Childhood Onset Familial Nemaline Rod Myopathy: A Report of Two Siblings

Abstract

Aims: Nemaline rod myopathy (NRM) is a rare form of congenital myopathy characterized by slowly progressive or non progressive muscle weakness and pathognomonic rod-like structures within the muscle fibers. Muscle weakness and hypotonia are apparent from the neonatal period. We report a rare presentation of NRM seen in two siblings with similar symptoms. Both had slender physique, delayed motor milestones including delayed walking, normal language and cognitive milestones, difficulty in fast movements and change of posture, difficulty in getting to standing from sitting posture and slowly progressive weakness and positive family history. Study Design: Two siblings i.e. a brother and sister with provisional diagnosis of Nemaline Rod Myopathy were tested for all relevant diagnostic protocol with results analysed and discussed. Place and Duration of Study: Department of Physiology, Pt. B.D. Sharma Post-Graduate Institute of medical Sciences, University of Health Sciences, Rohtak, Haryana, India. Methodology: Investigations included CPK levels, motor-sensory conduction velocities, EMG studies, Muscle biopsy, MGT (Modified Gomori´s Trichrome) stain and histo-chemistry studies. Results: CPK levels were raised (279U/l) with myopathic pattern of EMG with decreased motor unit potentials, recruitment with markedly decreased amplitude; mild decrease in motor conduction velocity in tibial-peroneal nerves in both with decreased ulnar nerve sensory conduction velocity in the girl and positive muscle biopsy; diagnosed as Nemaline Rod myopathy. Conclusion: Nemaline myopathy should be suspected in children with generalized hypotonia and progressive muscle weakness along with delayed motor milestones. This report highlights the importance of EMG and conduction velocity studies along with histo-chemistry and ultra-structural examination in diagnosis of NRM in absence of availability of genetic studies.