Extended survival in a new case of ter Haar syndrome: further delineation of the syndrome

Mutations in SH3PXD2B cause Borrone dermato-cardio-skeletal syndrome

Borrone Dermato-Cardio-Skeletal (BDCS) syndrome is a severe progressive autosomal recessive disorder characterized by coarse facies, thick skin, acne conglobata, dysmorphic facies, vertebral abnormalities and mitral valve prolapse. We identified a consanguineous kindred with a child clinically diagnosed with BDCS. Linkage analysis of this family (BDCS1) identified five regions homozygous by descent with a maximum LOD score of 1.75. Linkage analysis of the family that originally defined BDCS (BDCS3) identified an overlapping linkage peak at chromosome 5q35.1. Sequence analysis identified two different homozygous mutations in BDCS1 and BDCS3, affecting the gene encoding the protein SH3 and PX domains 2B (SH3PXD2B), which localizes to 5q35.1. Western blot analysis of patient fibroblasts derived from affected individuals in both families demonstrated complete loss of SH3PXD2B. Homozygosity mapping and sequence analysis in a second published BDCS family (BDCS2) excluded SH3PXD2B. SH3PXD2B is required for the formation of functional podosomes, and loss-of-function mutations in SH3PXD2B have recently been shown to underlie 7 of 13 families with Frank-Ter Haar syndrome (FTHS). FTHS and BDCS share some overlapping clinical features; therefore, our results demonstrate that a proportion of BDCS and FTHS cases are allelic. Mutations in other gene(s) functioning in podosome formation and regulation are likely to underlie the SH3PXD2B-mutation-negative BDSC/FTHS patients.

Frank-ter Haar syndrome associated with sagittal craniosynostosis and raised intracranial pressure

BACKGROUND

Frank-ter Haar syndrome is a rare disorder associated with skeletal, cardiac, ocular and craniofacial features including hypertelorism and brachycephaly. The most common underlying genetic defect in Frank-ter Haar syndrome appears to be a mutation in the SH3PXD2B gene on chromosome 5q35.1. Craniosynostosis, or premature fusion of the calvarial sutures, has not previously been described in Frank-ter Haar syndrome.

CASE PRESENTATION

We present a family of three affected siblings born to consanguineous parents with clinical features in keeping with a diagnosis of Frank-ter Haar syndrome. All three siblings have a novel mutation caused by the deletion of exon 13 of the SH3PXD2B gene. Two of the three siblings also have non-scaphocephalic sagittal synostosis associated with raised intracranial pressure.

CONCLUSION

The clinical features of craniosynostosis and raised intracranial pressure in this family with a confirmed diagnosis of Frank-ter Haar syndrome expand the clinical spectrum of the disease. The abnormal cranial proportions in a mouse model of the disease suggests that the association is not coincidental. The possibility of craniosynostosis should be considered in individuals with a suspected diagnosis of Frank-ter Haar syndrome.

Podosomal proteins as causes of human syndromes: a role in craniofacial development?

Podosomes and invadopodia are actin-rich protrusions of the plasma membrane important for matrix degradation and cell migration. Most of the information in this field has been obtained in cancer cells, where the presence of invadopodia has been related to increased invasiveness and metastatic potential. The importance of the related podosome structure in other pathological or physiological processes that require cell invasion is relatively unexplored. Recent evidence indicates that essential components of podosomes are responsible for several human syndromes, some of which are characterized by serious developmental defects involving the craniofacial area, skeleton and heart, and very poor prognosis. Here we will review them and discuss the possible role of podosomes as a player in correct embryo development.

Disruption of the podosome adaptor protein TKS4 (SH3PXD2B) causes the skeletal dysplasia, eye, and cardiac abnormalities of Frank-Ter Haar Syndrome

Frank-Ter Haar syndrome (FTHS), also known as Ter Haar syndrome, is an autosomal-recessive disorder characterized by skeletal, cardiovascular, and eye abnormalities, such as increased intraocular pressure, prominent eyes, and hypertelorism. We have conducted homozygosity mapping on patients representing 12 FTHS families. A locus on chromosome 5q35.1 was identified for which patients from nine families shared homozygosity. For one family, a homozygous deletion mapped exactly to the smallest region of overlapping homozygosity, which contains a single gene, SH3PXD2B. This gene encodes the TKS4 protein, a phox homology (PX) and Src homology 3 (SH3) domain-containing adaptor protein and Src substrate. This protein was recently shown to be involved in the formation of actin-rich membrane protrusions called podosomes or invadopodia, which coordinate pericellular proteolysis with cell migration. Mice lacking Tks4 also showed pronounced skeletal, eye, and cardiac abnormalities and phenocopied the majority of the defects associated with FTHS. These findings establish a role for TKS4 in FTHS and embryonic development. Mutation analysis revealed five different homozygous mutations in SH3PXD2B in seven FTHS families. No SH3PXD2B mutations were detected in six other FTHS families, demonstrating the genetic heterogeneity of this condition. Interestingly however, dermal fibroblasts from one of the individuals without an SH3PXD2B mutation nevertheless expressed lower levels of the TKS4 protein, suggesting a common mechanism underlying disease causation.

Frank-ter Haar syndrome with unusual clinical features

Frank-ter Haar syndrome first recognized by Frank et al. [Y. Frank, M. Ziprkowski, A. Romano, R. Stein, M.B. Katznelson, B. Cohen, R.M. Goodman, Megalocornea associated with multiple skeletal anomalies: a new genetic syndrome?, J. Genet. Hum. 21 (1973) 67-72.] and subsequently confirmed by ter Haar et al. [B. Ter Haar, B. Hamel, J. Hendriks, J. de Jager, Melnick-Needles syndrome: indication for an autosomal recessive form, Am. J. Med. Genet. 13 (1982) 469-477.]. The main clinical features of the syndrome are brachycephaly, wide fontanels, prominent forehead, hypertelorism, prominent eyes, macro cornea with or without glaucoma, full cheeks, small chin, bowing of the long bones, and flexion deformity of the fingers [S.M. Maas, H. Kayserili, J. Lam, M.Y. Apak, R.C. Hennekam, Further delineation of Frank-ter Haar syndrome, Am. J. Med. Genet. 131 (2004) 127-133.]. We report a child with Frank-ter Haar syndrome presenting unusual clinical features. Hypopigmented areas in hair, bilateral adducted thumb, bilateral contractures in elbows and pelvic limb, atrial septal defect have not been described previously in the literature. Our patient also had double-outlet right ventricle.

Mitral valve repair in a patient with Ter Haar Syndrome

Ter Haar Syndrome is one of the most deteriorating disorders defined in the medical era. Up to date only ten patients were reported. We present a living patient with Ter Haar Syndrome who has undergone successful mitral valve repair.

Further delineation of Frank-ter Haar syndrome

The combination of the symptoms megalocornea, multiple skeletal anomalies, and developmental delay was first recognized as a separate entity by Frank et al. and subsequently confirmed by ter Haar et al. The main characteristics are brachycephaly, wide fontanels, prominent forehead, hypertelorism, prominent eyes, macrocornea with or without glaucoma, full cheeks, small chin, bowing of the long bones, and flexion deformity of the fingers. Protruding, simple ears, and prominent coccyx bone can be also regarded as important diagnostic signs. Inheritance most likely is autosomal recessive. Several manifestations such as progressive "coarsening" of the face, hirsutism, gallstones, lingual papillomatosis, and cardiac valve anomalies all point to a possible metabolic basis of the disorder. Here we describe four patients, including three sibs of Turkish descent, with this entity.