X-chromosome inactivation patterns in blood. A) Distribution of XCI patterns among non-carrier females (n = 41), asymptomatic carriers (n = 40) and symptomatic carriers excluding patients presenting only myalgia (n = 18). For each group, the five parameters are the lowest observation, lower quartile, median, upper quartile, and highest observation. B) Distribution of XCI patterns among symptomatic carriers according to clinical phenotype. Individual XCI data, mean and standard deviation are shown. The extent of XCI skewing in blood tended to increase with increasing severity of muscle symptoms.