Skeletal phenotype in patients with Shwachman-Diamond syndrome and mutations in SBDS

Growth Charts for Shwachman-Diamond Syndrome at Ages 0 to 18 Years

Shwachman-Diamond syndrome (SDS) is one of the most common inherited bone marrow failure syndromes. SDS is characterized by hypocellular bone marrow, with a severe impairment of the myeloid lineage, resulting in neutropenia, thrombocytopenia, and, more rarely, anemia. Almost 15% of patients with SDS develop myelodysplastic syndrome or acute myeloid leukemia as early as childhood or young adulthood. Exocrine pancreatic insufficiency is another common feature of SDS. Almost all patients with SDS show failure to thrive, which is associated with skeletal abnormalities due to defective ossification. Considering these observations, it remains unfeasible to use the common growth charts already available for the general population. To address this issue, we report how we drew up growth charts of patients with SDS aged 0 to 18 years. We analyzed height, weight, and body max index (BMI) in 121 Italian patients with SDS. Results indicated that the 50th and 3rd percentiles of weight and height of the pediatric general population correspond to the 97th and 50th percentiles of patients with SDS aged 0-18 years, respectively. In addition, the percentage increment in weight of subjects aged 14-18 years was higher in patients with SDS than in the general population. SDS-specific growth charts, such as those described here, afford a new tool, which is potentially useful for both clinical and research purposes in SDS.

Knockdown of the Shwachman-Diamond syndrome gene, SBDS, induces galectin-1 expression and impairs cell growth

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by exocrine pancreatic insufficiency and bone marrow failure. The depletion of SBDS protein by RNA interference has been shown to cause inhibition of cell proliferation in several cell lines. However, the precise mechanism by which the loss of SBDS leads to inhibition of cell growth remains unknown. To evaluate the impaired growth of SBDS-knockdown cells, we analyzed Epstein-Barr virus-transformed lymphoblast cells (LCLs) derived from two patients with SDS (c. 183_184TA > CT and c. 258 + 2 T > C). After 3 days of culture, the growth of LCL-SDS cell lines was considerably less than that of control donor cells. By annealing control primer-based GeneFishing PCR screening, we found that galectin-1 (Gal-1) mRNA expression was elevated in LCL-SDS cells. Western blot analysis showed that the level of Gal-1 protein expression was also increased in LCL-SDS cells as well as in SBDS-knockdown 32Dcl3 murine myeloid cells. We confirmed that recombinant Gal-1 inhibited the proliferation of both LCL-control and LCL-SDS cells and induced apoptosis (as determined by annexin V-positive staining). These results suggest that the overexpression of Gal-1 contributes to abnormal cell growth in SBDS-deficient cells.

Characteristics of Craniofacial Morphology and Occlusion in Shwachman-Diamond Syndrome: A Case Report of a Japanese Sibling Pair

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder mainly caused by mutations in the Shwachman-Bodian-Diamond syndrome gene on chromosome 7q11. Although skeletal abnormalities are a feature of SDS, no reports have focused on the craniofacial morphology of patients with SDS. Moreover, the detailed dental characteristics of SDS remain unknown. In the present case report, we evaluated the craniofacial morphology and dental findings of two patients with SDS. A Japanese adolescent sibling pair with SDS had the chief complaint of excessive overjet. Cephalometric analysis revealed similar craniofacial morphology in both patients: skeletal class I malocclusion with a hypodivergent pattern and labial inclination of the maxillary and mandibular incisors. A panoramic photograph showed the tendency of delayed permanent tooth eruption and replacement in both patients. These cases suggest that malocclusion requiring orthodontic treatment might be a feature of patients with SDS.

M phase-specific interaction between SBDS and RNF2 at the mitotic spindles regulates mitotic progression

Shwachman-Diamond syndrome (SDS) is an autosomal recessive inherited disorder caused by biallelic mutations in the Shwachman-Bodian-Diamond syndrome (SBDS) gene. SBDS protein is involved in ribosome biogenesis; therefore SDS is classified as a ribosomopathy. SBDS is localized at mitotic spindles and stabilizes microtubules. Previously, we showed that SBDS interacts with ring finger protein 2 (RNF2) and is degraded through RNF2-dependent ubiquitination. In this study, we investigated when and where SBDS interacts with RNF2 and the effects of the interaction on cells. We found that SBDS co-localized with RNF2 on centrosomal microtubules in the mitotic phase (M phase), whereas SBDS and RNF2 localized to the nucleolus and nucleoplasm in the interphase, respectively. The microtubule-binding assay revealed that SBDS interacted directly with microtubules and RNF2 interacted with SBDS bound to microtubules. In addition, SBDS was ubiquitinated and degraded by RNF2 during the M phase. Moreover, RNF2 overexpression accelerated mitotic progression. These findings suggest that SBDS delays mitotic progression, and RNF2 releases cells from suppression through the ubiquitination and subsequent degradation of SBDS. The interaction between SBDS and RNF2 at mitotic spindles might be involved in mitotic progression as a novel regulatory cascade.

An Unusual Presentation of Extremely Early Neonatal Cirrhosis in Shwachman-Diamond Syndrome: A Case Report

Exocrine pancreatic insufficiency, haematological dysfunction, and skeletal abnormalities are the three clinical characteristics of the rare inherited bone marrow failure syndrome (IBMFS), known as Shwachman-Diamond syndrome (SDS). Cirrhosis at a neonatal age is uncommon and is typically not documented, as in neonatal presentation. Here, we present a case of SDS in which bi-cytopenia with macro-nodular cirrhosis emerged before the age of one month. Utilising genetic testing on the infant and both parents, we were able to confirm the diagnosis. We were expecting a higher-level liver transplant set-up, but the infant passed away in the interim. Genetic studies play a significant part in the diagnosis of difficult cases.

Predisposition to myeloid malignancies in Shwachman-Diamond syndrome: biological insights and clinical advances

Shwachman-Diamond syndrome (SDS) is an inherited multisystem ribosomopathy characterized by exocrine pancreatic deficiency, bone marrow failure, and predisposition to myeloid malignancies. The pathobiology of SDS results from impaired ribosomal maturation due to the deficiency of SBDS and the inability to evict the antiassociation factor eIF6 from the 60S ribosomal subunit. Clinical outcomes for patients with SDS who develop myeloid malignancies are extremely poor because of high treatment-related toxicities and a high rate of refractory disease/relapse even after allogeneic hematopoietic stem cell transplant (HSCT). Registry data indicate that outcomes are improved for patients with SDS who undergo routine bone marrow surveillance and receive an HSCT before developing an overt malignancy. However, the optimal approach to hematologic surveillance and the timing of HSCT for patients with SDS is not clearly established. Recent studies have elucidated distinct patterns of somatic blood mutations in patients with SDS that either alleviate the ribosome defect via somatic rescue (heterozygous EIF6 inactivation) or disrupt cellular checkpoints, resulting in increased leukemogenic potential (heterozygous TP53 inactivation). Genomic analysis revealed that most myeloid malignancies in patients with SDS have biallelic loss-of-function TP53 mutations. Single-cell DNA sequencing of SDS bone marrow samples can detect premalignant biallelic TP53-mutated clones before clinical diagnosis, suggesting that molecular surveillance may enhance the detection of incipient myeloid malignancies when HSCT may be most effective. Here, we review the clinical, genetic, and biologic features of SDS. In addition, we present evidence supporting the hematologic surveillance for patients with SDS that incorporates clinical, pathologic, and molecular data to risk stratify patients and prioritize transplant evaluation for patients with SDS with high-risk features.

Improved detection of SBDS gene mutation by a new method of next-generation sequencing analysis based on the Chinese mutation spectrum

Next-generation sequencing (NGS) is a useful molecular diagnostic tool for genetic diseases. However, due to the presence of highly homologous pseudogenes, it is challenging to use short-read NGS for analyzing mutations of the Shwachman-Bodian-Diamond syndrome (SBDS) gene. The SBDS mutation spectrum was analyzed in the Chinese population, which revealed that SBDS variants were primarily from sequence exchange between SBDS and its pseudogene at the base-pair level, predominantly in the coding region and splice junction of exon two. The c.258+2T>C and c.185_184TA>GT variants were the two most common pathogenic SBDS variants in the Chinese population, resulting in a total carrier frequency of 1.19%. When analyzing pathogenic variants in the SBDS gene from the NGS data, the misalignment was identified as a common issue, and there were different probabilities of misalignment for different pathogenic variants. Here, we present a novel mathematical method for identifying pathogenic variants in the SBDS gene from the NGS data, which utilizes read-depth of the paralogous sequence variant (PSV) loci of SBDS and its pseudogene. Combined with PCR and STR orthogonal experiments, SBDS gene mutation analysis results were improved in 40% of clinical samples, and various types of mutations such as homozygous, compound heterozygous, and uniparental diploid were explored. The findings effectively reduce the impact of misalignment in NGS-based SBDS mutation analysis and are helpful for the clinical diagnosis of SBDS-related diseases, the research into population variation, and the carrier screening.

Shwachman Diamond Syndrome with Arrhythmia as the First Manifestation a Case Report and Literature Review

Objective

Analyze the different clinical manifestations and genetic characteristics of Shwachman diamond syndrome (SDS).

Methods

The clinical data of a case of neonatal onset Shwachman diamond syndrome with arrhythmia as the first manifestation were retrospectively analyzed, and the relevant literature was reviewed to summarize the clinical manifestations, genetic characteristics and treatment of Shwachman diamond syndrome.

Results

The patient, female, age 1 month 24 days, with ventricular arrhythmia as the first manifestation, accompanied by growth retardation, liver damage, and persistent decrease in peripheral blood neutrophil count (< 1.5 × 10⁹/l), no pancreatic exocrine gland dysfunction at the initial stage of the disease. Gene detection showed that the SBDS gene chr7:66,459,197, c.258+2T > C homozygous variation.

Conclusion

Although the classic manifestations of Shwachman diamond syndrome are pancreatic exocrine insufficiency, pancreatic adiposis and unexplained neutropenia, its clinical manifestations are complex and diverse, involving multiple systems. For suspected children, early genetic examination is helpful for subsequent diagnosis and treatment.

Exploring and expanding the phenotype and genotype diversity in seven Chinese families with spondylo-epi-metaphyseal dysplasia

Spondylo-epi-metaphyseal dysplasia (SEMD) is a heterogeneous group of disorders with different modes of inheritance and is characterized by disproportionate or proportionate short stature. To date, more than 30 disease-causing genes have been identified, and different types of SEMD exhibit greatly overlapping clinical features, which usually complicate the diagnosis. This study was performed to expand the clinical and molecular spectrum of SEMD among Chinese subjects and to explore their potential phenotype–genotype relations. We enrolled seven families including 11 affected patients with SEMD, and their clinical, radiographic, and genetic data were carefully analyzed. All the seven probands showed different degrees of short stature, and each of them exhibited additional specific skeletal manifestations; four probands had extraosseous manifestations. X-rays of the seven probands showed common features of SEMD, including vertebral deformities, irregular shape of the epiphysis, and disorganization of the metaphysis. Seven variants were identified in TRPV4 (c.694C&gt; T, p.Arg232Cys), COL2A1 (c.654 + 1G &gt; C; c.3266_3268del, p.Gly1089del), CCN6 (c.396 T&gt; G, p.Cys132Trp; c.721 T&gt;C, p.Cys241Arg), SBDS (c.258 + 2T&gt; C), and ACAN (c.1508C&gt; A, p.Thr503Lys) genes, and two of them were novel. Two families with TRPV4 variants showed considerable intrafamily and interfamily heterogeneities. In addition, we reported one case of SEMD with a severe phenotype caused by ACAN gene mutation. Our study expands the phenotype and genetic spectrum of SEMD and provides evidence for the phenotype–genotype relations, aiding future molecular and clinical diagnosis as well as procreative management of SEMD.

Enhanced p53 Levels Are Involved in the Reduced Mineralization Capacity of Osteoblasts Derived from Shwachman-Diamond Syndrome Subjects

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, caused by loss-of-function mutations in the SBDS gene, a factor involved in ribosome biogenesis. By analyzing osteoblasts from SDS patients (SDS-OBs), we show that SDS-OBs displayed reduced SBDS gene expression and reduced/undetectable SBDS protein compared to osteoblasts from healthy subjects (H-OBs). SDS-OBs cultured in an osteogenic medium displayed a lower mineralization capacity compared to H-OBs. Whole transcriptome analysis showed significant differences in the gene expression of SDS-OBs vs. H-OBs, particularly in the ossification pathway. SDS-OBs expressed lower levels of the main genes responsible for osteoblastogenesis. Of all downregulated genes, Western blot analyses confirmed lower levels of alkaline phosphatase and collagen type I in SDS-OBs than in H-OBs. Interestingly, SDS-OBs showed higher protein levels of p53, an inhibitor of osteogenesis, compared to H-OBs. Silencing of Tp53 was associated with higher collagen type I and alkaline phosphatase protein levels and an increase in SDS-OB mineralization capacity. In conclusion, our results show that the reduced capacity of SDS-OBs to mineralize is mediated, at least in part, by the high levels of p53 and highlight an important role of SBDS in osteoblast functions.

Diagnostic work-up for severe aplastic anemia in children: Consensus of the North American Pediatric Aplastic Anemia Consortium

The North American Pediatric Aplastic Anemia Consortium (NAPAAC) is a group of pediatric hematologist-oncologists, hematopathologists, and bone marrow transplant physicians from 46 institutions in North America with interest and expertise in aplastic anemia, inherited bone marrow failure syndromes, and myelodysplastic syndromes. The NAPAAC Bone Marrow Failure Diagnosis and Care Guidelines Working Group was established with the charge of harmonizing the approach to the diagnostic workup of aplastic anemia in an effort to standardize best practices in the field. This document outlines the rationale for initial evaluations in pediatric patients presenting with signs and symptoms concerning for severe aplastic anemia.

Distinguishing constitutional from acquired bone marrow failure in the hematology clinic

Distinguishing constitutional from immune bone marrow failure (BMF) has important clinical implications. However, the diagnosis is not always straightforward, and immune aplastic anemia, the commonest BMF, is a diagnosis of exclusion. In this review, we discuss a general approach to the evaluation of BMF, focusing on clinical presentations particular to immune and various constitutional disorders as well as the interpretation of bone marrow histology, flow cytometry, and karyotyping. Additionally, we examine the role of specialized testing in both immune and inherited BMF, and discuss genetic testing, both its role in patient evaluation and interpretation of results.

Shwachman-diamond syndrome: A case report

RATIONALE

The aim of this study was to analyze the genetic abnormalities and clinical manifestations of Shwachman-Diamond syndrome (SDS).

PATIENT CONCERNS

A Chinese infant with elevated transaminase and a novel mutation at of sbdsc.258 +2T>C and c.184a>Tc.292G>A.

DIAGNOSES

The female patient was 5 months' old at onset, with elevated transaminase as the first manifestation accompanied by restricted growth and development and oily stool. After sequencing the blood samples from patients and their parents, the heterozygous mutations of sbdsc.258 +2T>C and c.184a>T were detected.

INTERVENTIONS

After admission, the patient was provided compound glycyrrhizin, Newtide formula milk supplemented with probiotics, fat-soluble vitamins, oral medication to adjust the spleen and stomach, and other symptomatic treatments.

OUTCOMES

The stool traits improved, and the levels of liver function transaminases decreased compared with before.

LESSONS

SDS is a rare disease with a variety of clinical manifestations. Pancreatic exocrine dysfunction, blood system manifestations, and bone abnormalities are common clinical manifestations, and genetic testing is helpful for diagnosis.

Somatic development in children with Shwachman-Diamond syndrome

BACKGROUND

Shwachman-Diamond syndrome (SDS) is a rare genetic, multi-systemic disease characterized by exocrine pancreatic insufficiency, immune deficiency, bone marrow failure and skeletal abnormalities. Most patients present with failure in somatic development and short stature, but systematic data concerning those features are limited. The aim of the study was to assess the prevalence of failure in somatic development in the children with SDS.

METHODS

An analysis of anthropometric measurements of 21 patients (14 girls and 7 boys),aged 2 to 17 years (mean age 6.3 years) with SDS diagnosed in The Children's Memorial Health Institute in Warsaw, Poland was performed. The patients were measured using a Holtain Limited stadiometer, an electronic scale, a Harpenden anthropometer, a metric tape and a spreading caliper. The assessed anthropometric parameters were expressed as standard deviation scores in relation to the reference values in Poland, suitable for sex as well as calendar and growth age.

RESULTS

A total of 66 measurements was collected and analyzed with a median number of 3 observations per patient. The group of boys presented with a significantly lower height (- 3.0 SD, p < 0.0001) and BMI (- 1.4 SD, p < 0.00001), and in the relation to the growth age a lower weight (- 1.0 SD, p < 0.001) as well as a smaller chest width (- 0.9 SD, p < 0.05), hip width (- 0,5 SD, p < 0,05) and lower limb length (- 0,5 SD, p < 0,05). The group of girls also showed significantly lower height (- 2.6 SD, p < 0.00001) and BMI (- 0.8 SD, p < 0.00001), and in relation to the growth age, lower weight (- 0.5 SD, p < 0.001) as well as decreased width of the chest (- 1.7 SD, p < 0.0001) and shoulder (- 1.0 SD, p < 0.001) were observed. Boys and girls were also characterized by significantly decreased circumference and width of head, additionally, girls had also smaller head length.

CONCLUSIONS

Patients with SDS have abnormal somatic development. Both boys and girls are characterized by short stature, decreased weight, BMI, leg length, chest width as well as circumference and width of head. Anthropometric measurements provide important data on the process of growth and body proportions in children with SDS.

Disruption in iron homeostasis and impaired activity of iron-sulfur cluster containing proteins in the yeast model of Shwachman-Diamond syndrome

BACKGROUND

Shwachman-Diamond syndrome (SDS) is a congenital disease that affects the bone marrow, skeletal system, and pancreas. The majority of patients with SDS have mutations in the SBDS gene, involved in ribosome biogenesis as well as other processes. A Saccharomyces cerevisiae model of SDS, lacking Sdo1p the yeast orthologue of SBDS, was utilized to better understand the molecular pathogenesis in the development of this disease.

RESULTS

Deletion of SDO1 resulted in a three-fold over-accumulation of intracellular iron. Phenotypes associated with impaired iron-sulfur (ISC) assembly, up-regulation of the high affinity iron uptake pathway, and reduced activities of ISC containing enzymes aconitase and succinate dehydrogenase, were observed in sdo1∆ yeast. In cells lacking Sdo1p, elevated levels of reactive oxygen species (ROS) and protein oxidation were reduced with iron chelation, using a cell impermeable iron chelator. In addition, the low activity of manganese superoxide dismutase (Sod2p) seen in sdo1∆ cells was improved with iron chelation, consistent with the presence of reactive iron from the ISC assembly pathway. In yeast lacking Sdo1p, the mitochondrial voltage-dependent anion channel (VDAC) Por1p is over-expressed and its deletion limits iron accumulation and increases activity of aconitase and succinate dehydrogenase.

CONCLUSIONS

We propose that oxidative stress from POR1 over-expression, resulting in impaired activity of ISC containing proteins and disruptions in iron homeostasis, may play a role in disease pathogenesis in SDS patients.

Shwachman-Diamond Syndrome: Molecular Mechanisms and Current Perspectives

Shwachman-Diamond syndrome (SDS) is a rare inherited disease mainly caused by mutations in the Shwachman-Bodian-Diamond Syndrome (SBDS) gene. However, it has recently been reported that other genes, including DnaJ heat shock protein family (Hsp40) member C21 (DNAJC21), elongation factor-like 1 (EFL1) and signal recognition particle 54 (SRP54) are also associated with an SDS-like phenotype. Interestingly, SBDS, DNAJC21, EFL1 and SRP54 are involved in ribosome biogenesis: SBDS, through direct interaction with EFL1, promotes the release of the eukaryotic initiation factor 6 (eIF6) during ribosome maturation, DNAJC21 stabilizes the 80S ribosome, and SRP54 facilitates protein trafficking. These findings strengthen the postulate that SDS is a ribosomopathy. SDS is a multiple-organ disease mainly characterized by bone marrow failure, bone malformations, pancreatic insufficiency and cognitive disorders. Almost 15-20% of patients with SDS present myelodysplastic syndrome with a high risk of acute myeloid leukemia (AML) transformation. Unfortunately, besides bone marrow transplantation, no gene-based therapy for SDS has yet been developed. This review aims to recapitulate the recent findings on the molecular mechanisms of SDS underlying bone marrow failure, hematopoiesis and AML development and to draw a realistic picture of current perspectives.

Decreased accumulation of superoxide dismutase 2 within mitochondria in the yeast model of Shwachman-Diamond syndrome

Mutations in the human SBDS gene is the most common cause of Shwachman-Diamond syndrome (SDS). The SBDS protein participates in ribosome biogenesis; however, effects beyond reduced translation efficiency are thought to be involved in SDS progression. Impaired mitochondrial function has been reported for cells lacking either SBDS or Sdo1p, the Saccharomyces cerevisiae SBDS ortholog. To better understand how the loss of SBDS/Sdo1p leads to mitochondria damage, we utilized the S. cerevisiae model of SDS. Yeast deleted for SDO1 show increased oxidative damage to mitochondrial proteins and a marked decrease in protein levels and activity of mitochondrial superoxide dismutase 2 (Sod2p), a key enzyme involved in defense against oxidants. Immature forms of Sod2p are observed in sdo1∆ cells suggesting a defect in proteolysis of the presequence. Yeast deleted for CYM1, encoding a presequence protease, display a similar reduction in Sod2p activity as sdo1∆ cells, as well as elevated oxidative damage, to mitochondrial proteins. Sod2p protein levels and activity are largely restored in a por1∆ sdo1∆ strain, lacking the major mitochondrial voltage-dependent anion channel. Together these results indicate that mitochondrial insufficiency in sdo1∆ cells may be linked to the accumulation of immature presequence containing proteins and this effect is a consequence, at least in part, from loss of counter-regulation of Por1p by Sdo1p.

Normative growth charts for Shwachman-Diamond syndrome from Italian cohort of 0-8 years old

OBJECTIVES

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder. Its predominant manifestations include exocrine pancreatic insufficiency, bone marrow failure and skeletal abnormalities. Patients frequently present failure to thrive and susceptibility to short stature. Average birth weight is at the 25th percentile; by the first birthday, >50% of patients drop below the third percentile for height and weight.The study aims at estimating the growth charts for patients affected by SDS in order to give a reference tool helpful for medical care and growth surveillance through the first 8 years of patient's life.

SETTING AND PARTICIPANTS

This retrospective observational study includes 106 patients (64 M) with available information from birth to 8 years, selected among the 122 patients included in the Italian National Registry of SDS and born between 1975 and 2016. Gender, birth date and auxological parameters at repeated assessment times were collected. The General Additive Model for Location Scale and Shape method was applied to build the growth charts. A set of different distributions was used, and the more appropriate were selected in accordance with the smallest Akaike information criterion.

RESULTS

A total of 408 measurements was collected and analysed. The median number of observations per patient amounted to 3, range 1-11. In accordance with the methods described, specific SDS growth charts were built for weight, height and body mass index (BMI), separately for boys and girls.The 50th and 3rd percentiles of weight and height of the healthy population (WHO standard references) respectively correspond to the 97th and 50th percentiles of the SDS population (SDS specific growth charts), while the difference is less evident for the BMI.

CONCLUSIONS

Specific SDS growth charts obtained through our analysis enable a more appropriate classification of patients based on auxological parameters, representing a useful reference tool for evaluating their growth during childhood.

Peering through zebrafish to understand inherited bone marrow failure syndromes

Inherited bone marrow failure syndromes are experiments of nature characterized by impaired hematopoiesis with cancer and leukemia predisposition. The mutations associated with inherited bone marrow failure syndromes affect fundamental cellular pathways, such as DNA repair, telomere maintenance, or proteostasis. How these disturbed pathways fail to produce sufficient blood cells and lead to leukemogenesis are not understood. The rarity of inherited cytopenias, the paucity of affected primary human hematopoietic cells, and the sometime inadequacy of murine or induced pluripotential stem cell models mean it is difficult to acquire a greater understanding of them. Zebrafish offer a model organism to study gene functions. As vertebrates, zebrafish share with humans many orthologous genes involved in blood disorders. As a model organism, zebrafish provide advantages that include rapid development of transparent embryos, high fecundity (providing large numbers of mutant and normal siblings), and a large collection of mutant and transgenic lines useful for investigating the blood system and other tissues during development. Importantly, recent advances in genomic editing in zebrafish can speedily validate the new genes or novel variants discovered in clinical investigation as causes for marrow failure. Here we review zebrafish as a model organism that phenocopies Fanconi anemia, Diamond-Blackfan anemia, dyskeratosis congenita, Shwachman-Diamond syndrome, congenital amegakaryocytic thrombocytopenia, and severe congenital neutropenia. Two important insights, provided by modeling inherited cytopenias in zebrafish, widen understanding of ribosome biogenesis and TP53 in mediating marrow failure and non-hematologic defects. They suggest that TP53-independent pathways contribute to marrow failure. In addition, zebrafish provide an attractive model organism for drug development.

A Case of Shwachman-Diamond Syndrome who Presented with Hypotonia

We present a patient with failure to thrive and severe hypotonia, who was initially suspected of having a neurometabolic disease but later diagnosed as Shwachman-Diamond syndrome (SDS), which was genetically confirmed. SDS is a multisystemic disease, which is characterized by exocrine pancreatic deficiency, bone marrow dysfunction with increased risk for malignant transformation, and skeletal abnormalities. It should be included in differential diagnosis of patients with failure to thrive and unexplained neurodevelopmental delay with neutropenia.

Short stature: an ordinary sign for an unordinary diagnosis

Background

Case presentation

Conclusions

Molecular basis of the human ribosomopathy Shwachman-Diamond syndrome

Mutations that target the ubiquitous process of ribosome assembly paradoxically cause diverse tissue-specific disorders (ribosomopathies) that are often associated with an increased risk of cancer. Ribosomes are the essential macromolecular machines that read the genetic code in all cells in all kingdoms of life. Following pre-assembly in the nucleus, precursors of the large 60S and small 40S ribosomal subunits are exported to the cytoplasm where the final steps in maturation are completed. Here, I review the recent insights into the conserved mechanisms of ribosome assembly that have come from functional characterisation of the genes mutated in human ribosomopathies. In particular, recent advances in cryo-electron microscopy, coupled with genetic, biochemical and prior structural data, have revealed that the SBDS protein that is deficient in the inherited leukaemia predisposition disorder Shwachman-Diamond syndrome couples the final step in cytoplasmic 60S ribosomal subunit maturation to a quality control assessment of the structural and functional integrity of the nascent particle. Thus, study of this fascinating disorder is providing remarkable insights into how the large ribosomal subunit is functionally activated in the cytoplasm to enter the actively translating pool of ribosomes.

Biallelic mutations in DNAJC21 cause Shwachman-Diamond syndrome

There is an Inside Blood Commentary on this article in this issue.

Neonatal manifestations of inherited bone marrow failure syndromes

The inherited bone marrow failure syndromes (IBMFS) are a rare yet clinically important cause of neonatal hematological and non-hematological manifestations. Many of these syndromes, such as Fanconi anemia, dyskeratosis congenita and Diamond-Blackfan anemia, confer risks of multiple medical complications later in life, including an increased risk of cancer. Some IBMFS may present with cytopenias in the neonatal period whereas others may present only with congenital physical abnormalities and progress to pancytopenia later in life. A thorough family history and detailed physical examination are integral to the work-up of any neonate in whom there is a high index of suspicion for an IBMFS. Correct detection and diagnosis of these disorders is important for appropriate long-term medical surveillance and counseling not only for the patient but also for appropriate genetic counselling of their families regarding recurrence risks in future children and generations.

Cartilage–hair hypoplasia: a spectrum of clinical and radiological findings

Introduction: Cartilage–hair hypoplasia (CHH) is a rare skeletal dysplasia that presents with various degrees of immunodeficiency, short stature, and a susceptibility to malignancies. Individuals with CHH can present with severe combined immunodeficiency or combined immunodeficiency and are at risk for severe and unusual infections irrespective of their laboratory findings. In addition, individuals with CHH can present with variable skeletal abnormalities, mainly involving the metaphysis of long bones. CHH is a rare disease and familiarity with the variable features is crucial for diagnosis.

Methods: We report the clinical, radiological, and genetic findings for 5 patients with proven diagnoses of CHH.

Results: In this study we describe a cohort of patients with CHH and present their clinical findings and progressions. In addition, we present the radiological images and the immunological investigations that were done in these patients. Although all the patients in our cohort had poor cellular immunity, they had a variable clinical course. Three out of 5 patients received a bone marrow transplant (BMT) and 2 out of 5 died at an early age (1 after BMT). Those who had poor humoral function had a worse prognosis compared with those with good humoral function. The skeletal findings were characteristic for CHH.

Conclusion: CHH is a disease with a variable presentation. Clinicians should be aware of the characteristic skeletal and immunological findings to identify the disease as early as possible.

Statement of novelty: We present novel clinical and radiological findings in patients with variable RMRP gene mutations.

Radiosensitivity in lymphoblastoid cell lines derived from Shwachman-Diamond syndrome patients

Shwachman-Diamond syndrome is an autosomal-recessive disorder characterised by bone marrow failure and a cumulative risk of progression to acute myeloid leukaemia. The Shwachman-Bodian-Diamond syndrome (SBDS) gene, the only gene known to be causative of the pathology, is involved in ribosomal biogenesis, stress responses and DNA repair, and the lack of SBDS sensitises cells to many stressors and leads to mitotic spindle destabilisation. The effect of ionising radiation on SBDS-deficient cells was investigated using immortalised lymphocytes from SDS patients in comparison with positive and negative controls in order to test whether, in response to ionising radiation exposure, any impairment in the DNA repair machinery could be observed. After irradiating cells with different doses of X-rays or gamma-rays, DNA repair kinetics and the residual damages using the alkaline COMET assay and the γ-H2AX assay were assessed, respectively. In this work, preliminary data about the comparison between ionising radiation effects in different patients-derived cells and healthy control cells are presented.

Shwachman-Bodian-Diamond syndrome: metaphyseal chondrodysplasia in children with pancreatic insufficiency and neutropenia

Shwachman-Bodian-Diamond syndrome (OMIM 260400) was identified in 1964 by pediatricians Harry Shwachman, a leader in cystic fibrosis, and Louis K. Diamond, a hematologist, along with pediatrician and morbid anatomist Martin Bodian. Initially the syndrome's clinical presentation included exocrine pancreatic insufficiency (lipomatous replacement of the pancreas) and neutropenia. In 1967 skeletal changes of metaphyseal chondrodysplasia were also described, completing the triad of findings; these abnormalities are present in all affected children and should be viewed as an integral feature of the syndrome, also called Shwachman-Diamond syndrome.

In Vivo Senescence in the Sbds-Deficient Murine Pancreas: Cell-Type Specific Consequences of Translation Insufficiency

Genetic models of ribosome dysfunction show selective organ failure, highlighting a gap in our understanding of cell-type specific responses to translation insufficiency. Translation defects underlie a growing list of inherited and acquired cancer-predisposition syndromes referred to as ribosomopathies. We sought to identify molecular mechanisms underlying organ failure in a recessive ribosomopathy, with particular emphasis on the pancreas, an organ with a high and reiterative requirement for protein synthesis. Biallelic loss of function mutations in SBDS are associated with the ribosomopathy Shwachman-Diamond syndrome, which is typified by pancreatic dysfunction, bone marrow failure, skeletal abnormalities and neurological phenotypes. Targeted disruption of Sbds in the murine pancreas resulted in p53 stabilization early in the postnatal period, specifically in acinar cells. Decreased Myc expression was observed and atrophy of the adult SDS pancreas could be explained by the senescence of acinar cells, characterized by induction of Tgfβ, p15^Ink4b and components of the senescence-associated secretory program. This is the first report of senescence, a tumour suppression mechanism, in association with SDS or in response to a ribosomopathy. Genetic ablation of p53 largely resolved digestive enzyme synthesis and acinar compartment hypoplasia, but resulted in decreased cell size, a hallmark of decreased translation capacity. Moreover, p53 ablation resulted in expression of acinar dedifferentiation markers and extensive apoptosis. Our findings indicate a protective role for p53 and senescence in response to Sbds ablation in the pancreas. In contrast to the pancreas, the Tgfβ molecular signature was not detected in fetal bone marrow, liver or brain of mouse models with constitutive Sbds ablation. Nevertheless, as observed with the adult pancreas phenotype, disease phenotypes of embryonic tissues, including marked neuronal cell death due to apoptosis, were determined to be p53-dependent. Our findings therefore point to cell/tissue-specific responses to p53-activation that include distinction between apoptosis and senescence pathways, in the context of translation disruption.

Growth of all living things relies on protein synthesis. Failure of components of the complex protein synthesis machinery underlies a growing list of inherited and acquired multi—organ syndromes referred to as ribosomopathies. While ribosomes, the critical working components of the protein synthesis machinery, are required in all cell types to translate the genetic code, only certain organs manifest clinical symptoms in ribosomopathies, indicating specific cell-type features of protein synthesis control. Further, many of these diseases result in cancer despite an inherent deficit in growth. Here we report a range of consequences of protein synthesis insufficiency with loss of a broadly expressed ribosome factor, leading to growth impairment and cell cycle arrest at different stages. Apparent induction of p53-dependent cell death and arrest pathways included apoptosis in the fetal brain and senescence in the mature exocrine pancreas. The senescence, considered a tumour suppression mechanism, was accompanied by the expression of biomarkers associated with early stages of malignant transformation. These findings inform how cancer may initiate when growth is compromised and provide new insights into cell-type specific consequences of protein synthesis insufficiency.

Joint eQTL assessment of whole blood and dura mater tissue from individuals with Chiari type I malformation

BACKGROUND

Expression quantitative trait loci (eQTL) play an important role in the regulation of gene expression. Gene expression levels and eQTLs are expected to vary from tissue to tissue, and therefore multi-tissue analyses are necessary to fully understand complex genetic conditions in humans. Dura mater tissue likely interacts with cranial bone growth and thus may play a role in the etiology of Chiari Type I Malformation (CMI) and related conditions, but it is often inaccessible and its gene expression has not been well studied. A genetic basis to CMI has been established; however, the specific genetic risk factors are not well characterized.

RESULTS

We present an assessment of eQTLs for whole blood and dura mater tissue from individuals with CMI. A joint-tissue analysis identified 239 eQTLs in either dura or blood, with 79% of these eQTLs shared by both tissues. Several identified eQTLs were novel and these implicate genes involved in bone development (IPO8, XYLT1, and PRKAR1A), and ribosomal pathways related to marrow and bone dysfunction, as potential candidates in the development of CMI.

CONCLUSIONS

Despite strong overall heterogeneity in expression levels between blood and dura, the majority of cis-eQTLs are shared by both tissues. The power to detect shared eQTLs was improved by using an integrative statistical approach. The identified tissue-specific and shared eQTLs provide new insight into the genetic basis for CMI and related conditions.

Inherited bone marrow failure syndromes in adolescents and young adults

The inherited bone marrow failure syndromes are a diverse group of genetic diseases associated with inadequate production of one or more blood cell lineages. Examples include Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan anemia, thrombocytopenia absent radii syndrome, severe congenital neutropenia, and Shwachman-Diamond syndrome. The management of these disorders was once the exclusive domain of pediatric subspecialists, but increasingly physicians who care for adults are being called upon to diagnose or treat these conditions. Through a series of patient vignettes, we highlight the clinical manifestations of inherited bone marrow failure syndromes in adolescents and young adults. The diagnostic and therapeutic challenges posed by these diseases are discussed.

The ever-expanding conundrum of primary osteoporosis: aetiopathogenesis, diagnosis, and treatment

In recent years, as knowledge regarding the etiopathogenetic mechanisms of bone involvement characterizing many diseases has increased and diagnostic techniques evaluating bone health have progressively improved, the problem of low bone mass/quality in children and adolescents has attracted more and more attention, and the body evidence that there are groups of children who may be at risk of osteoporosis has grown. This interest is linked to an increased understanding that a higher peak bone mass (PBM) may be one of the most important determinants affecting the age of onset of osteoporosis in adulthood. This review provides an updated picture of bone pathophysiology and characteristics in children and adolescents with paediatric osteoporosis, taking into account the major causes of primary osteoporosis (PO) and evaluating the major aspects of bone densitometry in these patients. Finally, some options for the treatment of PO will be briefly discussed.

Ribosome biogenesis in skeletal development and the pathogenesis of skeletal disorders

The skeleton affords a framework and structural support for vertebrates, while also facilitating movement, protecting vital organs, and providing a reservoir of minerals and cells for immune system and vascular homeostasis. The mechanical and biological functions of the skeleton are inextricably linked to the size and shape of individual bones, the diversity of which is dependent in part upon differential growth and proliferation. Perturbation of bone development, growth and proliferation, can result in congenital skeletal anomalies, which affect approximately 1 in 3000 live births [1]. Ribosome biogenesis is integral to all cell growth and proliferation through its roles in translating mRNAs and building proteins. Disruption of any steps in the process of ribosome biogenesis can lead to congenital disorders termed ribosomopathies. In this review, we discuss the role of ribosome biogenesis in skeletal development and in the pathogenesis of congenital skeletal anomalies. This article is part of a Special Issue entitled: Role of the Nucleolus in Human Disease.

Misdiagnosis as asphyxiating thoracic dystrophy and CMV-associated haemophagocytic lymphohistiocytosis in Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterised by skeletal dysplasia, exocrine pancreatic insufficiency and bone marrow failure. Various other conditions, such as hepatopathy and failure to thrive have been associated with SDS. A retrospective study was conducted to describe mutations, clinical features, and the immunological profile of 11 Belgian patients with genetically confirmed diagnosis of SDS. This study confirms the existing understanding of the classical features of SDS although the typical triad was present in only six out of nine fully studied patients. The following important observations are made in this cohort. Four out of eleven patients were misdiagnosed as having Asphyxiating Thoracic Dystrophy (Jeune syndrome) because of severe thoracic dystrophy. Another two patients presented with unexplained episodes of symptomatic hypoglycaemia. The immunological phenotype was heterogeneous although laboratory abnormalities were noticed in eight out of ten patients assessed. Three patients experienced a life threatening viral infection (respiratory syncytial virus, cytomegalovirus (CMV) and rotavirus). In one patient, CMV infection caused an episode of haemophagocytic lymphohistiocytosis. One patient has bronchiectasis at the age of 3 years due to recurrent respiratory tract infections. These findings strengthen the suspicion of an abnormal immune system in SDS. Liver anomalies, usually described as benign and transitory in SDS patients, were severe in two patients of the cohort. One patient developed hepatopulmonary syndrome. The findings in this national cohort of SDS patients could contribute to the prevention of misdiagnosis in the future and enable more rapid recognition of certain severe complications.

A clinical algorithm predicts hematological complications in Shwachman-Diamond syndrome?

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disease caused by mutations in the SBDS gene in approximately 90% of cases. SDS is characterized by exocrine pancreatic insufficiency and bone marrow failure, which predisposes to the development of myelodysplastic syndrome and/or acute myeloid leukemia. In a new report, the French national cohort studied 102 SDS patients with a median follow-up of 11.6 years, focusing on the natural history of severe cytopenias. The authors concluded that SDS patients with a young age (<3 months) at first symptomatic presentation or cytopenia at diagnosis were at a high risk of subsequent severe hematological complications (either malignant or nonmalignant). Their findings raise the possibility that a clinical algorithm may predict the subsequent development of hematological complications in SDS.

Clinical and molecular pathophysiology of Shwachman-Diamond syndrome: an update

Shwachman-Diamond syndrome (SDS) is an inherited neutropenia syndrome associated with a significant risk of aplastic anemia and malignant transformation. Multiple additional organ systems, including the pancreas, liver, and skeletal and central nervous systems, are affected. Mutations in the Shwachman-Bodian-Diamond syndrome (SBDS) gene are present in most patients. There is growing evidence that SBDS functions in ribosomal biogenesis and other cellular processes. This article summarizes the clinical phenotype of SDS, diagnostic and treatment approaches, and novel advances in our understanding of the molecular pathophysiology of this disease.

Subglottic stenosis in Shwachman-Diamond syndrome - is there a link?

Clinically relevant cartilaginous subglottic stenosis was found in 2 patients with Shwachman-Diamond syndrome (SDS) for which tracheotomy was required in one case. Considering the pathogenesis of SDS, including deficient chondrogenesis, we hypothesise that subglottic stenosis may be a rare symptom of SDS. Otorhinolaryngologist and paediatricians should be aware of the risk of airway pathology in patients with SDS.

Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder with exocrine pancreatic insufficiency, bone marrow failure and skeletal abnormalities. Patients frequently present failure to thrive, susceptibility to infections and short stature. A persistent or intermittent neutropenia occurs in 88-100% of patients. Bone marrow biopsy usually reveals a hypoplastic specimen with varying degrees of hypoplasia and fat infiltration. Some patients may develop myeloblastic syndrome and acute myeloblastic leukemia. The genetic defect in SDS has been identified in 2002. The osteoporosis is increased in patients with SDS, and also, bone malformations are included among the primary characteristics of the syndrome. The severity and location change with age and sexes. The typical characteristics include the following: secondary ossification centers delayed appearance, metaphysis enlargement and irregularity (very common in childhood, particularly in coastal and femur), growth cartilage progressive thinning and irregularity (possibly asymmetric growth), generalized osteopenia with cortical thinning. We describe a clinical case regarding an SDS patient with severe bone abnormalities and treated surgically for corrective osteotomy. The persistent or intermittent neutropenia that characterized this disease and the consequent risk of infection is a contraindication for short stature correction and limbs lengthening.

Deficiency of Sbds in the mouse pancreas leads to features of Shwachman-Diamond syndrome, with loss of zymogen granules

BACKGROUND & AIMS

Shwachman-Diamond syndrome (SDS) is the second leading cause of hereditary exocrine pancreatic dysfunction. More than 90% of patients with SDS have biallelic loss-of-function mutations in the Shwachman-Bodian Diamond syndrome (SBDS) gene, which encodes a factor involved in ribosome function. We investigated whether mutations in Sbds lead to similar pancreatic defects in mice.

METHODS

Pancreas-specific knock-out mice were generated using a floxed Sbds allele and bred with mice carrying a null or disease-associated missense Sbds allele. Cre recombinase, regulated by the pancreatic transcription factor 1a promoter, was used to disrupt Sbds specifically in the pancreas. Models were assessed for pancreatic dysfunction and growth impairment.

RESULTS

Disruption of Sbds in the mouse pancreas was sufficient to recapitulate SDS phenotypes. Pancreata of mice with Sbds mutations had decreased mass, fat infiltration, but general preservation of ductal and endocrine compartments. Pancreatic extracts from mutant mice had defects in formation of the 80S ribosomal complex. The exocrine compartment of mutant mice was hypoplastic and individual acini produced few zymogen granules. The null Sbds allele resulted in an earlier onset of phenotypes as well as endocrine impairment. Mutant mice had reduced serum levels of digestive enzymes and overall growth impairment.

CONCLUSIONS

We developed a mouse model of SDS with pancreatic phenotypes similar to those of the human disease. This model could be used to investigate organ-specific consequences of Sbds-associated ribosomopathy. Sbds genotypes correlated with phenotypes. Defects developed specifically in the pancreata of mice, reducing growth of mice and production of digestive enzymes. SBDS therefore appears to be required for normal pancreatic development and function.

Classification of and risk factors for hematologic complications in a French national cohort of 102 patients with Shwachman-Diamond syndrome

BACKGROUND

Patients with the Shwachman-Diamond syndrome often develop hematologic complications. No risk factors for these complications have so far been identified. The aim of this study was to classify the hematologic complications occurring in patients with Shwachman-Diamond syndrome and to investigate the risk factors for these complications.

DESIGN AND METHODS

One hundred and two patients with Shwachman-Diamond syndrome, with a median follow-up of 11.6 years, were studied. Major hematologic complications were considered in the case of definitive severe cytopenia (i.e. anemia <7 g/dL or thrombocytopenia <20 × 10(9)/L), classified as malignant (myelodysplasia/leukemia) according to the 2008 World Health Organization classification or as non-malignant.

RESULTS

Severe cytopenia was observed in 21 patients and classified as malignant severe cytopenia (n=9), non-malignant severe cytopenia (n=9) and malignant severe cytopenia preceded by non-malignant severe cytopenia (n=3). The 20-year cumulative risk of severe cytopenia was 24.3% (95% confidence interval: 15.3%-38.5%). Young age at first symptoms (<3 months) and low hematologic parameters both at diagnosis of the disease and during the follow-up were associated with severe hematologic complications (P<0.001). Fifteen novel SBDS mutations were identified. Genotype analysis showed no discernible prognostic value. CONCLUSIONS Patients with Shwachman-Diamond syndrome with very early symptoms or cytopenia at diagnosis (even mild anemia or thrombocytopenia) should be considered at a high risk of severe hematologic complications, malignant or non-malignant. Transient severe cytopenia or an indolent cytogenetic clone had no deleterious value.

Draft consensus guidelines for diagnosis and treatment of Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by pancreatic exocrine insufficiency and bone marrow failure, often associated with neurodevelopmental and skeletal abnormalities. Mutations in the SBDS gene have been shown to cause SDS. The purpose of this document is to provide draft guidelines for diagnosis, evaluation of organ and system abnormalities, and treatment of hematologic, pancreatic, dietary, dental, skeletal, and neurodevelopmental complications. New recommendations regarding diagnosis and management are presented, reflecting advances in understanding the genetic basis and clinical manifestations of the disease based on the consensus of experienced clinicians from Canada, Europe, and the United States. Whenever possible, evidence-based conclusions are made, but as with other rare diseases, the data on SDS are often anecdotal. The authors welcome comments from readers.