A Finnish team has described a congenital myopathy linked to atypical TPM2 or TPM3 in seven patients from three families.
- In contrast to the phenotype of nemalin myopathy with weakness and hypotonia usually associated with TPM2 or TPM3 mutations, the patients presented with muscular hypertonia that could go as far as trismus and/or lead to retractions (Achilles tendon, hip and lumbar muscles), generating fatigue or stiffness that penalized their daily activities.
- On their muscle biopsies, most had no rods, and one had a few cores and minicores.
- The tropomyosin variants involved all retained their actin contact sites, resulting in a hypercontractile molecular phenotype.
