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Acetazolamide can improve symptoms and signs in ion channel-related congenital myopathy
  1. Emma Matthews1,
  2. Louise Hartley2,
  3. Richa Sud3,
  4. Michael G Hanna1,
  5. Francesco Muntoni4,
  6. Pinki Munot4
  1. 1MRC Centre for Neuromuscular Diseases, UCL and National Hospital for Neurology and Neurosurgery, London, UK
  2. 2Department of Paediatric Neurology, University Hospital of Wales, Cardiff, UK
  3. 3Neurogenetics Unit, Institute of Neurology, London, UK
  4. 4Dubowitz Neuromuscular Centre and MRC Centre for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
  1. Correspondence to Dr Emma Matthews, MRC Centre for Neuromuscular Diseases, UCL and National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; emma.matthews{at}ucl.ac.uk

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Introduction

Sarcolemmal voltage-gated sodium and calcium ion channels are essential for generating action potentials and excitation contraction coupling required for muscle contraction. Autosomal dominant sodium and calcium ion channel gene disorders cause episodic symptoms of periodic paralysis (PP) and myotonia.1 Acetazolamide treatment improves these symptoms.2 Recently, recessive congenital myopathies due to compound heterozygous or homozygous ion channel gene mutations have been described with fixed muscle weakness and disability.3 4

In case series we previously reported, two individuals with ion channel-related congenital myopathy had additional discrete episodic or fluctuant weakness causing added morbidity.3 4 Here, we delineate the long-term benefit of treatment with acetazolamide for these individuals and discuss the implications for genetic diagnosis and management of future cases.

Case 1

A 16-year-old girl with compound heterozygous SCN4A gene mutations (figure 1B).3 Reduced fetal movements were noted during pregnancy with a breech presentation at birth. Features of congenital myopathy included neonatal hypotonia, weak cry, talipes, thin muscle build and weak suck requiring nasogastric tube feeding for 12 days. With maturity, significant proximal and axial weakness occurred with difficulties running, going upstairs, rising from the floor and walking long distances. Due to respiratory insufficiency, she required nocturnal BiLevel Positive Airway Pressure (BiPAP) from age 6. Progressive scoliosis required surgical fixation at age 12.

Figure 1

Outcome measures, family trees and pictorial representation of skeletal muscle voltage-gated sodium and calcium channels with mutations marked. (A) Summary of functional and respiratory measures pre-acetazolamide (ACZ) and post-acetazolamide …

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