Cenani-Lenz syndactyly syndrome - a case report of a family with isolated syndactyly

The burden of hospital admissions for skeletal dysplasias in Sri Lanka: a population-based study

BACKGROUND

Skeletal dysplasias are a diverse group of rare disorders in the chondro-osseous tissue that can have a significant impact on patient's functionality. The worldwide prevalence of skeletal dysplasias at birth is approximately 1:5000 births. To date, disease burden and trends of skeletal dysplasias in the Sri Lankan population have not been described in any epidemiological study. Our aim was to evaluate the burden and the current trends in hospital admissions for skeletal dysplasias in the Sri Lankan population. A retrospective evaluation of hospital admissions for skeletal dysplasia during 2017-2020 was performed using population-based data from the eIMMR database which covers government hospitals in the entire country. The trends in hospital admissions for skeletal dysplasias by calendar year, age, and types of skeletal dysplasia were described using appropriate summary statistics.

RESULTS

Respective crude admission rates of skeletal dysplasias in the years 2017, 2018, 2019 and 2020 were 5.2, 8.1, 8.0, and 6.5 per million population. A female predominance (1.4:1) was noted during the studied period. Of all reported cases the majority (n = 268; 44.2%) were children less than 4 years. Each year, 0-4 years age group represented 40-47% of the total hospital admissions. More than half of the cases were reported from Colombo (28.1%) and Kandy (25.4%) districts combined. 60% of cases were diagnosed as osteogenesis imperfecta (OI). Rising trends were observed in the hospital admissions for osteogenesis imperfecta, achondroplasia and osteopetrosis, while other skeletal dysplasia types collectively showed a relatively stable trend.

CONCLUSION

This preliminary study revealed a female predominance of skeletal dysplasias and a relatively high admission rate of osteogenesis imperfecta in the Sri Lankan population. A distinct trend was not visible in the studied years probably due to the impact on hospital services due to COVID- Pandemic. Future research on the healthcare burden on families affected by skeletal dysplasia is required to better understand the overall cost of care and identify therapies that reduce admission rates. This study highlights the value of analysing population-based data on rare diseases to improve healthcare in low-resource countries.

Foot Oligodactyly as the Main Dysplasia in Children

Introduction Foot oligodactyly is usually associated with fibular insufficiency or cleft foot syndrome. A foot with a reduced number of rays may occasionally have an isolated dysplasia. Methods We reviewed the clinical notes and X-rays of six children with oligodactyly, having a normal development of the tibia and fibula. Clinical evaluation recorded the plantigrade or deviated foot, appropriate shoe wear, and aesthetic presentation of barefoot children. Radiological examination revealed missing or hypoplastic bones in the foot, the presence of other deformities, and leg length discrepancy (LLD) of the affected limb. Results On clinical evaluation, all children except one had a plantigrade foot with normal shoe wear; the lesion was not spotted in three of them unless informed of the presence of the dysplasia. Radiological examination in four of them revealed the absence or hypoplasia of the navicular, with a normal shape of the first metatarsal. Calcaneocuboid joints were normal in five of them; LLD was the main problem in three children. The girl with bilateral oligodactyly presented as a normal child. Conclusion Oligodactyly may present as an isolated dysplasia. LLD in these patients, which is less severe than in children with fibular or tibial insufficiency, is the main issue that requires surgical management in later life. Prenatal diagnosis of oligodactyly as an isolated dysplasia is an important feature for appropriate counseling of parents.

Recent Advances in Syndactyly: Basis, Current Status and Future Perspectives

A comprehensive summary of recent knowledge in syndactyly (SD) is important for understanding the genetic etiology of SD and disease management. Thus, this review article provides background information on SD, as well as insights into phenotypic and genetic heterogeneity, newly identified gene mutations in various SD types, the role of HOXD13 in limb deformities, and recently introduced modern surgical techniques for SD. This article also proposes a procedure for genetic analysis to obtain a clearer genotype-phenotype correlation for SD in the future. We briefly describe the classification of non-syndromic SD based on variable phenotypes to explain different phenotypic features and mutations in the various genes responsible for the pathogenesis of different types of SD. We describe how different types of mutation in HOXD13 cause various types of SD, and how a mutation in HOXD13 could affect its interaction with other genes, which may be one of the reasons behind the differential phenotypes and incomplete penetrance. Furthermore, we also discuss some recently introduced modern surgical techniques, such as free skin grafting, improved flap techniques, and dermal fat grafting in combination with the Z-method incision, which have been successfully practiced clinically with no post-operative complications.

Wnt Pathway Extracellular Components and Their Essential Roles in Bone Homeostasis

The Wnt pathway is involved in several processes essential for bone development and homeostasis. For proper functioning, the Wnt pathway is tightly regulated by numerous extracellular elements that act by both activating and inhibiting the pathway at different moments. This review aims to describe, summarize and update the findings regarding the extracellular modulators of the Wnt pathway, including co-receptors, ligands and inhibitors, in relation to bone homeostasis, with an emphasis on the animal models generated, the diseases associated with each gene and the bone processes in which each member is involved. The precise knowledge of all these elements will help us to identify possible targets that can be used as a therapeutic target for the treatment of bone diseases such as osteoporosis.

Van Wyk-Grumbach syndrome and oligosyndactyly in a 6-year-old girl: a case report

Background

Van Wyk-Grumbach syndrome refers to the development of isosexual precocious pseudopuberty and multicystic enlarged ovaries in the presence of hypothyroidism and delayed bone age. It is a rare presentation of untreated hypothyroidism. The prepubertal response in Van Wyk-Grumbach syndrome is always isosexual and mediated by very high thyroid-stimulating hormone levels acting through the follicle-stimulating hormone receptors inducing a follicle-stimulating hormonal effect. Early recognition and thyroid hormone replacement can completely regress precocious puberty and ovarian enlargement, while improving the final height achievement.

Oligosyndactly is a congenital bony abnormality and can manifest either as an isolated malformation or as a component of a syndromic diagnosis. However, development of hypothyroidism in children with this peculiar bony deformity has rarely been described in the medical literature, with the exception of Cenani-Lenz Syndactyly syndrome.

Case presentation

We report the case of a 6-year-old Sri Lankan girl who presented with a 2-day history of vaginal bleeding and exertional dyspnea. She had marked short stature (well below −3 standard deviations) with an upper segment to lower segment ratio of 1.47. This girl had isolated breast development of Tanner stage 2. She was diagnosed to have acquired hypothyroidism secondary to autoimmune thyroiditis and also had macrocytic anemia, pericardial effusion, gonadotropin-releasing hormone-independent precocious puberty with radiological evidence of pubertal changes in the uterus, and multicystic ovaries. Interestingly, she also had post-axial oligosyndactyly in both feet and right-sided clubfoot. The diagnosis of Van Wyk-Grumbach syndrome was made based on the clinical and laboratory features. Her symptoms were successfully managed with L-thyroxine therapy.

Conclusions

Acquired hypothyroidism is a relatively common endocrine disorder among children and early recognition is important to prevent serious complications like Van Wyk-Grumbach syndrome. Sexual precocity with delayed bone age and stunting should direct our minds toward this unique diagnosis. It is always necessary to identify the other associated anomalies in addition to the primary diagnosis since these features may direct to a syndromic diagnosis.

A novel biallelic splice-site variant in the LRP4 gene causes sclerosteosis 2

The LRP4 gene encodes the highly conserved low-density lipoprotein receptor-related protein 4 (LRP4), which acts as a co-receptor for sclerostin. Sclerostin and LRP4 negatively regulate WNT/β-catenin signaling pathway and lack of their inhibitory activity leads to constant osteoblastic differentiation. Consequently, increased bone formation occurs, which in the case of LRP4 mutations results in sclerosteosis type 2 (SOST2). Alterations within the LRP4 may also cause Cenani-Lenz syndactyly syndrome (CLSS), congenital myasthenia or isolated syndactyly. Here, we have reported a patient, in whom we found a novel homozygous splice-site variant c.1048+6T>C in LRP4 using whole exome sequencing. The patient was initially misdiagnosed with isolated CLSS-like or Malik-Percin-like syndactyly. However, we have finally refined the diagnosis after comprehensive radiological examination and molecularly confirmed SOST2. Additionally, we have pointed here to the splicing variants as important causative alterations that may be overlooked in the molecular analysis due to the lack of advanced, reliable algorithms, built-into the standard diagnostic pipelines. Using advanced in silico prediction tools of splice-site alterations, including Alamut Visual software, we have demonstrated that the c.1048+6T>C LRP4 variant affects the native donor site and impairs an SC35 enhancer activity. Based on our experience, we recommend comprehensive radiological imaging, including X-ray of the skull in each case of isolated syndactyly resulting from pathogenic variants of LRP4. We suggest that all previously reported patients carrying biallelic LRP4 mutations, who were diagnosed with isolated syndactyly, could actually present with SOST2 that had been unrecognized due to the incomplete clinical and radiological assessment.

Cenani-Lenz syndactyly in siblings with a novel homozygous LRP4 mutation and recurrent hypoglycaemia

Cenani-Lenz syndactyly (CLS) is a rare autosomal recessive syndrome characterized by disorganized oligosyndactyly of upper and lower limbs as well as radioulnar synostosis. Structural renal abnormalities are also common. We report two affected brothers, born to orthodox Jewish parents, in whom we found a novel homozygous missense variant c.4910G>A; p.(Cys1637Tyr) in LRP4 situated in an EGF-like domain between the fourth beta-propeller and transmembrane domains. Both brothers have had recurrent ketotic hypoglycaemia which has not been associated previously. We present 3D computed tomographic imaging illustrating the limb abnormalities in detail.