A Genetically Transmitted, Benign Habit: A Case Report and Review

Habits are defined as acquired, repetitive, involuntary and body focused, stereotyped motor acts. Tics have the same attributes, but are characterised by muscle spasm additionally. So far, the emphasis in the literature is that the habits are acquired. There is no reference in the literature as to the habits being transmitted genetically. Whereas in the case of tics, some like, Tourette Syndrome (TS), are accepted to have genetic basis Habits are harmless. But some are self - destructive Out of the group of the four destructive habits, like trichotillomania (TTM), bruxism, scabiomania or skin pulling (SP) and onychophagia, TTM, along with chronic persistent motor tics, persistent vocal tics and combined motor and vocal tics like TS, are grouped together, as habit disorders by the American Psychiatry Association (APA) Statistical Manual of Mental Disorders classification, 4th edition (DMS 4). Virginia Commission recommends inclusion of SP also under habit disorders. Other authors include all the four destructive habits under the habit disorders. It is also accepted that habits are related to behavioural patterns and that the behavioural patterns are genetically determined. Thus an indirect link is established between the habits and heredity, through behaviours. The author presents in this article, a benign, ‘nose rubbing habit’ being transmitted through 6 generations in a family tree. Unique to the pattern of inheritance, 100 % desendents in some generations (generations 1,2 and 3) with involvement of both males and females, without any skip generations, is seen .Very early onset is recorded at the age as low as 2 years and as high as 6 years belonging to the in the 6th generation. This is the first of it’s kind reported in literature that a benign habit is shown to run in a family, across 6 generations. This is contrary to the popular belief, that habits are always acquired. If it is so, what is it that irrefutably transmitted through 6 generations in this case? Mitochondrial gene (mtDNA) transmission, involving recombinant maternal and paternal mtDNA, is suggested, by inference and after eliminating the other Mendalean and non Mendalean types of inheritance. Of course, the main intended focus of the article is to highlight the transmission of a habit- trait (?) genetically. As a possible explanation of this observed phenomena only, the tentative inheritance pattern is suggested. The matter is open for discussion by the concerned fraternity.