Nanism caused by functional growth hormone deficiency.
Pituitary Dwarfism Type IV.
Exact incidence unknown. Less than 10 cases have been reported in
Autosomal recessive inheritance. Presumed
mutation is in the growth hormone gene on chromosome 17.
A structural abnormality of growth hormone causes
low levels of somatomedin, which results in delayed bone age and growth retardation.
Administration of exogenous growth hormone results in normal
somatomedin levels and a
significant increase in growth rate.
Phenotypical findings. Low levels of somatomedin.
Typical clinical findings in patients with
achondroplastic dwarfism may be absent in patients with Kowarski syndrome
who have been treated with exogenous growth hormone. Neurological findings in
achondroplastic dwarfs include foramen magnum stenosis and odontoid
hypoplasia causing spinal cord compression, central sleep apnea, and obstructive
hydrocephalus. Facial features are short maxilla, large tongue, and flat nose, which may
predispose to obstructive sleep apnea. Pulmonary hypertension and cor
pulmonale secondary to kyphoscoliosis and sleep apnea have been reported.
Although none of the typical
findings of achondroplasia are described in the referenced cases, any
patient with abnormal growth should be carefully evaluated for potential
difficult airway management, unstable cervical spine and/or spinal cord
compression, and potential adverse effects of delayed growth on the
respiratory and cardiovascular systems.
No specific considerations for isolated
short stature are required, especially if treated. If untreated, considerations may
include difficult laryngoscopy and avoidance of excessive airway
manipulation, which may further compress the spinal cord. If the patient is at
risk for apnea, judicious use of sedating medications and close
postoperative monitoring may be necessary. Respiratory and cardiovascular
compromise may increase complication rates and necessitate admission to an
intensive care unit postoperatively. Thick, lax skin can make vascular access challenging.
Other types of dwarfism,
especially the following:
Laron Syndrome: Features of this autosomal-recessive transmitted disorder
include severe dwarfism with sparse hair caused by primary (not acquired)
abnormally high concentrations of immunoreactive serum growth hormone and
insensitivity to exogenous growth hormone. Other features
include craniofacial abnormalities, relative obesity (mostly reflected by
excess of adipose tissue in the context of thin bones and diminished muscle
mass), and hypotonia. More than 250 cases reported
worldwide, but 65% of patients are of Semitic descent.
Kowarski AA, Schneider JJ, Ben-Galim E, et al: Growth failure with normal
serum RIA-GH and low somatomedin activity: Somatomedin restoration and
growth acceleration after exogenous GH. J Clin Endocrinol
Takahashi Y, Chihara K: Clinical significance and molecular mechanisms of bioinactive growth
hormone (review). Int J Mol Med
Valenta LJ, Sigel MB, Lesniak MA, et al: Pituitary dwarfism in a patient
with circulating abnormal growth hormone polymers. N Engl J Med