Case Report: Bilateral pes planovalgus: an uncommon pediatric orthopedic presentation of Charcot–Marie–Tooth disease type 4B1

Abstract

Charcot–Marie–Tooth (CMT) disease is an inherited motor and sensory neuropathy that typically presents with cavovarus foot deformity. Pes planovalgus is uncommon in CMT and, while noted incidentally in multicenter cohort studies of CMT4B subtypes, has not been described as the predominant orthopedic manifestation in a published case report of genetically confirmed CMT4B1. We report the case of a 7-year-old girl who presented with progressive painful bilateral pes planovalgus, hallux valgus, frequent falls, and gait imbalance, despite otherwise normal developmental milestones. Neurological examination revealed globally reduced deep tendon reflexes, absent ankle jerks bilaterally, and distal sensory impairment in a length-dependent distribution. Electrodiagnostic studies demonstrated a severe mixed demyelinating and axonal polyneuropathy with completely absent distal motor and sensory responses in the lower limbs. Genetic analysis identified a pathogenic MTMR2 variant, confirming the diagnosis of autosomal recessive CMT type 4B1. Weight-bearing radiographic evaluation demonstrated bilateral collapse of the medial longitudinal arch, forefoot abduction, and hallux valgus deformity. The patient was managed in a multidisciplinary setting with physiotherapy, occupational therapy, and orthotic support. Conservative management resulted in satisfactory clinical improvement on the left side; however, the right foot demonstrated persistent pain and functional limitation despite adequate conservative treatment. Surgical correction of the right foot has been planned, including Evans lateral column lengthening osteotomy, medial talonavicular capsule plication, and Tendo-Achilles lengthening, with possible medial midfoot closed wedge osteotomy and flexor tendon release. This case illustrates phenotypic variability within CMT4B1. In contrast to her older brother, who carries the same MTMR2 variant and developed the classic cavovarus deformity, our patient presented with early progressive pes planovalgus, broadening the recognized phenotypic spectrum of this rare subtype. Recognizing this variant presentation is essential to avoid misdiagnosis and to prompt timely neurological, genetic, and orthopedic evaluation in children presenting with painful flatfoot and signs of peripheral neuropathy.