover completely after many years of treatment with exogenous steroids.