METATROPIC DWARFISM

¹ Fellow in Radiology, supported by U.S.P.H.S. Grant, ITI GMO 1538-03
² Professor of Radiology, School of Medicine, Emory University; and Radiologist, Henrietta Egleston Hospital for Children, Atlanta, Georgia

Maroteaux and associates have recently separated a clinical entity from the mixed group of short-limbed dwarfs, which they have designated as metatropic dwarfism. This disease can usually be recognized at birth, if a sufficient index of suspicion is present.

At birth, the trunk is long and narrow, and the chest is often described as cylindrical. Kyphoscoliosis and platyspondyly are present at this early date, but this is often not noticed clinically. The long tubular bones are short and thickened and have classical hyperplastic proximal metaphyses most noticeable at the lesser femoral trochanters. Bone age is variably delayed. The pelvis shows horizontal acetabula, shortened iliac wings and short, deep sacroiliac notches.

During growth, the tubular long bones lengthen more than would be expected in a true achondroplastic dwarf. The platyspondyly and kyphoscoliosis become progressively worse and the child clinically changes from what at first resembles an achondroplastic dwarf, to what is easily mistaken for spondyloepiphyseal dysplasia. The skeletal deformities usually progress despite orthopedic intervention.

Both the skull base and the interpedicular spaces are normal, which will help in differentiating this entity from achondroplasia at birth.

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