The patient may be clinically asymptomatic. The
patients are almost always tall as a result of increased limb length
(especially femur and tibia). The most frequent clinical feature is genu
valgum, which is usually mild but may predispose to fractures. The elbows
may not fully extend, the proximal humerus is abnormally wide, as are the
distal radius and ulna. The widening of the lower end of the femurs may be
palpable. There is a gross defect in metaphyseal modeling. Radiologic
examination of the spine may reveal platyspondyly, which could be attributed
to either the same defect in modeling seen in the metaphyses of the long
bones or to pathological fractures as a result of osteoporosis. Scoliosis
has been reported in some patients. The head is enlarged with diffuse
hyperostosis of the entire cranial vault, bony encroachment on the cranial
foramina (potentially resulting in nerve compression with visual and hearing
impairment/loss), absent or poorly pneumatized paranasal sinus,
significantly thickened bone in the area of the glabella with hypertelorism,
and often obstructed nasal breathing (breathing difficulties during upper
airway infections have been described). Inconsistently, the presence of
deciduous teeth is prolonged with marked cavities and prognathia may be
present. Intelligence and general health are normal.