Primary myoclonus-dystonia – Often underdiagnosed entity: Report of four affected families

Introduction: Primary myoclonus-dystonia is a rare autosomal-dominant movement disorder characterized by a combination of myoclonic jerks and dystonia. We describe the clinical phenotype in the 4 affected families.

Methods: The case records of the four families affected with Primary myoclonus-dystonia attending the Neurology-Clinic were reviewed. The clinical features were analyzed and reported.

Case description: All the affected children had onset in the first decade of life. The father of one child had symptom onset in third decade of life. Myoclonic jerks affecting the upper limbs (7/7), head/neck region (5/7), trunk (2/7) or lower limbs (2/7) were the main presenting features. Dystonias were subtle and included writer’s cramp (5/7), cervical dystonia (1/7) and toe dystonia (1/7). None of the patients had behavioural problems at the point of presentation. The investigations for the secondary causes were unremarkable.

Conclusions: Primary myoclonus-dystonia is an underdiagnosed entity and raised awareness among the paediatric neurologists is required.