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Mutations in the growth hormone releasing hormone receptor: a new form of dwarfism in humans.

We describe a recently identified new form of dwarfism due to isolated growth hormone (GH) deficiency, secondary to inactivating mutations in the GH-releasing hormone receptor (GHRHR) gene. The identical nonsense mutations in the extracellular domain of the GHRHR (E72X or E50X, depending on whether the signal peptide is included in the numbering) has been independently described in three families residing on or originating from the Indian subcontinent (Pakistan, the Bombay region, and Delft near Sri Lanka). Another inactivating mutation, involving the donor splice site of intron 1, has been identified in a population in north-eastern Brazil. Genetic transmission is autosomal recessive; the gene is located on the short arm of chromosome 7. Affected subjects have severe isolated GH deficiency and postnatal growth failure, with a mean adult height of 130 cm for men and 114 cm for women (7-8 standard deviations below the norm). Dwarfism is proportional; a characteristic feature is relative microcephaly, which results in a 'miniaturized adult', eumorphic aspect. Bone age and puberty are delayed, but fertility appears normal. This new syndrome corresponds to the human homologue of the previously identified 'little mouse'.

Adult↗

Propofol pharmacokinetics in a dwarfism patient.

Pharmacokinetic information is important to control anesthetic depth. However, there are few available pharmacokinetic data of propofol in dwarfism patients. We anesthetized a dwarfism patient who underwent spinal decompression, and investigated the pharmacokinetics of propofol. The patient was a 40-year-old man suffering from muscle weakness and numbness in the arms. The operation consisted of two stages; anterior approach in the supine position and posterior approach in the prone position. We also obtained arterial blood for pharmacokinetic analysis. Distribution volume at steady-state and clearance in the supine position was 180 and 0.92 l min- 1, respectively, and in the prone position 127 and 0.74 l min- 1, respectively, in spite of a continuous infusion of dopamine. The data in the supine position were well predicted by Gepts' parameters (used in Diprifusor Zeneca Ltd, Cheshire, UK), which means the target-controlled infusion (TCI) technique can be available in the supine position, while attention is necessary to avoid overdosing when a patient is placed in the prone position.

Adult↗

Dwarfism in an adolescent from the Italian late Upper Palaeolithic.

There have been numerous reports of pathological conditions in the hominid fossils, but these have only involved trauma or age-related deterioration in the health of otherwise normal individuals. Here we describe a skeleton of a young male from Riparo del Romito in Calabria, dated to the Epi-Gravettian of southern Italy. The preserved skeletal elements show that this individual (Romito 2) had the skull and long-bone morphology consistent with a mesomelic form of dwarfism, most probably the autosomal recessive disorder acromesomelic dysplasia. Generally recognized at birth, persons with acromesomelic dysplasia usually have normal intelligence and are free of serious medical problems. However, growth deficiency is severe (adult height typically is 110-120 cm) and mobility at the elbows is restricted. These physical impairments would have greatly interfered with the individual's participation in subsistence activities and would have been a substantial handicap in a nomadic hunting and gathering group. Thus, besides being the earliest known case of dwarfism in the human record, this skeleton provides evidence of tolerance of, and care for, a severely deformed individual in the Palaeolithic.

Adolescent↗

The bovine fibroblast growth factor receptor 3 (FGFR3) gene is not the locus responsible for bovine chondrodysplastic dwarfism in Japanese brown cattle.

Fibroblast growth factor receptor 3 (FGFR3) is one of the four distinct membrane-spanning tyrosine kinase receptors for fibroblast growth factors. The FGFR3 is a negative regulator of endochondral ossification and mutations in the FGFR3 gene have been found in patients of human hereditary diseases with chondrodysplastic phenotypes. Recently, we mapped the locus responsible for hereditary chondrodysplastic dwarfism in Japanese brown cattle to the distal region of bovine chromosome 6 close to the FGFR3 gene, suggesting that FGFR3 was a positional candidate gene for this disorder. In the present study, we isolated complementary DNA (cDNA) clones containing the entire coding region of the bovine FGFR3 gene. Comparison of the nucleotide sequence between affected and normal animals revealed no disease-specific differences in the deduced amino acid sequences. We further refined the localization of FGFR3 by radiation hybrid mapping, which is distinct from that of the disease locus. Therefore we conclude that bovine chondrodysplastic dwarfism in Japanese brown cattle is not caused by mutation in the FGFR3 gene.

Animals↗

[Prenatal diagnosis of thanatophoric dwarfism with a cloverleaf skull--ultrasonographic findings, humane genetic aspects].

The ultrasonographic criteria for the prenatal diagnosis of thanatophore dwarfism with clover leaf skull are described. Facultative morbid anatomical peculiarities are described. Because of the prenatal findings the pregnancy was terminated by Caesarean Section at 30 weeks gestation in our case. Following the death of the infant the diagnosis was confirmed by radiological investigations and by autopsy. The ultrasonographic differential diagnosis from other types of dwarfism is discussed. The human genetic aspects are discussed with emphasis on the counselling regarding further pregnancies.

Abnormalities, Multiple↗

Dwarfism and early death in mice lacking C-type natriuretic peptide.

Longitudinal bone growth is determined by endochondral ossification that occurs as chondrocytes in the cartilaginous growth plate undergo proliferation, hypertrophy, cell death, and osteoblastic replacement. The natriuretic peptide family consists of three structurally related endogenous ligands, atrial, brain, and C-type natriuretic peptides (ANP, BNP, and CNP), and is thought to be involved in a variety of homeostatic processes. To investigate the physiological significance of CNP in vivo, we generated mice with targeted disruption of CNP (Nppc(-/-) mice). The Nppc(-/-) mice show severe dwarfism as a result of impaired endochondral ossification. They are all viable perinatally, but less than half can survive during postnatal development. The skeletal phenotypes are histologically similar to those seen in patients with achondroplasia, the most common genetic form of human dwarfism. Targeted expression of CNP in the growth plate chondrocytes can rescue the skeletal defect of Nppc(-/-) mice and allow their prolonged survival. This study demonstrates that CNP acts locally as a positive regulator of endochondral ossification in vivo and suggests its pathophysiological and therapeutic implication in some forms of skeletal dysplasia.

Animals↗

Positional cloning of the gene LIMBIN responsible for bovine chondrodysplastic dwarfism.

Chondrodysplastic dwarfism in Japanese brown cattle is an autosomal recessive disorder characterized by short limbs. Previously, we mapped the locus responsible for the disease on the distal end of bovine chromosome 6. Here, we narrowed the critical region to approximately 2 cM by using linkage analysis, constructed a BAC and YAC contig covering this region, and identified a gene, LIMBIN (LBN), that possessed disease-specific mutations in the affected calves. One mutation was a single nucleotide substitution leading to an activation of a cryptic splicing donor site and the other was a one-base deletion resulting in a frameshift mutation. Strong expression of the Lbn gene was observed in limb buds of developing mouse embryos and in proliferating chondrocytes and bone-forming osteoblasts in long bones. These findings indicate that LBN is responsible for bovine chondrodysplastic dwarfism and has a critical role in a skeletal development.

Amino Acid Sequence↗

Absence of serum growth hormone binding protein in patients with growth hormone receptor deficiency (Laron dwarfism).

It has recently been recognized that human serum contains a protein that specifically binds human growth hormone (hGH). This protein has the same restricted specificity for hGH as the membrane-bound GH receptor. To determine whether the GH-binding protein is a derivative of, or otherwise related to, the GH receptor, we have examined the serum of three patients with Laron-type dwarfism, a condition in which GH refractoriness has been attributed to a defect in the GH receptor. The binding of 125I-labeled hGH incubated with serum has been measured after gel filtration of the serum through an Ultrogel AcA 44 minicolumn. Nonspecific binding was determined when 125I-hGH was incubated with serum in the presence of an excess of GH. Results are expressed as percent of specifically bound 125I-hGH and as specific binding relative to that of a reference serum after correction is made for endogenous GH. The mean +/- SEM of specific binding of sera from eight normal adults (26-46 years of age) was 21.6 +/- 0.45%, and the relative specific binding was 101.1 +/- 8.6%. Sera from 11 normal children had lower specific binding of 12.5 +/- 1.95% and relative specific binding of 56.6 +/- 9.1%. Sera from three children with Laron-type dwarfism lacked any demonstrable GH binding, whereas sera from 10 other children with other types of nonpituitary short stature had normal relative specific binding. We suggest that the serum GH-binding protein is a soluble derivative of the GH receptor. Measurement of the serum GH-binding protein may permit recognition of other abnormalities of the GH receptor.

Adolescent↗

Gene disruption of Spred-2 causes dwarfism.

The impact of the fibroblast growth factor receptor 3 (FGFR3)-mediated signaling pathway on bone growth has been demonstrated by various genetic approaches. Overexpression of fibroblast growth factors (FGFs), several gain-of-function mutations in the FGFR3, and constitutive activation of mitogen-activated protein kinase (MAPK) kinase (MEK1) in chondrocytes have been shown to cause dwarfism in mice by activation of the MAPK signaling pathway. To investigate the previously reported inhibitory role of Spred in the FGFR3/MAPK pathway, we generated mice with a trapped Spred-2 gene. Here we show that lack of functional Spred-2 protein in mice caused a dwarf phenotype, similar to achondroplasia, the most common form of human dwarfism. Spred-2(-/-) mice showed reduced growth and body weight, they had a shorter tibia length, and showed narrower growth plates as compared with wild-type mice. We detected promoter activity and protein expression of Spred-2 in chondrocytes, suggesting an important function of Spred-2 in chondrocytes and bone development. Stimulation of chondrocytes with different FGF concentrations showed earlier and augmented ERK phosphorylation in Spred-2(-/-) chondrocytes in comparison to Spred-2(+/+) chondrocytes. Our observations suggest a model in which loss of Spred-2 inhibits bone growth by inhibiting chondrocyte differentiation through up-regulation of the MAPK signaling pathway.

Animals↗

Inherited ateliotic dwarfism in mice. Characteristics of the mutation, little, on chromosome 6.

A new autosomal recessive mutation in the mouse, little (lit), has been shown to be located on Chromosome 6. The mutation in the homozygous state causes ateliotic dwarfism that is first detected at 15 days of age by decreased body weight. Long bone lengths are significantly reduced. Skull width, however, is not affected. Female little mice are fully fertile; they may lose their first litters. Although most of the little males sire one or two litters, they rarely sire a third litter. Analysis of pituitary extracts electrophoresed on acrylamide gels reveal a significant reduction of the two anterior pituitary hormones, GH and PRL, in both male and female little mice. Because the little mouse shares a number of similarities with the human ateliotic dwarfism, isolated growth hormones deficiency type I, it may be a useful animal model for this inherited human growth disorder.

Animals↗

Mesomelic dwarfism in pseudoachondroplasia.

Pseudoachondroplasia (PSACH) is associated with mutations in the cartilage oligomeric matrix protein (COMP) gene and the clinical characteristics include short stature, deformities of the extremities involving the epiphyses and metaphyses, early onset arthritis, and ligament laxity. PSACH has been considered a rhizomelic form of dwarfism. So far no previous report has described mesomelic shortening of the limbs in PSACH. We reviewed nine patients with a diagnosis of PSACH based on clinical and radiographic examination and mutation analysis of the COMP gene. The mean height in the adults was 116 cm. All patients showed mesomelic dwarfism. The average ratios of radial length to humeral length and tibial length to femoral length were 0.62 and 0.63, respectively. The tibia and the radius showed more severe bony deformity than the femur and humerus. The degree of short stature was related to the site of the mutation in the COMP gene, but there was no correlation between bony deformity and height or gene mutation.

Achondroplasia↗

Dwarfism in Dexter cattle is not caused by the mutations in FGFR3 responsible for achondroplasia in humans.

Dexter cattle carry a genetic defect causing a dwarf phenotype in the heterozygotes (Dx+/-), while homozygotes (Dx+/+) are stillborn with extreme shortening of limbs and gross craniofacial defects and are described as 'bulldog' calves. The heterozygous phenotype has been likened to achondroplastic dwarfism in humans (ACH), which has recently been shown to be the result of mutations in the transmembrane region of the fibroblast growth factor receptor 3 (FGFR3) gene. We have sequenced the transmembrane region of bovine FGFR3 from normal Dexter cattle (Dx-/-) and bulldog calves (Dx+/+). The sequence from both is identical and therefore excludes mutations in the trans-membrane region of FGFR3 as the cause of Dexter dwarfism.

Achondroplasia↗

Biochemical and hormonal changes induced by one week of administration of rIGF-I to patients with Laron type dwarfism.

OBJECTIVE: The purpose of this investigation was to evaluate the effectiveness of short-term administration of recombinant biosynthetic IGF-I on patients with an hereditary inability to generate this hormone. DESIGN AND PATIENTS: Ten patients with Laron type dwarfism (LTD) (4 males, six females) aged 3 1/2 to 37 3/4 years were submitted to seven daily s.c. injections of recombinant IGF-I in doses of 120 or 150 micrograms/kg/day. MEASUREMENTS: Blood samples were drawn before, after three and seven injections, and one week after stopping the trial. RESULTS: The main biochemical and hormonal changes registered were (mean +/- SD): a marked rise in serum type III procollagen (PIIINP) from 4.2 +/- 0.9 to 7.3 +/- 2 micrograms/l (P less than 0.0003) and decrease in the following blood components: plasma hGH from 32.51 +/- 43.77 to 4.02 +/- 2.48 mU/l (P less than 0.001), serum cholesterol from 5.9 +/- 1 to 5.7 +/- 0.8 mmol/l (P less than 0.04), serum SGOT from 28.9 +/- 11.6 to 15.5 +/- 7.6 U/l (P less than 0.01) and serum LDH from 286 +/- 88 to 222 +/- 37 U/l (P less than 0.0005). The response of plasma insulin was variable, decreasing in seven of ten and increasing in three. Some of these effects were transitory, and were found after 3 days therapy but afterwards decreased (insulin, cholesterol and liver tests), others persisted throughout the whole treatment period (hGH, PIINP). CONCLUSIONS: IGF-I mimics the biochemical and hormonal changes described after administration of hGH. The administration of IGF-I in patients with Laron type dwarfism is devoid of side-effects and warrants assessment in long-term studies.

Adolescent↗

Dominant mesomelic dwarfism of the hypoplastic tibia, radius type.

A new type of mesomelic dwarfism in two male siblings and their father is presented. The responsible mutant gene manifests itself phenotypically as a severe dysostosis of the tibia with shortening, bowing and pseudarthrosis and as a mild dysostosis of the radius. The fibulae and ulnae are secondarily affected, but the rest of the skeleton is normal. The disorder has an autosomal dominant mode of inheritance. It can be differentiated rather easily from the already known forms of mesomelic dwarfism.

Chromosome Aberrations↗

Microcephalic osteodysplastic dwarfism (type II-like) in siblings.

We report about two sibs showing a common pattern of birth defects, with a pedigree suggestive of autosomal recessive heredity. The main features are intrauterine growth failure with very low birthweight; disproportionate dwarfism with predominantly distal shortening of limbs; small cubitally inclined clenched hands; microcephaly with Seckel-like facies and delayed psychomotor development. X-ray findings include metaphyseal flare, V-shaped femoral metaphyses and bowing of forearms. Primordial microcephalic osteodysplastic dwarfism Type II is discussed. Metabolic and nutritional data are presented and discussed.

Diseases in Twins↗

Reversible somatotropin deficiency (psychosocial dwarfism) presenting as conduct disorder and growth hormone deficiency.

The syndrome of reversible somatotropin deficiency (psychosocial dwarfism) is characterized by environment-related impairment of stature and mental growth and growth-hormone secretion. The syndrome is well illustrated by this case report of an eight-year-old boy with psychosocial dwarfism since the third year of life. It was undetected for four years, despite his having been in regular contact with a number of health workers. After he was removed from the deleterious environment, both his growth and behaviour improved markedly, and at follow-up he had maintained this progress.

Child↗

Hypochondroplastic dwarfism in the Irish setter.

Two test matings in the irish setter were performed, and genetic, clinical, morphometric, radiographic, bone histological and plasma and urine biochemical features of dwarfism were studied. All offspring were phenotypically normal at birth and weaning, but at the age of 2.5 to 4 months the longitudinal growth of the spine and leg bones was retarded in the dwarfs compared with the normal littermates. Most dwarfs performed well, even in the field. Radiographic and histological evaluations revealed a hypochondroplasia. A morphometric diagnostic method for Irish setter dwarfism was developed. A single autosomal recessive mode of inheritance was verified.

Achondroplasia↗

Use of proligestone in the management of three German shepherd dogs with pituitary dwarfism.

Three German shepherd dogs were diagnosed with pituitary dwarfism and subsequently treated with proligestone. Treatment resulted in development of an adult hair coat, increased bodyweight and elevated insulin-like growth factor-1 concentration. Two dogs received thyroid supplementation during proligestone therapy. Adverse effects (cystic endometrial hyperplasia and acromegaly) were reported in two cases. No side effects were reported in the remaining case. This is the first report of the use of proligestone in the management of pituitary dwarfism.

Acromegaly↗