Skeletal dysplasia, growth hormone treatment and body proportion: comparison with other syndromic and non-syndromic short children

What the pediatric endocrinologist needs to know about skeletal dysplasia, a primer

Children with skeletal dysplasia are frequently referred to pediatric endocrinologists due to short stature. These children may present with disproportionate growth or medical histories that point to a skeletal dysplasia. This primer will discuss when to be concerned about skeletal dysplasia, the initial steps in evaluation for a skeletal dysplasia, and new therapies that are either recently approved or in development.

New insight into the importance of formulation variables on parenteral growth hormone preparations: potential effect on the injection-site pain

Reducing injection-site pain (ISP) in patients with chronic conditions such as growth hormone deficiency is a valuable strategy to improve patient compliance and therapeutic efficiency. Thus understanding different aspects of pain induction following subcutaneous injection of biotherapeutics and identifying the responsible factors are vital. Here we have discussed the effects of formulation's viscosity, concentration, osmolality, buffering agents, pH, and temperature as well as injection volume, dosing frequency, and different excipients on ISP following subcutaneous injection of commercially available recombinant human growth hormone products. Our literature review found limited available data on the effects of different components of parenteral rhGH products on ISP. This may be due to high cost associated with conducting various clinical trials to assess each excipient in the formulation or to determine the complex interactions of different components and its impact on ISP. Recently, conducting molecular dynamics simulation studies before formulation design has been recommended as an alternative and less-expensive approach. On the other hand, the observed inconsistencies in the available data is mainly due to different pain measurement approaches used in each study. Moreover, it is difficult to translate data obtained from animal studies to human subjects. Despite all these limitations, our investigation showed that components of parenteral rhGH products can significantly contribute to ISP. We suggest further investigation is required for development of long acting, buffer-free, preservative-free formulations. Besides, various excipients are currently being investigated for reducing ISP which can be used as alternatives for common buffers, surfactants or preservatives in designing future rhGH formulations.

Identification of an Autosomal Dominant Mutation in the COL2A1 Gene Leading to Spondyloepiphyseal Dysplasia Congenita in a Greek Family

A boy and his father with severe short stature, progressively evolving body asymmetry, and skeletal abnormalities are presented. A next-generation sequencing exome study was performed, and the patient was found heterozygous for the c.1609G>A (p.Gly537Ser) mutation in the COL2A1 gene. This mutation is considered a pathogenic variant and has been previously registered in the Human Gene Mutation Database (HGMD) in association with spondyloepiphyseal dysplasia (accession: CM052184). It has been described in a patient as a sporadic case and resulted in a severe phenotype. Segregation studies, in order to determine the inheritance pattern, identified the same mutation in our patient's father. The variant was transmitted in an autosomal dominant pattern. In conclusion, we describe a patient with hereditary spondyloepiphyseal dysplasia congenita, caused by a c.1609G_A (p.Gly537Ser) mutation in the COL2A1 gene, which resulted in a milder phenotype.

Evaluation of Efficacy of Long-term Growth Hormone Therapy in Patients with Hypochondroplasia

Hypochondroplasia is a cause of disproportionate short stature and characterized by minor clinical manifestations. The aim of this study was to evaluate the efficacy of long-term growth hormone (GH) therapy in hypochondroplastic cases with inadequate response to GH stimulation tests. In this study, six patients who had a height standard deviation score of -3.43 before the treatment and a mean age of 7.42 years and who had received GH treatment at a dose of 0.2 mg/kg/week for a mean period of 4.45 years were evaluated. A good response was found in the first year of treatment, but this increase was not found to be sufficient for the patients to achieve an adequate final height.

The Clinical Cases of Geleophysic Dysplasia: One Gene, Different Phenotypes

Background

Geleophysic dysplasia is a rare multisystem disorder that principally affects the bones, joints, heart, and skin. This condition is inherited either in an autosomal dominant pattern due to FBN1 mutations or in an autosomal recessive pattern due to ADAMTSL2 mutations. Two patients with unaffected parents from unrelated families presented to their endocrinologist with severe short stature, resistant to growth hormone treatment. Routine endocrine tests did not reveal an underlying etiology. Exome sequencing was performed in each family. Our two patients, harboring de novo heterozygous FBN1 mutations p.Tyr1696Asp and p.Cys1748Ser, had common clinical symptoms such as severe short stature, characteristic facial features, short hands and feet, and limitation of joint movement. However, one patient had severe cardiac involvement whereas the other patient had tracheal stenosis requiring tracheostomy placement.

Conclusions

Patients with severe dwarfism, skeletal anomalies, and other specific syndromic features (e.g., tracheal stenosis and cardiac valvulopathy) should undergo genetic testing to exclude acromelic dysplasia syndromes.

Body proportions in children with Kabuki syndrome

Facial characteristics, short stature, and skeletal anomalies have been described for the clinical diagnosis of Kabuki Syndrome (KS) in children. However, no studies have investigated body proportions in KS. Knowledge of body proportions in KS may contribute to better insight into the growth pattern and characterization of this genetic disorder. Therefore we compared body proportions of children with KS to normally proportioned controls to investigate if atypical body proportions are part of this genetic disorder. This study was designed and conducted within the setting of the Maastricht University Medical Centre (MUMC+), the official Dutch expert center for Kabuki syndrome. We conducted a cross-sectional study in 32 children (11 children with KS and 21 controls). Body proportions were determined by means of photogrammetric anthropometry, measurements based on digital photography. Body proportions, quantified as body ratios, differ significantly in children with KS from normally proportioned children. Children with KS have larger heads and longer arms proportional to their trunks and have been found to have longer upper arms proportional to their tibia length and feet. Based on deviations in body proportions it was shown possible to discern children with KS from normally proportioned controls.

Efficacy and safety of growth hormone treatment in children with hypochondroplasia: comparison with an historical cohort

BACKGROUND/AIMS

Hypochondroplasia (HCH) is a skeletal dysplasia characterized by disproportionate short stature. The aims of the study are to evaluate efficacy and safety of recombinant human growth hormone (r-hGH) therapy in HCH children, when compared with a historical cohort of untreated HCH children.

METHODS

Nineteen HCH patients with an initial height standard deviation score (SDS) ≤-2 and a mean age of 9.3 ± 3.1 years were treated with a mean r-hGH dose of 0.053 mg/kg/day over 3 years. Growth charts were derived from the historical cohort (n = 40).

RESULTS

Height gain in the treated population was +0.62 ± 0.81 SDS greater than in the general population, and +1.39 ± 0.9 SDS greater than in the historical untreated HCH cohort (mean gain of 7.4 ± 6.6 cm gain). A negative correlation between height gain and age at treatment initiation was reported (p = 0.04). There was no significant difference in response between patients with fibroblast growth factor receptor 3 mutations and those without. No treatment-related serious adverse events were reported.

CONCLUSIONS

r-hGH treatment is well tolerated and effective in improving growth in HCH patients, particularly when started early. The treatment effect varies greatly and must be evaluated for each patient during treatment to determine the value of continued therapy.

Growth and development. Bone dysplasia--a frequent cause of short stature in children

In children presenting with short stature, physicians often limit themselves to descriptive diagnoses such as idiopathic short stature or small for gestational age. Flechtner and colleagues now report a high frequency of bone dysplasias in these children, raising questions about the process of diagnosing short stature.

Hypochondroplasia in a child with 1620C>G (Asn540Lys) mutation in FGFR3

Hypochondroplasia (HCP) is an autosomal dominant skeletal dysplasia characterized by short extremities, short stature and lumbar lordosis, usually exhibiting a phenotype similar to but milder than achondroplasia (ACP). Fibroblast growth factor receptor 3 gene (FGFR3) mutations in the germline are well-known causes of skeletal syndromes. FGFR3 is a negative regulator of bone growth and all mutations in FGFR3 are gain-of-function mutations that lead to skeletal dysplasias. We report a child who presented with short stature, a relatively long trunk, short legs, short arm span, radiographic evidence of HCP and mild mental retardation. Genetic analysis revealed a heterozygous 1620C>G (Asn540Lys) mutation in FGFR3. To our knowledge, ours is the first case report of HCP with a heterozygous 1620C>G (Asn540Lys) mutation in Turkey.

Growth and growth hormone therapy in subjects with mulibrey nanism

OBJECTIVES

Mulibrey nanism is a monogenic disorder with prenatal-onset growth restriction, mild dysmorphic features, and a strong tendency for insulin resistance but no major neurologic handicap. Growth hormone therapy has been shown to promote short-term growth in children born small for gestational age, but the experience with long-term therapy is insufficient. Growth in patients with mulibrey nanism has not been analyzed previously in detail.

METHODS

We evaluated the natural growth pattern and long-term impact of growth hormone treatment in the largest cohort of subjects with mulibrey nanism to date. The study included 72 living subjects followed up to 30 years. Thirty (18 female) were treated with recombinant human growth hormone for a median period of 5.7 years. Patients were reviewed at baseline and every 6 to 12 months during the therapy. Evaluation included assessment of height, weight, and pubertal status and laboratory analyses. Glucose metabolism was evaluated by oral glucose-tolerance test.

RESULTS

The patients were born small for gestational age with immature craniofacial features. They experienced a continuous deceleration in height (median decrement of 1.1 SDS) and weight for height (median reduction of 17%) in infancy followed by an incomplete catch-up growth lasting up to school age. The final adult height averaged 136 cm in girls and 150 cm in boys. Growth hormone treatment improved the prepubertal growth but had only little impact on adult height (+5 cm). The treated subjects showed earlier bone maturation and growth arrest but not a significant increase in insulin resistance. On the contrary, the subjects who were treated with growth hormone were slimmer and had less metabolic syndrome as young adults.

CONCLUSIONS

The patients with mulibrey nanism showed a distinct postnatal growth pattern. The growth hormone treatment was safe and induced a good short-term effect, but the impact on the adult height remained modest.

Evolutionary comparison provides evidence for pathogenicity of RMRP mutations

Cartilage-hair hypoplasia (CHH) is a pleiotropic disease caused by recessive mutations in the RMRP gene that result in a wide spectrum of manifestations including short stature, sparse hair, metaphyseal dysplasia, anemia, immune deficiency, and increased incidence of cancer. Molecular diagnosis of CHH has implications for management, prognosis, follow-up, and genetic counseling of affected patients and their families. We report 20 novel mutations in 36 patients with CHH and describe the associated phenotypic spectrum. Given the high mutational heterogeneity (62 mutations reported to date), the high frequency of variations in the region (eight single nucleotide polymorphisms in and around RMRP), and the fact that RMRP is not translated into protein, prediction of mutation pathogenicity is difficult. We addressed this issue by a comparative genomic approach and aligned the genomic sequences of RMRP gene in the entire class of mammals. We found that putative pathogenic mutations are located in highly conserved nucleotides, whereas polymorphisms are located in non-conserved positions. We conclude that the abundance of variations in this small gene is remarkable and at odds with its high conservation through species; it is unclear whether these variations are caused by a high local mutation rate, a failure of repair mechanisms, or a relaxed selective pressure. The marked diversity of mutations in RMRP and the low homozygosity rate in our patient population indicate that CHH is more common than previously estimated, but may go unrecognized because of its variable clinical presentation. Thus, RMRP molecular testing may be indicated in individuals with isolated metaphyseal dysplasia, anemia, or immune dysregulation.

Growth hormone (GH): usage and abuse

Growth hormone is essential for body growth but it also modulates metabolic pathways as well as neural, reproductive, immune, cardiovascular, and pulmonary functions. Numerous beneficial effects of growth hormone have led to its expanded therapeutic use in both children and adults. There are several officially approved applications of human growth hormone and many more proposed applications that resulted from huge number of clinical studies on GH therapy. Growth hormone abuse includes improper or excessive use. Over the last decade GH has become one of the most commonly abused drugs in sport due to the fact that its administration is currently undetectable. Enormous doses that are injected and frequent simultaneous abuse of other substances such as other anabolic steroids (testosterone) lead to frequent side effects that may be fatal. In spite of numerous beneficial effects of growth hormone the true physiological impact of GH replacement therapy on various metabolic parameters may be confounded by the dose and route of administration of GH so accurate physicians' monitoring during GH therapy is needed.