Whole-Body muscle MRI in a series of patients with congenital myopathy related to TPM2 gene mutations

Abstract

Beta-tropomyosin 2 (TPM2) gene mutations are a rare cause of congenital myopathy with variable clinical and histological features. We describe muscle involvement using Whole-Body muscle Magnetic Resonance Imaging (WBMRI) in 8 individuals with genetically proven TPM2 mutations and different clinical and histological features (nemaline myopathy, 'cap disease', Bethlem-like phenotype, arthrogryposis). Most patients shared a recognizable MRI pattern with the involvement of masticatory and distal lower leg muscles. The lower leg showed constant soleus muscle involvement, and often also involvement of peroneus, tibialis anterior, and toe flexor muscles. Pelvic and shoulder girdles, and upper limbs muscles were quite spared. Two adult subjects (a patient and a paucisymptomatic parent) had a more diffuse involvement with striking fat infiltration of the rectus femoris muscle. Two children showed variant findings: one presented with masseter involvement associated with severe axial fat infiltration, the second had masticatory and distal leg muscle involvement (soleus and gastrocnemius muscles). Our study suggests that, independently of the clinical and histological presentation, most patients with TPM2 mutations show a predominant involvement of masticatory and distal leg muscles with the other regions relatively spared. More spread involvement may be observed. This cephalic-distal MRI pattern is not frequent in other known myopathies.