Painful Leg in a Toddler: Consider Idiopathic Neuralgic Amyotrophy

Idiopathic neuralgic amyotrophy (INA) is a plexopathy with acute onset of severe pain followed by loss of muscle strength and atrophy of the muscles innervated by the involved plexus. Involvement of the brachial plexus is characteristic but occasionally the lumbosacral plexus is involved. This is denominated as ‘idiopathic lumbosacral plexus neuropathy’. INA can occur at any age. This case illustrates the diagnostic course in a toddler with an ‘idiopathic lumbosacral plexus neuropathy’. Even as a recognizable clinical picture, INA remains a diagnosis by exclusion.