Talocalcaneal coalition in Muenke syndrome: report of a patient, review of the literature in FGFR-related craniosynostoses, and consideration of mechanism

Abstract

Muenke syndrome is an autosomal dominant craniosynostosis syndrome resulting from a defining point mutation in the Fibroblast Growth Factor Receptor3 (FGFR3) gene. Muenke syndrome is characterized by coronal craniosynostosis (bilateral more often than unilateral), hearing loss, developmental delay, and carpal and/or tarsal bone coalition. Tarsal coalition is a distinct feature of Muenke syndrome and has been reported since the initial description of the disorder in the 1990s. Although talocalcaneal coalition is the most common tarsal coalition in the general population, it has never previously been reported in a patient with Muenke syndrome. We present a 7-year-old female patient with Muenke syndrome and symptomatic talocalcaneal coalition. She presented at the age of 7 with limping, tenderness and pain in her right foot following a fall and strain of her right foot. She was treated with ibuprofen, shoe inserts, a CAM walker boot, and stretching exercises without much improvement in symptoms. A computed tomography (CT) scan revealed bilateral talocalcaneal coalitions involving the middle facet. She underwent resection of the talocalcaneal coalitions, remaining pain-free post-operatively with an improvement in her range of motion, gait, and mobility. This report expands the phenotype of tarsal coalition in Muenke syndrome to include talocalcaneal coalition. A literature review revealed a high incidence of tarsal coalition in all FGFR related craniosynostosis syndromes when compared to the general population, a difference that is statistically significant. The most common articulation involved in all syndromic craniosynostoses associated with FGFR mutations is the calcaneocuboid articulation.

Figure 1

Figure 1a: Lateral Computed Tomography (CT) view of right foot showing the talocalcaneal coalition (white arrow) Figure 1b: Axial Computed Tomography (CT) view of right foot showing the talocalcaneal coalition (white arrow) Figure 1c: 3D Computed Tomography (CT) view of right foot showing the talocalcaneal coalition (white arrow)

Figure 2

Figure 2a: Plantar axial Computed Tomography (CT) view of left foot showing the talocalcaneal coalition (white arrow) Figure 2b: Dorsal axial Computed Tomography (CT) view of left foot showing the talocalcaneal coalition (white arrow) Figure 2c: Plantar oblique 3D Computed Tomography (CT) view of left foot showing the talocalcaneal coalition (white arrow)