Grip Strength in Adults and Children with Cystinosis

Abstract

Background: Chronic kidney disease (CKD) is associated with impaired muscle strength. Cystinosis patients have increased risk for impaired muscle strength due to early development of CKD and cystinosis-induced myopathy. This study assesses muscle strength in cystinosis patients and investigates risk factors of decreased muscle strength. Methods: Adult and pediatric patients were recruited from Cystinosis Research Network conferences and a large pediatric nephrology clinic between 2017 and 2019. Patients and caregivers completed questionnaires on demographic characteristics, disease course, daily physical activity, and neuro-muscular symptoms. Grip strength was assessed using a dynameter and calculated z-scores for age and sex were assessed for associations with patient characteristics. Results: We included 76 patients with a mean grip strength z-score of -2.1 (SD 1.1), which was lower than seen in CKD patients without cystinosis. Male sex and delayed cysteamine initiation were independently associated with impaired grip strength. Among adults, a low level of physical activity was associated with lower grip strength z-score, but no association was found in children. A third of the patients reported neuro-muscular symptoms, with swallowing issues associated with lower grip strength. There was no significant correlation between eGFR and grip strength z-score. Conclusion: Cystinosis patients have impaired muscle strength compared to healthy controls and CKD patients. This impairment is greater in male patients and in patients with late initiation of cysteamine therapy, and is associated with lower physical activity. Further studies investigating the effect of different types of physical activities, optimizing cysteamine therapy and other interventions are needed.

Assessment of Undernutrition in Pediatric Chronic Kidney Disease - Gaps and Opportunities

“…It has proven to be an inexpensive, prognostic biomarker of stratifying cardiovascular mortality in a large prospective adult population study ( 37 ). In children, there is emerging evidence of impaired muscle strength in those with CKD with an underlying non-glomerular disease in particular, and impaired muscle strength noted is independent of growth retardation or body mass index ( 38 , 39 ). However, unlike in adults, a strong association of physical activity to muscle strength in children with CKD has not been well established.…”