What Do Cranes Have To Do With Anything

The word pedigree comes from the French term pie de grue or crane's foot. The term first appeared in the English language in the 15th century. It described the curved lines, resembling a bird's claw, that were used to connect an individual with his or her offspring (Resta, 1993). Such vestiges of a bird's talons are obvious in the example of a sippschaftstafel drawn by Ernst Rudin shown in Figure 1.1. The sippschaftstafel was a form of depicting family ancestry used by German eugenicists in the...

Dominant and Recessive Inheritance Patterns A Shifting Paradigm

Historically, dominant inheritance is the term used when the heterozygote and homozygote are clinically indistinguishable. In other words, only one copy of the gene mutation or alteration is needed for clinical (phenotypic) features. Recessive inheritance traditionally describes individuals who are clinically affected when they have a double dose (homozygosity) of a gene alteration. The ability to examine gene action at the biochemical and molecular levels demonstrates that gene expression is...

The Basic Pedigree Symbols

The most common pedigree symbols are shown in Figure 3.4. The gender of an individual is assigned by the outward phenotype. This is important when drawing a pedigree for a child with ambiguous genitalia. The age (or date of birth) is noted for each individual. Record the cause of death and age at death for all individuals on the pedigree. Noting the year of death is useful because this can provide you with clues as to the diagnostic tools available during that medical era. For example, DNA...

Earlyonset Cataracts

Approximately 1 250 infants are born with a cataract (Robinson and Linden, 1993). Worldwide, 10 of all blindness is attributed to congenital cataracts (Rabinowitz et al., 1997). Cataracts seem to be involved in the aging process, for all humans will develop cataracts that can impair vision if they live to an advanced age. The upper age limit that is considered early for the onset of cataracts is debatable (R. Kalina, personal communication). Determining the significance of a family history of...

Mental Retardation

Mental retardation is not something you have, like blue eyes or a bad heart, nor is it something you are, like short or thin. It is not a medical disorder or a mental disorder . . . Mental retardation reflects the fit between the capabilities of individuals and the structure and expectations of their environment. American Association on Mental Retardation (1992) Concern about a family member with mental retardation is frequently the impetus for a person or couple to seek genetic counseling....

Triplet Repeat Disorders and the Inheritance of Dynamic Mutations

Anticipation describes the clinical phenomenon in which a genetic condition seems to worsen over successive generations. For example, a child with myotonic dystro phy may have severe hypotonia and failure to thrive, yet the affected grandparent has only early balding and pre-senile cataracts. Anticipation has mostly been described in autosomal dominant neurological disorders, such as Huntington disease, the spinocerebellar ataxias, and myotonic dystrophy (La Spada et al., 1994). In these...

Neurological And Neuromuscular Disorders

Molecular diagnosis is creating an upheaval in the classification systems of genetic neurological diseases. The spinocerebellar ataxias are now classified by at least seven subtypes depending on the molecular etiology. The nomenclature flip-flops back and forth between the hereditary motor sensory neuropathies (HMSN) and the subtypes of Charcot-Marie-Tooth (CMT) as molecular diagnosis refines the phenotypes. Many of the forms of muscular dystrophy can now be distinguished by molecular testing....

The Ultimate Pedigree Challenge

The following fictitious family history is provided for you to practice drawing each standardized pedigree symbol. This teaching scenario is republished with permission from the American Journal of Human Genetics (Bennett et al., 1995). The answer is in Appendix A.1. The consultand, Mrs. Feene O'Type, presents to your office with a pregnancy at 16 wk gestation. She has questions about risks to her fetus because of her age. She is 35 years old and her husband, Gene O'Type, is 36 years old. Mrs....

Whats Remarkable About An Unremarkable Family History

Many times when you take a family history, there are no obvious genetic diseases or familial aggregation of disease. Table 3.4 reviews some common reasons that a family history of a genetic condition is missed. Clinicians often note in the medical record that the family history is negative or the person has no family history. I prefer stating the family history is unremarkable or noncontributory. The word negative may be misconstrued as a value judgment. All humans have a family history, though...

Physical Birth Anomalies And Variants

A family history of birth defects is usually a major concern to a couple making reproductive choices. It is not unusual to encounter a family history of a significant birth defect an estimated 3 of newborns have one or more major physical anomalies. As many as 1 3 of congenital anomalies are characterized as being genetic in origin. Known environmental teratogens (see Table 3.2) are surprisingly few, and they are implicated as causal factors in approximately 1 400 birth anomalies (Winter et...

Pedigree Symbols Related to Pregnancy and Reproduction

The various pedigree symbols related to pregnancy, spontaneous abortion, termination of pregnancy, stillbirth, and infertility are shown in Figure 3.5. Always include the gestational age, in weeks (wk), if known, below the symbol. An approximation of dates can be shown, such as 12 wk. Usually the gestational age is stated as the date of the last menstrual period (LMP) or the estimated date of confinement (EDC). Some clinicians prefer using EDD (estimated date of delivery) because the...

The Pedigree as a Diagnostic Tool

Reviewing a family pedigree can aid the clinician in diagnosis. For example, in making a diagnosis of a familial cancer syndrome it is imperative to know the cluster of types of cancers the ages of the individuals diagnosed with cancer and how closely the individuals with cancer are related to each other (i.e., first- as compared to second-degree relatives). The family history will even influence the kind of genetic diagnostic tests that are ordered. Take, for example, the family history of...

Laying The Foundation Pedigree Line Definitions

Pedigrees can become quite complicated when they include multiple generations. Add to this the common occurrence of a person having children with multiple partners, and a pedigree soon looks like a television-wiring diagram There are four main line definitions which form the trunk and branches of a medical family tree (Fig. 3.1). Here are some simple rules to remember A relationship line is a horizontal line between two partners a slash or break in this line documents a separation or divorce....

Creating A Medical Pedigree Getting Started

The basic medical pedigree is a graphic depiction of how family members are biologically and legally related to one another, from one generation to the next. Each family member is represented by a square (male), or a circle (female), and they are connected to each other by relationship lines. This family map is meaningless if the symbols cannot be interpreted from clinician to clinician. The symbols outlined here are from the 1995 recommendations of the National Society of Genetic Counselors...

The Approach Look For The Rare But Remember The Ordinary

Patients and family members often inquire about the heritability of common medical conditions. This chapter provides suggestions for directed family history questions related to many of the everyday medical diseases encountered in the typical family history. By supplementing general family history screening questions (as reviewed in Chapter 3) with a more targeted query, the clinician can probe deeper into the medical-family history and identify individuals who may benefit from a more extensive...

Illustrations and Tables

A hypothetical pedigree representative of a family with von Hippel-Lindau syndrome. The Family Tree, quilt. Representative pedigree of autosomal dominant (AD) inheritance. Representative pedigree of autosomal recessive (AR) inheritance. Representative pedigree of an X-linked recessive condition (XLR). Pedigree suggestive of an X-linked mutation that is lethal in males. Representative pedigree of X-linked dominant inheritance. Representative pedigree of multifactorial inheritance. Representative...