Familial adrenocorticotropin unresponsiveness associated with alacrima and achalasia: biochemical and molecular studies in two siblings with clinical heterogeneity

Abstract

The syndrome of familial adrenocorticotropin (ACTH) unresponsiveness is a rare form of primary adrenal insufficiency, usually without mineralocorticoid deficiency. It is characterized by elevated plasma ACTH concentrations and undetectable plasma cortisol levels not responding to exogenous ACTH. Alacrima and achalasia have also been occasionally associated with adrenal insufficiency (triple A syndrome). Pathogenetic mutations have been identified in the ACTH receptor gene in families with isolated familial ACTH unresponsiveness. Whether the ACTH receptor represents the locus of the defect for the triple A syndrome is not known. Here we report two siblings with familial ACTH unresponsiveness who were discrepant for skin pigmentation and mineralocorticoid function. In addition, achalasia and alacrima were documented only in the older sibling. The boy, studied at the age of 2 years, was hyperpigmented, in contrast to his normally pigmented sister, studied at the age of 9 years; basal plasma alpha-melanocyte stimulating hormone immunureactivity levels were 79 and 38 pg/ml, respectively (normal < 40 pg/ml). Furosemide-induced diuresis resulted in normal rises of plasma renin activity in both patients; however, plasma aldosterone levels increased only in the boy and not in his sister. Screening for abnormalities of the ACTH receptor gene by single strand conformation polymorphism analysis revealed no abnormality. Direct sequencing of the entire coding area of the ACTH receptor gene was also normal.

Conclusion: The syndrome of familial ACTH unresponsiveness can vary clinically and biologically within the same family.(ABSTRACT TRUNCATED AT 250 WORDS)