A benign form of congenital anterolateral bowing of the tibia associated with ipsilateral polydactyly of the hallux: case report and literature review.

Congenital anterolateral bowing of the tibia is generally considered a precursor of congenital pseudarthrosis of the tibia (CPT), which is usually associated with neurofibromatosis type 1 (NF1), a common autosomal dominant genetic disorder. In many cases, NF1 is initially suspected following the presentation of a child with anterolateral tibial bowing. The prognosis of CPT is poor, and amputation may be required. Congenital anterolateral bowing of the tibia combined with ipsilateral polydactyly of the hallux (CABTP) is a rare entity that resembles the anterolateral tibial bowing that occurs in association with CPT, and may be misdiagnosed as NF1. However, spontaneous correction of the tibial bowing with an almost normal fibula has been described in all previously reported cases. Here, we report three patients with CABTP and discuss the physical and imaging characteristics and follow-up results. We suggest that given the spontaneous resolution of bowing, the absence of neurocutaneous signs and the relatively favorable prognosis, CABTP is a distinct entity that merits its own place within the field of anterolateral bowing of the tibia and has no association with CPT or NF1. This should help avoid unnecessary investigations and interventions for NF1. This article shows for the first time tibial duplication in the area of bowing, with two medullary canals surrounded by well-defined cortex on CT.