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Nanism caused by functional growth hormone deficiency.

Pituitary Dwarfism Type IV.

Exact incidence unknown. Less than 10 cases have been reported in the literature.

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 47:461, 1978.  [PubMed: 263308]
Takahashi Y, Chihara K: Clinical significance and molecular mechanisms of bioinactive growth hormone (review). Int J Mol Med 2:287, 1998.  [PubMed: 9855700]
Valenta LJ, Sigel MB, Lesniak MA, et al: Pituitary dwarfism in a patient with circulating abnormal growth hormone polymers. N Engl J Med 312:214, 1985.  [PubMed: 3965948]

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