Short stature (adult height usually less than 150
cm [59 inches] for males) caused by short limbs, large, disproportionate
head with frontal and occipital bossing, delayed suture closure and
prolonged persistence of fontanels, and lack of frontal sinuses. The midface
is hypoplastic with a prominent nose, grooved palate, and hypoplasia of the
mandibular angles, making these patients prone to obstructive sleep apnea.
The clavicles are affected by partial or complete aplasia. Progressive
acro-osteolytic dysplasia affects the distal phalanges of fingers and toes
with dystrophic, flattened, grooved, and brittle nails. Spondylolysis may
occur at the L4-L5 level and scoliosis is a common finding. Dentition
anomalies include delayed eruption and irregularities of the permanent
teeth, with or without partial anodontia. The brittle bone results in
fractures secondary to minimal trauma and the sometimes blue appearance of
the sclera may initially result in the diagnosis of osteogenesis imperfecta.
The intelligence is usually normal for the chronologic age but mild mental
retardation has been reported in some cases. Rarely, hyperostosis can lead
to the development of hematological complications (pancytopenia) similar to
those found in osteopetrosis. A low concentration of insulin-like growth
factor-1 has been reported for many patients suffering from pycnodysostosis.
Therapy with exogenous growth hormone showed improvement in the linear
growth. A significant abnormality of the hypothalamic-pituitary, thyroid,
or adrenal axis in these patients is generally not found.