Cortical Impairment, Reduced Muscle Mass Associated With Nephropathic Cystinosis

Children and young adults with nephropathic cystinosis may have cortical impairment and reduced muscle mass, according to the results of a recent study.

“With the introduction of cystine-depleting therapy with cysteamine and the possibility to survive to adulthood, new challenges of skeletal complications are a concern, with sparse data available regarding bone development,” the researchers noted.

To examine the relationship between bone density and geometry in these patients, researchers clinically evaluated 51 patients with genetically proven nephropathic cystinosis. All patients were aged between 6.6 to 39.6 years. Patient history, physical examinations, grip strength measures, and biochemical and imaging studies such as peripheral quantitative computed tomography were utilized to observe bone density, bone geometry, muscle mass, and muscle function. Age- and gender-specific reference data were compared.

Z-scores were lower than reference data for height, weight, and BMI. Medullary cross-sectional area (CSA; median [M] = 0.13, standard deviation [SD] = 1.56) and cortical density z-scores (M = -0.25, SD = 1.63) were not compromised. Cortical CSA z-scores (M = -2.16, SD = 1.08) and Strength-Strain Index (M = -2.07, SD = 1.27) were reduced. Further, reduced z-scores for muscle CSA (M = -2.43, SD = 1.27), grip strength (M = -3.01, SD = 1.10), and jump force (34% lower than reference value) indicated muscular deficits.

“Multiple regression analyses indicated an association of muscle mass with medullary CSA and SSI, but not with cortical CSA,” the researchers concluded. “While bone density parameters were normal, bone geometry was altered, resulting in a thinner cortex with possible impact on bone strength. Muscle weakness may be partially responsible for altered bone geometry and could provide a potential treatment target.”

Reference:
Pozza SBD, Lemster S, Herzig N, et al; Interdisciplinary Cystinosis Clinic. Cortical impairment and reduced muscle mass in children and adults with nephropathic cystinosis. J Bone Miner Res. Published online June 12, 2024. https://academic.oup.com/jbmr/advance-article-abstract/doi/10.1093/jbmr/zjae092/7691686?redirectedFrom=fulltext&login=false