The little girl my husband and I may be adopting from Kazakhstan was taken away from her mother because her mother was diagnosed with oligophrenia and was unable to care for her. This scares me because I teach mentally handicapped children and I know many of them have low IQ parents. I also know that environment is a factor. The little girl is almost two and she is described as having normal development. What are the chances of oligophrenia being hereditary?
The term “Oligophrenia” is usually used to mean mentally deficient. It is an unfortunate term because it is very broad and prone to misuse. Mental retardation has a number of etiological, or causal, factors. Unfortunately, in about 40 percent of cases, we never find out the etiology after a thorough investigation. Mental retardation occurs in about 2-3 percent of the general population, but will be higher in less developed nations. The chances of a genetic cause for mental retardation are therefore very hard to say. It would be reasonable to assume perhaps that if someone suffered some perinatal insult (lowered oxygen levels in the unborn infant) that their retardation would be secondary to that insult.
A number of single gene disorders can result in mental retardation. Many of these are associated with atypical or dysmorphic physical characteristics. Such conditions include Fragile X syndrome, neurofibromatosis, tuberous sclerosis, Noonan’s syndrome and Cornelia de Lange’s syndrome.
As many as one fourth of persons with mental retardation will have a detectable chromosome abnormality. Children with Down syndrome are usually very recognizable, but others such as Klinefelters may not be as noticeable. Other children may have a small deletion that is usually not reported. Some chromosome abnormalities can be inherited, but most occur de novo– meaning that they pop up in that individual, but that they would not pass it on to their offspring.
As with many things in life, there are no simple answers. However, knowing the increased incidence problems that happen to young children in that part of the world, it is likely that the mother’s problem was the result of some perinatal insult or a confluence of many factors. But it would be difficult or impossible to give you a very reliable odds estimate.
On the bright side, a knowledgeable examiner should be able to give an idea about this individual child. The statement “normal development” means little to me unless it’s placed in the proper context. What is the child’s head circumference? Were there any delayed milestones? Does the child have imaginative play? When did she enter the institution, and how long has she been there? In reality, every child available for adoption has a risk. It is the job of the doctor to give you a report of what the risks are. To do a good job we try to review as much information as we can possibly get, but unfortunately we are limited to the information provided.