For each feature we provide a preferred term and use a standard format to provide a definition and description of how to observe and measure (where possible) the feature. For many of the terms, both subjective and objective definitions of terms are provided. When an objective assessment can be made, this is always preferable to the subjective. A few terms have multiple alternative objective definitions. Typically, this reflects multiple sets of norms for a quantitative trait and, in such cases, each definition is equally valid.
Our aim is to formalize, unify, and standardize the approach to clinical assessment in the hope that it will become generally accepted and applied. For each term we have added relevant comments and synonyms, and indicated terms that should no longer be used. Most clinicians have at least a few terms of which they are inordinately fond. In spite of these personal biases, our goal is to make a universal language to describe morphology. We have avoided terms that indicate pathogenesis or an active process; we aspired to simply describe what can be observed.
We recognize that a number of terms in common usage may be considered pejorative in some or all cultures. We have created alternative descriptors in these cases, even if they are not in current common usage. The definitions are intended to be applied broadly, thus we avoided obscure terms, flowery language, etc. We have tried to apply a standard format that would be readily understandable by a medical student who has completed training in physical diagnosis.
In addition to standardized terms and definitions, we aimed to provide clear illustrations of each feature. We have used our joint collection of pictures and the extensive Robert J. Gorlin slide collection which is the series of digitalized slides that Prof Gorlin gathered during his long career available to one of us (RCMH). It is important that readers recognize that a given photograph may include multiple findings. Where possible, photographs have been cropped to avoid showing other signs and to emphasize one feature. We tried to show variable expression of the features, both mild and severe.
The terms are intended for clinical evaluation of the individual using observation, palpation, or simple morphometric techniques (such as measuring of inner canthal distance). We provide basic general principles for measuring each of the body parts, and indicate in the definitions if a reliable measurement is possible and if norms are available. However, extensive description of morphometric techniques is outside the scope of this effort and readers should consult authoritative sources for this information (Farkas L Anthropometry of the Head and Face in Medicine. Elsevier, 1981; and Hall JG, Allanson JE, Gripp KW, Slavotinek AM. Handbook of Physical Measurements, 2nd Edition, OUP, 2007). We have referenced the most important standards for each of the body parts. The present project was not intended to generate new normative data, novel objective assessment techniques, or novel morphologic features. We acknowledge a tremendous lack of data on ethnic groups other than Caucasian, and we encourage efforts to address this deficiency.
The use of radiographs as part of morphologic assessments (such as a hand radiograph to distinguish a broad thumb from a bifid thumb) was controversial in the group. Although we decided not to use radiographic findings in the definitions and only use data obtained through surface examination, this issue will need to be re-evaluated.
We provide only limited and general anatomical background and have avoided more substantive explanations and reviews of what is known (or hypothesized) about the mechanism of the genesis of the physical findings. This is for several reasons. First, other excellent texts provide thorough discussions of this topic (Sadler TW, Langman J Langman's Medical Embryology 8th Ed, Lippincott Williams & Wilkins, 2000; Moore KL, Dalley AF Clinical Oriented Anatomy, 5th Ed, Lippincott Williams & Wilkins, 2005). Second, our understanding of the genesis of an anatomical finding is likely to change over time, and we did not want the definitions to change should this occur. Third, the current debate about the proposed genesis of many of the findings could detract from the intended goals of this work.
We emphasize that the terms deliberately avoid any commentary about normal or abnormal status, even when this is obvious (such as a proboscis). This is because many morphological findings are commonly observed as isolated features in the normal population. There can also be a remarkable difference in frequency of a finding among various populations. The objectively determined findings are by definition abnormal in a normative, statistical sense. However, even in these cases, the individual should simply be considered to have the feature, and no judgment of normal or abnormal status is made.
We have elected not to provide differential diagnoses for the features as such lists could be very long or incomplete. Syndromes are typically diagnosed by combinations of features, and therefore differential diagnoses of single features are of limited utility. Readers should consult databases of medical dysmorphology for this information (London Dysmorphology Databases, version 1.0.14, 2008; POSSUM web version 2008).
Bundling is a word we have used to describe a term that represents two or more component findings. The term “large nose” can serve as an example of a bundled term as the term comprises several distinct features: prominent nose; wide nasal ridge; prominent nasal tip; and broad nasal base. We have eliminated most bundled terms as they often include presumptions of pathogenesis or association, which may or may not be correct. Bundling is also problematic because it can obscure component abnormalities and if individuals are described using both the single bundled term and the component terms, it can lead to confusion. A number of terms have remained bundled, as we felt that the utility of the bundled term outweighed the potential pitfalls of bundling. If a term is considered to be bundled, this is mentioned in the definition and the individual components are indicated in the description.