[Endocrine disease in adrenoleukodystrophy]

Abstract

X-linked adrenoleukodysrophy is the most frequent genetic disorder affecting central and peripheral nervous system myelin. One of the biochemical abnormalities is the accumulation of very long chain fatty acids (VLCFA) in tissues and body fluids subsequent to defective catabolism in the peroxysomes. The principal characteristic of the disease is an association between a neurological disorder and an endocrine disorder: primary adrenal insufficiency and testicular failure. Clinical manifestations are variable. There are two main forms, one affecting boys between the age of 5 and 10 years with severe rapidly fatal cerebral involvement, and the other affecting young adults between the age of 20 and 30 years with degeneration of the anterior and posterior long spinal cord tracts, similar to the disorders observed in multiple sclerosis. About 20% of the heterozygous women may develop a syndrome which resembles adrenomyeloneuropathy, rarely adrenal insufficiency. Adrenal insufficiency is present in 85% of the childhood cerebral forms and in about 70% of the adult forms. It may occur before, after or at the same time as the neurological disease but is not correlated with the severity of the neurological disorder. Careful screening is required to avoid missing subclinical forms. Adrenoleukodystrophy should be envisaged in young boys with primary adrenal insufficiency, accounting for about 30% of the cases of primary adrenal insufficiency in children under 3 years of age and about 13% of those in adults. Experience with dietary therapy (low-VLCFA diet and supplementation with unsaturated fatty acids such as glyceryl trioleate (GTO) and glyceryl trierucate (GTE), commonly called Lorenzo's oil) has not demonstrated any clinical improvement in the cerebral forms. Bone marrow transplantation is recommended for children who show early evidence of cerebral involvement. Gene therapy is a promising perspective. Lovastatin and 4-phenlbutyrate have recently been shown to normalize plasma VLCFA levels. Their therapeutic efficacy must be assessed in a randomized trial.