The underlying mechanisms for the development of myopathy in patients with cystinosis are not fully understood but are believed to be related to the direct effects of cystine crystal accumulation in muscle cells.1
Approximately 25% to 70% of adults with cystinosis have myopathy. Myopathy can affect both proximal and distal muscles, and it typically starts with weakness in the hands and progresses to swallowing/speech dysfunction and pulmonary insufficiency.1-5
Videos explaining myopathy in the hands and throat are available to support patient education.
Distal myopathy has been described in as many as 85% of adults with cystinosis, contributing to functional limitations. Muscle atrophy and weakness in the hands can cause difficulties with activities such as gripping, buttoning clothing, and holding on to objects.5
About 40% to 75% of adults with cystinosis report symptoms of dysphagia, which can include gagging, vomiting, slow eating, choking, pain or difficulty swallowing, and dysphonic speech. Clinicians may attribute these symptoms to GI issues rather than myopathy in patients with cystinosis. However, dysphagia is important to recognize as it is a major contributor to morbidity and mortality due to risks of aspiration, aspiration pneumonia, feeding problems, and poor nutrition.2,5,8,9
Progressive myopathy also affects accessory chest muscles, causing extraparenchymal restriction of ventilation, which can be a debilitating and sometimes life-threatening complication of cystinosis.4,8
Managing myopathy in patients with cystinosis typically involves a multidisciplinary approach since myopathy varies in severity and progression and may be present even before clinically recognizable weakness. Referrals to neurology, orthopedics, pulmonology, and physical and occupational therapy may be warranted.3-5,10
Regular monitoring of muscular, pulmonary, and swallowing functions by assessment and patient reporting is important to identify and address changes as needed3,4,7
Early and consistent cystine-depleting therapy (CDT) is associated with lower frequency of myopathic complications, including swallowing and pulmonary dysfunction, and there is evidence that CDT may help prevent worsening of some symptoms. Physical therapy and exercise programs tailored to patients’ needs and abilities, including exercises that support swallowing and pulmonary function, are important to help maintain muscular strength.2,4,9-12
