Bent spine syndrome as an initial manifestation of late-onset multiple acyl-CoA dehydrogenase deficiency: a case report and literature review

Background: Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) is an autosomal recessive inherited disease of metabolic dysfunction clinically characterized by fluctuating proximal muscle weakness, excise intolerance, and dramatic riboflavin responsiveness. Dropped head syndrome can occasionally be observed in some severe patients with late-onset MADD; however, bent spine syndrome as an initial symptom had not been reported in patients with late-onset MADD. Case presentation: A 46-year-old man lost the ability to hold his trunk upright, and had difficulty in raising his head, but he had no obvious symptoms of limb weakness. Meanwhile, he developed persistent numbness of limbs and lips around. Myopathological features and combined elevation of multiple acylcarnitines indicated that the axial myopathy might be caused by lipid storage myopathy. Cervical and lumbosacral MRI revealed a lot of abnormal signals diffusing along paravertebral muscles, while the abnormal signals almost disappeared after riboflavin treatment. Nerve conduction study indicated the patient suffering from predominantly sensory neuropathy and mildly motor neuropathy. Muscle pathology also demonstrated no typical neurogenic change, which was consistent with the electrophysiological findings. Causative mutations were found in the ETFDH gene. Conclusion: We report the first case of late-onset MADD with sensory neuropathy initially manifesting as bent spine syndrome and dropped head syndrome.