guidebook. - Fanconi Anemia Research Fund

Chapter 5: Hand and Arm Differences in FA
109
absence of the radius (Type IV) is the most common
variant, and the hand develops a perpendicular relationship
with the forearm (Figure 9A and B). In FA children,
complete absence of the radius typically occurs in
conjunction with thumb absence.
Table 3: Classification of Radial Deficiency
Type X-ray findings Clinical Features
I
Short radius
II
Hypoplastic
III
Partial
absence
IV
Total
absence
Distal radial epiphysis
delayed in appearance.
Normal proximal radial
epiphysis. Mild shortening
of radius without ulna
bowing.
Distal and proximal
epiphysis present. Abnormal
growth in both epiphyses.
Ulna thickened, shortened,
and bowed.
Partial absence (distal,
middle, proximal) of radius.
Distal 1/3-2/3 absence most
common. Ulna thickened,
shortened, and bowed.
No radius present. Ulna
thickened, shortened, and
bowed.
Minor radial deviation
of the hand. Thumb
hypoplasia is the
prominent clinical
feature requiring
treatment.
Miniature radius.
Moderate radial
deviation of the hand.
Severe radial deviation
of the hand.
Most common type.
Severe radial deviation
of the hand.
Because ossification of the radius is delayed in radial deficiency, the
differentiation between total partial absence (Types III and IV) cannot
be established until approximately three years of age.
Centralization is indicated for Types II, III, and IV.
Adapted from Bayne and Klug.
A Type I deficiency is the mildest expression characterized
by mild radial shortening of the radius without
considerable bowing of the ulna. Although minor radial
deviation of the hand is apparent, considerable thumb
hypoplasia may be evident. A Type II deficiency presents
with a miniature radius with growth plate abnormalities
and moderate deviation of the wrist. A Type
III deficiency is partial absence of the radius, most