Juvenile muscular atrophy of distal upper extremity associated with airway allergy: Two cases successfully treated by plasma exchange

Abstract 

Juvenile muscular atrophy of the distal upper extremity (JMADUE) is postulated to be a type of flexion myelopathy. However, patients with typical clinical features of JMADUE but without evidence of flexion myelopathy have been reported. We recently reported a significant association of JMADUE with airway allergy. Here we report the successful treatment by plasma exchange (PE) of two patients with both airway allergy and JMADUE without evidence of flexion myelopathy. Patient 1 had a 5-year history of allergic rhinitis and high titers of mite antigen-specific IgE, and patient 2 had an 8-year history of pollinosis and high titers of cedar pollen-specific IgE. Both patients noted progressive distal muscle atrophy and weakness of the upper extremities: patient 1 for 3 months and patient 2 for 3 years. Neurologically, both showed asymmetric intrinsic hand muscle atrophy, oblique atrophy of the forearm muscles, and weakness and contraction fasciculation (minipolymyoclonus) of these muscles without any sensory impairment. Neither had any evidence of flexion myelopathy on magnetic resonance imaging (MRI) in a flexed position. Both were subjected to PE three times. Soon after the PEs, both showed improvement of distal muscle weakness of the upper extremities and marked reduction of contraction fasciculation of the forearm muscles. Patient 1 showed marked reduction in ongoing denervation potentials in the distal muscles on needle electromyography, while patient 2 showed marked improvement of F wave persistence of bilateral median and ulnar nerves. Serum total and allergen-specific IgE decreased after PEs in both patients. PE was thus considered to be effective in these two patients having JMADUE without evidence of flexion myelopathy. These observations may suggest the involvement of an immune-mediated process in the neural damage of JMADUE without evidence of flexion myelopathy, especially in patients with atopic diathesis, and may support the notion that JMADUE is etiologically heterogeneous.

Keywords:  Muscle atrophy, Plasma exchange, Atopy, Motor neuron, Flexion myelopathy