title: Estimating sex ratio biases in X-linked disorders: is there an excess of males in families with X-linked ichthyosis?
abstract: We derive the conditional probabilities for estimating the sex ratio in families ascertained through affected males for the study of X-linked recessive diseases. These conditional probabilities correct for the fact that the probability that a family will be ascertained increases with the number of males in the family. Data from four published studies for X-linked ichthyosis vulgaris are analyzed, three having an excess of males and one having a highly statistically significant excess of males. It is not known if this difference in the two samples represents a biological difference between the two populations or an unrecognized ascertainment bias.
mesh_terms: D005260:Female; D005808:Genes, Recessive; D008040:Genetic Linkage; D006801:Humans; D007057:Ichthyosis / Q000235:genetics*; D008297:Male; D011336:Probability; D012730:Sex Chromosomes; D012744:Sex Ratio; D014960:X Chromosome