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Pain study in X-linked adrenoleukodystrophy in males and females

Valeria Bachiocco¹, Marco Cappa², Anna Petroni¹³, Ettore Salsano⁴, Carla Bizzarri², Ilaria Ceccarelli¹, Gabriele Cevenini⁵, Viviana Pensato⁴ and Anna Maria Aloisi¹³

1 University of Siena, Department of Medicine, Surgery and Neuroscience, Siena, Italy; 

2 Bambino Gesù Children’s Hospital, IRCCS Rome, Italy

3 Biomedicine and Nutrition Research Network, Via Paracelso 1, 20129 Milan, Italy

4 Neurological Institute Carlo Besta, IRCCS Milan, Italy

5 University of Siena, Department of Medical Biotechnology, Siena, Italy

Abstract

X-linked adrenoleukodystrophy (ALD) is a metabolic disorder in which very long chain fatty acids (VLCFAs) are accumulated in the nervous system and adrenal cortex, impairing their functions. Three main variants are described in males: adrenomyeloneuropathy (AMN), a cerebral form (cALD or cAMN) and Addison disease only (AD), while for females no classification is used. Chronic pain occurrence and sensory phenotype profile were assessed in 30 patients (20 males: 10 AMN, 1 cAMN, 1 cALD, 8 AD, and 10 females). A set of instruments assessed the intensity, quality and extent of pain, while a battery of Quantitative Sensory Testing (QST) procedures examined the functional status of Ab and Ad fibers. Principal component analysis and hierarchical clustering with sensory responses input were used to identify distinct clusters.

Nearly half of the subjects reported pain, with high prevalence in females and male AMN patients. No sex differences in pain dimensions were found. The sensory responses were heterogeneous, differing among the clinical variants and between genders. Male AMN/cAMN/cALD patients showed the worst impairment. Ab and Ad fibers were affected in males and females, but Ab fibers appeared undamaged in females when tactile sensitivity was tested. Abnormal responses were localized in the lower body district, according to the dying-back pattern of the neuropathy. Cluster analysis showed discrete clusters for each function examined, with well-interpretable sensory and clinical phenotypes. The study of pain and of the sensory profile appears to indicate a difference in the mechanisms underlying the AMN/cAMN /cALD and AD clinical forms and in the treatment of the respective generated pains.