Primary adrenal insufficiency resulting in diagnosis of rare ABCD1 pathogenic variant in X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is a rare neurodegenerative demyelinating disorder with variable presentations. We report a case of a 32-year-old African American male with adult-onset X-ALD presenting with primary adrenal insufficiency (PAI) and marfanoid musculoskeletal features. He was initially diagnosed with PAI of unclear etiology and taking only hydrocortisone monotherapy. Further workup revealed negative 21-alpha-hydroxylase antibodies and elevated plasma very long chain fatty acids. Genetic testing confirmed the diagnosis of X-ALD resulting from novel ATP-binding cassette transports sub-family D member 1 gene (ABCD1) pathogenic variant. Evaluations for comorbidities by ophthalmology, neurology, and neuropsychiatry were insignificant. Magnetic resonance imaging of the brain and entire spine was unremarkable. There were no cardiac or eye findings to suggest Marfan syndrome and no genetic testing for Marfan syndrome was pursued. This case highlights X-ALD as a potential diagnosis of PAI and the importance of screening plasma very long chain fatty acid levels after ruling out common etiologies.