A case of adrenoleukodystrophy in a 9-year old boy revealed by a predominant frontal syndrome is reported. Brain MRI showed an unusual pseudo-tumoral frontal lesion. The diagnosis was confirmed by increased plasma levels of very long chain fatty acids. His young brother had an isolated adrenal insufficiency with normal brain MRI. The frontal predominance of the lesion and the clinical polymorphism of the disease in this family are discussed.