guidebook. - Fanconi Anemia Research Fund

Chapter 5: Hand and Arm Differences in FA
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Anomalies (Differences)
The most common abnormalities in FA children affect
the thumb and may or may not include the radial border
of the forearm. The thumb may be smaller (hypoplasia)
or absent. Similarly, the radius may be shortened (hypoplasia
or deficiency) or absent.
Figures 1A and 1B: Six-year-old child with left thumb hypoplasia.
A Type II deficiency is apparent with thumb-index web space narrowing
and absence of the thenar muscles.