Chronic inflammatory demyelinating polyradiculoneuropathy presenting as predominantly sciatic monomelic neuropathy

BACKGROUND: Chronic inflammatory demyelinating polyneuropathy (CIDP) is a common yet underdiagnosed cause of potentially treatable chronic sensorimotor neuropathy. The classical form of the disease is characterised by symmetrical weakness in both distal and proximal muscle groups accompanied by sensory dysfunction and diminished tendon reflexes lasting more than 2 months. METHOD: The diagnosis of CIDP is supplemented by electrodiagnostic studies and biopsy findings confirming demyelination, in accordance with well-established diagnostic criteria. Atypical presentations of CIDP often pose a diagnostic challenge. RESULTS: In this paper, we present a case of isolated lower limb involvement due to CIDP to raise awareness of this focal lower limb variant. Of particular, significance is the use of lumbosacral plexus MRI to assist in the diagnosis. CONCLUSION: Focal CIDP is an atypical presentation that should be considered in patients presenting with chronic monomelic neuropathy and should be investigated with electrodiagnostic studies, lumbar puncture, nerve biopsy and MRI of the nerve roots and plexuses.