probands

A proband is the principal individual in a family who brings a genetic disorder or condition to medical attention and from whom a pedigree or family study begins. In clinical genetics, the proband serves as the starting point for collecting family history, evaluating the phenotype, and testing hypotheses about inheritance patterns. The term helps epidemiologists and geneticists trace how a trait or mutation may segregate through a family.

Etymology and usage: The word comes from Latin probandus, meaning “to be proved.” In pedigree work, the male index case is often called propositus, the female index case proposita; in common usage, proband is used generically for either sex. The concept is closely related to the term index case, though some sources distinguish the two in specific contexts.

Role in testing and counseling: The proband’s presentation guides initial differential diagnosis and determine which relatives might be offered testing. Studying the proband and family members helps estimate recurrence risk, penetrance, and expressivity. Researchers must consider ascertainment bias, as the proband’s identification can influence apparent inheritance patterns and prevalence estimates within a family or population.

Pedigree notation: In pedigree diagrams, the proband is typically highlighted, often with an arrow, and affected individuals are shaded. Generations are labeled with Roman numerals and individuals with Arabic numbers to map relationships and inheritance.

Other uses: Outside medical genetics, proband can refer to the subject of a study or case in research, particularly in family or epidemiological investigations.