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ObjectivePlasma assay for very long-chain fatty acids has made it possible to perform large-scale screening of at-risk individuals to identify asymptomatic patients with X-linked adrenoleukodystrophy (X-ALD). We evaluated the burden of undiagnosed adrenal insufficiency in 49 such patients (age, 4.5 +/- 3.5 years).Study designSerum adrenocorticotropic hormone (ACTH) and standard-dose ACTH stimulation test were performed at the baseline and followed prospectively until initiation of adrenal replacement therapy (follow-up, 2 +/- 1.7 years).ResultsAt baseline, 39 (80%) patients had impaired adrenal function, serum ACTH levels were elevated in 34 (69%) patients, and ACTH stimulation test was abnormal in 21(43%) patients. There was a moderate association between Serum ACTH and age at baseline, (r=0.32, P=.05). By the end of follow-up, 86% of patients had borderline or overt adrenal insufficiency (age of onset, 4.8 +/- 3.7 years).ConclusionsWe detected a high prevalence of unrecognized adrenocortical insufficiency in asymptomatic boys with X-ALD. It is known to be a frequent cause of morbidity and can be prevented by careful monitoring, early identification of impaired adrenal reserve, and timely initiation of therapy. It manifests early and before onset of neurologic symptoms, suggesting X-ALD as a candidate disorder for neonatal screening.

X-linked adrenoleukodystrophy (X-ALD) has variants with widely different outcomes, hampering clinical counseling and evaluation of therapies.