Most typical radiologic finding is platyspondyly
(flattening of the vertebral bodies), especially of the thoracic spine with
irregular endplates and wide intervertebral spaces. As in osteopetrosis,
vertebral bodies and the ribs show a diffusely increased density. Sclerosis
is found in the diaphyses and epiphyses of the long bones. The metaphyses
are splayed and osteoporotic as a result of cortical thinning, particularly
in the lower extremities. Metaphyseal widening extends progressively with
time. There is an increased risk of fractures even after trivial trauma.
Thickening and sclerosis of the skull base result in macrocephaly and
impingement of the basal foramina but particularly of the optic nerve canal,
causing optic atrophy with severe visual impairment or blindness, which
probably is the most important clinical finding. The electroretinogram and
visual evoked potentials confirm the gross loss of function of visual
pathways. Other radiologic findings include thickening and sclerosis of the
clavicles and scapulae and absent pneumatization of the paranasal sinuses
and the mastoids. Less commonly, hearing impairment or deafness may occur.
Growth hormone levels are abnormally low, resulting in progressive growth
retardation. Occasionally, hydrocephalus, hypertelorism, and micrognathia
with a high arched palate and excessive drooling are found. Progressive
mental retardation with loss of acquired milestones, sometimes associated
with seizures, is another important clinical finding. Dental hypoplasia with
delayed eruption of the first teeth and failure of the permanent teeth to
erupt are frequent findings. The teeth themselves are of diminished quality,
fall out prematurely, and show significant cavities. Macular, violet, or
dark rose areas of skin atrophy, which are caused by discrete fragmentation
and rarefaction of the elastic layer in the middle and deep sections of the
dermis, and flattening of the fingernails may occur.