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Hand and finger malformations represent a challenging area of clinical genetics from the standpoint of understanding the classification as well as in understanding the genetic etiologies, which are often due to single gene mutations. The majority of familial types however are not yet associated with specific genes. In addition, there is terrific variation in expression between affected family members. Another challenge in studying hand anomalies is that the literature will often refer to certain malformation types (e.g., brachydactyly type E) without defining what this type is. If the reader is not familiar with a visual image of the malformation, then learning may be hindered. Accordingly, the purpose of these diagrams is to present images of the common polydactyly, syndactyly and brachydactly malformations that have been described.

The Hand Syndactylies: Common Types

Polydactylies, Classification for thumb (preaxial) and little finger (postaxial) types.

These diagrams illustrate the main types of polydactyly. These malformations are usually observed in otherwise normal children, and often have an autosomal dominant pattern of inheritance.

Brachydactyly Classification Types

Diagramed below is the classification system used to describe hand anomalies associated with shortening of the fingers. Most are autosomal dominant. For some, genes have been identified but genetic heterogeneity is present in all, as well as variable expression. Darkened areas show the main bone findings. For some types, such as in A5 and B, there is absence of bones (middle phalanges) so that no "dark" areas are indicated.