Resumen: X-linked adrenoleukodystrophy is the most common peroxisomal disorder. This disease is caused by a defect in the ABCD1 gen. Saturated very long chain fatty acids are accumulated in serum, adrenal cortex and central nervous system white matter. The clinical spectrum is characterized by progressive neurological dysfunction and adrenal insufficiency with a devastating prognosis. We report a first case of X-linked adrenoleukodystrophy with fatal evolution which identified two asymptomatic family members and established a preventive treatment. Although there is no definitive cure, we stress the importance of family study and evaluation of the individual in situation of risk to establish an early preventive treatment and to give in each particular situation suitable professional advice. Idioma: Español DOI: 10.5546/aap.2017.e279 Año: 2017 Publicado en: Archivos Argentinos de Pediatria 115, 5 (2017), e279-e281 ISSN: 0325-0075 Factor impacto JCR: 0.405 (2017) Categ. JCR: PEDIATRICS rank: 118 / 124 = 0.952 (2017) - Q4 - T3 Factor impacto SCIMAGO: 0.184 - Pediatrics, Perinatology and Child Health (Q3)