Short stature/short limb skeletal dysplasia with severe combined immunodeficiency and bowing of the femora: report of two patients and review

EXTL3 mutations cause skeletal dysplasia, immune deficiency, and developmental delay

Volpi et al. demonstrate that hypomorphic EXTL3 mutations cause abnormalities of heparan sulfate composition, affect signaling in response to growth factors and cytokines, and perturb thymopoiesis, resulting in a novel genetic disease associating skeletal dysplasia, T cell immunodeficiency, and neurodevelopmental delay.

We studied three patients with severe skeletal dysplasia, T cell immunodeficiency, and developmental delay. Whole-exome sequencing revealed homozygous missense mutations affecting exostosin-like 3 (EXTL3), a glycosyltransferase involved in heparan sulfate (HS) biosynthesis. Patient-derived fibroblasts showed abnormal HS composition and altered fibroblast growth factor 2 signaling, which was rescued by overexpression of wild-type EXTL3 cDNA. Interleukin-2–mediated STAT5 phosphorylation in patients’ lymphocytes was markedly reduced. Interbreeding of the extl3-mutant zebrafish (box) with Tg(rag2:green fluorescent protein) transgenic zebrafish revealed defective thymopoiesis, which was rescued by injection of wild-type human EXTL3 RNA. Targeted differentiation of patient-derived induced pluripotent stem cells showed a reduced expansion of lymphohematopoietic progenitor cells and defects of thymic epithelial progenitor cell differentiation. These data identify EXTL3 mutations as a novel cause of severe immune deficiency with skeletal dysplasia and developmental delay and underline a crucial role of HS in thymopoiesis and skeletal and brain development.

ADA-deficient SCID is associated with a specific microenvironment and bone phenotype characterized by RANKL/OPG imbalance and osteoblast insufficiency

Adenosine deaminase (ADA) deficiency is a disorder of the purine metabolism leading to combined immunodeficiency and systemic alterations, including skeletal abnormalities. We report that ADA deficiency in mice causes a specific bone phenotype characterized by alterations of structural properties and impaired mechanical competence. These alterations are the combined result of an imbalanced receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin axis, causing decreased osteoclastogenesis and an intrinsic defect of osteoblast function with subsequent low bone formation. In vitro, osteoblasts lacking ADA displayed an altered transcriptional profile and growth reduction. Furthermore, the bone marrow microenvironment of ADA-deficient mice showed a reduced capacity to support in vitro and in vivo hematopoiesis. Treatment of ADA-deficient neonatal mice with enzyme replacement therapy, bone marrow transplantation, or gene therapy resulted in full recovery of the altered bone parameters. Remarkably, untreated ADA-severe combined immunodeficiency patients showed a similar imbalance in RANKL/osteoprotegerin levels alongside severe growth retardation. Gene therapy with ADA-transduced hematopoietic stem cells increased serum RANKL levels and children's growth. Our results indicate that the ADA metabolism represents a crucial modulatory factor of bone cell activities and remodeling.

[Cartilage-hair hypoplasia]

Cartilage-hair hypoplasia is a rare, autosomal recessive primary immunodeficiency disorder characterized by predominantly T-cell deficiency and metaphyseal chondrodysplasia. The authors summarize current knowledge on molecular genetics, diagnostic characteristics and therapeutic options of this inherited immunodeficiency.

A syndrome of immunodeficiency, autoimmunity, and spondylometaphyseal dysplasia

We treated a 5-year-old boy, in our hospital in south India, who had a history of recurrent respiratory infections, tuberculosis, and severe varicella infection. He was short in build and a radiological examination revealed evidence of spondylometaphyseal dysplasia. Investigation of the immune system was suggestive of compromised cellular immunity. Immunofluorescence and immunoblot assay for antibodies detected underlying multiple disorders such as systemic lupus erythematosus (SLE), autoimmune thrombocytopenia, and juvenile rheumatoid arthritis (JRA). Roifman et al. described a similar syndrome in 2000 and 2003, which was characterized by spondylometaphyseal dyplasia, combined immunodeficiency, and autoimmunity and called it Roifman-Costa syndrome (OMIM 607944). Hence a diagnosis of Roifman-Costa syndrome was made. Ours shall be the first report of such a condition from the Indian subcontinent and hence the communication.

A unique presentation of immuno-osseous dysplasia

The immuno-osseous dysplasias are a rare group of conditions in which short-limbed dwarfism is associated with an immune defect. The best known of these is cartilage hair hypoplasia. However, several reports of other distinct conditions exist, which have been arbitrarily classified on the basis of the immune defect. We present a child with a previously unreported combination of immune and skeletal abnormalities in whom there was an unusual and distinctive skin appearance associated with defective cutaneous elastic fibers. These cutaneous features suggest a unifying link with other immuno-osseous dysplasia but the combination of immune and skeletal defects exposes weaknesses in the current method of classification.

Isolated femoral hypoplasia: an intrauterine differential diagnosis to campomelia

The isolated form of femoral bowing is an important differential diagnosis of campomelia. Therefore, knowledge of isolated anomalies is fundamental for prenatal diagnosis, especially for the differential diagnosis from severe syndromes. Four cases are presented to discuss the differential diagnosis of femoral bowing including a review of the literature. We report four newborn babies with unilateral bowing and shortening of the femur. Three had no further anomaly; one child had additional abnormalities due to coumarin embryopathy. The radiological findings were shortened femora with bowing and varus deformity and cortical thickening on the concave side. All other parts showed normal bone structure. The aetiology of femoral bowing is unknown. Early damage of the cartilaginous model followed by remodelling with thickening on the concave side of the bone similar to the healing of malaligned fractures is suspected. The isolated form of femoral bowing without any other anomalies has to be differentiated from complex and more often severe congenital syndromes such as campomelia. Postpartum radiological examination should be reduced to a single exposure of the affected limb and follow-up should be done by clinical examination.

Congenital aplastic anemia caused by mutations in the SBDS gene: a rare presentation of Shwachman-Diamond syndrome

CLINICAL FINDINGS

Aplastic anemia was diagnosed at birth for a first child from healthy nonconsanguineous parents. The girl had hypoglycemia, which normalized within 2 months. Cow milk allergy was suspected initially, because of skin lesions and diarrhea, followed by severe growth retardation. Clinical and radiologic symptoms gradually became typical for Shwachman-Diamond syndrome. Two common mutations in the SBDS gene (183-184TA-->CT [K62X] and IVS2(258)+2T--> C [C84fs]) were found.

RESULTS

Bone marrow transplantation from a matched unrelated donor was unsuccessful. The genetic information from the deceased patient enabled us to perform prenatal molecular studies during the subsequent pregnancy, successfully predicting a nonaffected child.

CONCLUSIONS

This report describes for the first time the hematologic abnormalities of congenital aplastic anemia and prolonged neonatal hypoglycemia as the presenting symptoms of Shwachman-Diamond syndrome. The finding of common mutations in the presence of these symptoms at birth suggests the lack of a clear phenotype-genotype relationship in this syndrome.

Syndromic immunodeficiencies: genetic syndromes associated with immune abnormalities

In syndromic immunodeficiencies, clinical features not directly associated with the immune defect are prominent. Patients may present with either infectious complications or extra-immune medical issues. In addition to the immunologic abnormality, a wide range of organ systems may be affected. Patients may present with disturbances in skeletal, neurologic, dermatologic, or gastrointestinal function or development. These conditions can be caused by developmental abnormalities, chromosomal aberrations, metabolic disorders, or teratogens. For a number of these conditions, recent advances have resulted in an enhanced understanding of their genetic basis. The finding of immune deficits in a number of defined syndromes with congenital anomalies suggests that an underlying genetic syndrome should be considered in those patients in whom a significant non-immune feature is present.

A novel developmental and immunodeficiency syndrome associated with intrauterine growth retardation and a lack of natural killer cells

OBJECTIVE

To describe a novel syndrome characterized by severe prenatal and postnatal growth failure, mild skeletal and facial abnormalities, and primary immunodeficiency.

DESIGN

The syndrome was observed in 2 sisters. The elder child died of cytomegalovirus infection when she was 18 months old, whereas the younger sister is doing well at 5 years old. We report here clinical, hematologic, and immunologic data for both sisters and compare them with all known inherited disorders with similar clinical or immunologic features.

RESULTS

The immune defect consists of a lack of detectable natural killer cells and small numbers of CD8 alphabeta T cells and polymorphonuclear neutrophils. This is the first report of prenatal and postnatal growth failure associated with mild skeletal and facial abnormalities and primary immunodeficiency.

CONCLUSION

This novel syndrome probably is caused by an autosomal recessive gene defect impairing both intrauterine growth and natural killer cell development. The identification of other kindreds with this syndrome would facilitate the search for its genetic basis.

Kyphomelic dysplasia in two sib fetuses

We present the in utero appearances and postmortem radiographic findings of two sib fetuses, a male and a female, with features suggestive of kyphomelic dysplasia. The fetuses had severe bowing of the long bones, short, flared ribs, platyspondyly, metaphyseal flaring, skin dimpling, with normal external genitalia and karyotypes and a normal pregnancy. They were born to a mother with features of brachydactyly type E. Prenatal ultrasonography of each case showed a normal amount of amniotic fluid, a normal brain, a normal biparietal diameter, symmetrical bowing and shortening of the long bones, and a narrow thorax. Our cases provide support for a familial mode of inheritance for both sexes in kyphomelic dysplasia. Prenatal ultrasound examination can be offered in subsequent pregnancies.

Spondylo-mesomelic-acrodysplasia with joint dislocations and severe combined immunodeficiency: a newly recognised immuno-osseous dysplasia

A newborn girl is described with an association of spondylo-acrodysplasia, mild short limbed dwarfism without significant metaphyseal changes, joint dislocations, and severe immune system dysfunction. This association is distinct from other known immuno-osseous dysplasias, including Schimke dysplasia, ADA deficiency with osseous changes, and Omenn phenotype with short limbed dwarfism.

Malignant B-cell lymphoma in an infant with severe combined immunodeficiency with short-limbed skeletal dysplasia

In an infant with skeletal anomalies and haemolytic disease, intestinal perforation was caused by necrosis of an as yet undetected B-cell lymphoma. Severe combined immunodeficiency with short-limbed skeletal dysplasia was diagnosed. This is the first published report of a patient with this syndrome in combination with haemolytic disease and B-cell-lymphoma.

Immunodeficiency as a component of recognizable syndromes

Immunodeficiency occurs in numerous genetic syndromes. While it is the dominant manifestation in primary immunodeficiencies, immune deficits may also be seen in a variety of other recognizable syndromes. Immunodeficiency has been reported in 64 such conditions, adding to the 45 recognized primary immunodeficiencies. These uncommon syndromes with immune defects can present with: (a) growth deficiency (11 syndromes with disproportionate or proportionate short stature), (b) specific organ system dysfunction (18 with gastrointestinal, dermatologic, or neurologic abnormalities), (c) inborn errors of metabolism (13), (d) miscellaneous anomalies (10), or (e) chromosome anomalies (12). In most of the disorders, only some of the affected patients have immune defects. However, in 27 syndromes, immunodeficiency is a constant finding. We briefly review the clinical manifestations of each syndrome and delineate the specific associated immune defects. In most syndromes, the connection between the immune and other defects is unknown. Recognition of these conditions involving both the immune and other organ systems may facilitate accurate diagnosis and management as well as yield information regarding genes critical for the development of the involved systems.

Association of kyphomelic dysplasia with severe combined immunodeficiency

Kyphomelic dysplasia is a distinct, rare, skeletal dysplasia with short angulated femora, bowing of long bones, short ribs, narrow thorax, and metaphyseal abnormalities. While immune deficiency occurs in other short stature/short-limb skeletal dysplasias and cartilage-hair hypoplasia, it has not been described with kyphomelic dysplasia. We report on an infant with this disorder who had profound humoral and cellular immunologic abnormalities consistent with severe combined immune deficiency (SCID). The infant died at age 2 months of overwhelming cytomegalovirus pneumonia. Kyphomelic dysplasia, as with other short stature/short-limb skeletal dysplasias, can be associated with immune deficiency and immune function should be investigated when this disorder is identified.