Introduction: X-linked adrenoleukodystrophy , a genetically determined rare peroxisomal disorder, results from pathogenic mutations in the ABCD1 gene. This leads to the accumulation of very-long-chain fatty acids in the brain, spinal cord, and adrenal glands primarily . Major clinical manifestations arise from progressive cerebral demyelination and adrenalinsufficiency . Bone marrow transplantation and gene therapy performed before neurological deterioration have improved survival and overall prognosis. Case presentation: We report an 8-year and 10-month-old boy who presented to thepaediatric endocrinology clinic at National Hospital Galle with progressive isolated generalised hyperpigmentation for three years. He was the firstborn of nonconsanguineous parents with one younger sibling. His condition later progressed with rapid behavioural and neurocognitive impairment. There was a strong family history among male relatives with diagnostic uncertainty . Biochemical evaluation was compatible with primary adrenal insufficiency , demonstrated by ACTH levels >2000 with low serum cortisol and a low aldosterone/renin ratio. Normal serum electrolyte concentrations, vitamin B12, gonadal hormones, and 17-hydroxyprogesterone levels helped to rule out other possible causes and raised suspicion of X-ALD. Neuroimaging of the brain showed early white matter and basal ganglia involvement. The diagnosis was confirmedby genetic analysis. His management was optimized through a multidisciplinary approach. Conclusion: This case emphasizes the multigenerational burden of unrecognized X-ALD with increased morbidity and mortality . Timely diagnosis and follow-up with serial neuroimaging before significant neurological decline permits successful haematopoietic stem cell transplantation and aid to minimize the devastating disease status. Long-term management of X-ALD includes carrier detection combined with reproductive and genetic counselling.