Clinical perspectives on myopathic complications in nephropathic cystinosis

Abstract Patients with nephropathic cystinosis are now living into their 50s and beyond thanks to advances in medical management. Due to this shift in the natural history of the disease, monitoring for and addressing extrarenal manifestations, including myopathy, has emerged as an area of increasing importance. Muscle involvement typically begins before the onset of noticeable symptoms, and evidence suggests that subtle signs may even emerge in childhood. The origin of muscle involvement in cystinosis has not fully been elucidated and is likely multifactorial. Nonetheless, cellular toxicity due to intralysosomal cystine accumulation appears to be a key catalyst. Myopathy in cystinosis, which can lead to muscle weakness, dysphagia, and pulmonary dysfunction, contributes to significant morbidity and mortality, including impaired quality of life, reduced ability to independently perform activities of daily living, feeding difficulties and malnutrition, choking, and aspiration. Nephrologists typically act as the de facto primary cystinosis providers and are tasked with screening for muscle involvement and coordinating multispecialty referrals to neurology, pulmonology, gastroenterology, and physical, occupational, and speech therapy. In this review, we aim to summarize the current understanding of myopathy in nephropathic cystinosis and discuss strategies to support monitoring, assessment, management, and mitigation of this complication, as well as specialist referral and coordination.