Dwarfism syndromes are complex, heterogeneous, and generally rare. Most radiologists are familiar with achondroplasia, the most common short-limbed dwarfism syndrome, but there are a variety of other syndromes within this category, and three other types of limb shortening. In fact, dwarfism as an entity is a type of skeletal dysplasia - a term used to refer to syndromes with abnormal bone growth and development. The term dwarf is somewhat ambiguous, but generally refers to a condition with shortening of a limb or the spine such that the pattern is recognized as a syndrome and that the affected region is generally shorter than 97 % of children of the same age. It should be noted, however, that children with very short stature but no limb shortening may simply be normal or may have a metabolic condition such as malnutrition.  

Several terms are used when describing which bone within a limb is most shortened:

Rhizomelic: proximal shortening (humerus or femur)

Mesomelic: middle shortening (tibia/fibula or radius/ulna)

Acromelic: distal shortening (hand)

Micromelic: entire limb shortened

How then, to approach the dwarfism syndromes? One scheme is presented below. On the right, the classification system is described. On the left, examples within these categories are listed. Please click on one of these to further investigate.

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