Chronic motor axonal neuropathy.

The identification of a distinct subgroup of patients within the spectrum of lower motor neuron syndromes (LMNS) is crucial as some are potentially treatable. We describe the clinical and neuropathological characteristics of a patient presenting with a rapidly progressive LMNS associated with high titers of anti-GM1 antibodies, leading to respiratory failure within 10 months. Histopathological study of a biopsy of a obturator nerve motor branch demonstrated a predominantly axonal motor neuropathy, while electron microscopy analysis localized macrophages located within the periaxonal space. Immunohistochemistry demonstrated deposits of complement activation products (C3i) and immunoglobulins (IgM) on nerve fibers. The patient's clinical, immunological and pathological findings are consistent with a diagnosis of a chronic motor axonal neuropathy (CMAN), likely of immune-mediated origin.