Hereditary Neuropathy with Liability to Pressure Palsy (HNPP): An Uncommon Cause of a Common Complaint

Introduction: Limping/refusal to walk is a common complaint in the pediatric department. The differential diagnosis includes infectious, inflammatory, traumatic and neoplastic etiologies, among others. An unusual etiology, especially in the pediatric population is Hereditary neuropathy with liability to pressure palsy (HNPP), an autosomal-dominant condition of recurrent, episodic demyelinating neuropathy, presenting most commonly as acute-onset non-painful focal sensory and motor neuropathy in a single nerve. The peroneal and ulnar nerves are most frequently affected. 80% of HNPP patients carry a 17p11.2 chromosomal deletion, causing decreased expression of peripheral myelin protein 22 (PMP22).

Case presentation: We report a 4.5 years-old child, with an acute onset of nonspecific pain in both legs and refusal to walk. On physical examination, lower motor neuron signs were evident in the left leg. Spine MRI was normal, and bone scan showed decreased absorption in the left ankle. In a thorough anamnesis we discovered that the father has recurrent episodes of paresthesia and loss of sensation in his palms, and a paternal-uncle experiences similar symptoms as well as recurrent episodes of drop foot. Interestingly, in his asymptomatic younger sister`s prenatal chromosomal microarray analysis (CMA), a 17p11.2 deletion was noted. Subsequently, CMA was pursued and confirmed the diagnosis of HNPP in the proband. At least three additional affected family members are undergoing CMA.

Conclusion: This case demonstrates how a thorough anamnesis can lead us to a rare genetic etiology with a good prognosis and prevent unnecessary examinations, and underscores HNPP as an uncommon diagnostic possibility in the limping child.