Classification principles and genetics of chronic gastritis.

Two family samples, (i) a sample considered to represent the population at large (431 subjects) and (ii) a sample of first-degree relatives of index subjects (IS) with overt pernicious anaemia (183 subjects) were analyzed in order to evaluate the onset and course of chronic gastritis (CG) and the pathogenetic factors involved with special reference to the effects of genetic variation. The analysis was based on data obtained from two generations: first generation (sibs of the IS) and second (children of the IS). Formulae derived from Poisson process were used for age-correction of the gastritic changes. Otherwise, conventional statistical methods were used in the genetic analysis and the calculation of prevalences of CG. This approach enabled us to achieve a classification of gastritis into more specific subgroups and to evaluate the natural course of the disease. The progression of gastritis in the second generation (children; mean age 35 years) was roughly similar in antrum and body, indicating that gastritis starts as a diffuse process affecting both areas of the stomach to a rather similar degree. The start of CG and its progression is at least to some degree influenced by genetic factors and probably regulated by the male sex. Thus nearly all children of male IS's with a non-atrophic mucosa (normal mucosa or superficial gastritis) showed a normal mucosa suggesting the existence of a particular sex-bound, genetic mechanisms. These mechanisms may prevent or delay the progression of gastritis up to middle age, when a change in dynamics occurs leading to formation of more specific subtypes of CG. In the first generation (mean age 60 years) CG dispersed into more specific subtypes (corresponding to types A and B of Strickland and McKay and type AB of Glass) and to more advanced stages, which were connected with a higher than expected prevalence of advanced stages also in the relatives. The families of IS's with type A atrophic gastritis (AG) (severe AG in the body but no AG in antrum), type B (AG in antrum but no AG in body) and type AB AG (AG in both antrum and body) showed typical dynamic patterns of the age-specific prevalences of AG. Genetic calculations showed that the type A of AG found in pernicious anaemia patients and their relatives is inherited by a simple dominant gene, while this type of inheritance is statistically unlikely in the type B of AG. The type B, on the other hand, exhibited characteristics that indicate a recessive Mendelian inheritance.(ABSTRACT TRUNCATED AT 400 WORDS)