Kashin–Beck disease and Sayiwak disease in China: Prevalence and a comparison of the clinical manifestations, familial aggregation, and heritability

ObjectiveTo compare the prevalence, the clinical manifestations, familial aggregation and heritability of Kashin–Beck disease (KBD) and Sayiwak disease (SD) in China.Methods10,823 people from 1361 families in 14 villages in Linyou County, Shaanxi Province, were examined for KBD, and 2264 people from 552 families in Sayiwak village, Kashi city, Xinjiang, were examined for SD. The investigation included documentation of individual information and clinical manifestations. Patients were subject to radiographic imaging of the right hand. t-Tests and chi-square tests were used to examine correlations of the diseases with age and gender in each of the two groups. Analysis of familial aggregation was conducted with the chi-square distribution analysis of goodness of fit using the SAS8.0 program. The Li–Mantel–Gart method was employed for the segregation analysis. The Falconer regression method11 was employed to estimate heritability (h2).ResultsThe prevalence of KBD in Linyou County was 10.90%, and of SD in Sayiwak village was 0.57%. Of the 21 clinical signs examined, KBD cases exhibited 19 signs (90.48%) and SD cases exhibited 18 signs (85.71%), which indicate similarities between the two diseases. However, different clinical signs were evident between the KBD and SD cases, with different impairment rates among joints of limbs in KBD and similar rates in SD. A comparison of radiological features of limb arthropathy between the two diseases showed differences in several characteristics between the two diseases. In addition, measurements of stature and sitting height showed significant differences in bone development between the two diseases. For KBD cases, the values of h2 in the first-degree and the second-degree relatives were 41.76% and 37.20% (P < 0.05). The CI of h2 was 31.17–52.38 and 19.86–54.55, with a segregation ratio of P = 0.12, SE(P) = 0.014, 95%CI 0.09–0.15, less than 0.25(χ2 = 42.36, df = 1, P < 0.001). For SD cases, the values of h2 were 155.61%, 273.63% and 236.83%. The 95% CIs of h2 were 133.20–178.12, 229.83–317.42 and 145.83–327.81, respectively, with a segregation ratio of P = 0.34, SE(P) = 0.059, and CIs between 0.22 and 0.45(χ2 = 4.9817, df = 1, P > 0.05).ConclusionThe results indicate both similarities and differences in the clinical manifestations of KBD and SD. However, environmental factors appear to play a major role in KBD, while hereditability is a major factor in SD.