Atypical skeletal changes in otopalatodigital syndrome type II: Phenotypic overlap among otopalatodigital syndrome type II, boomerang dysplasia, atelosteogenesis type I and type III, and lethal male phenotype of Melnick-Needles syndrome

A case of boomerang dysplasia with a novel causative mutation in filamin B: identification of typical imaging findings on ultrasonography and 3D-CT imaging

Boomerang dysplasia is a rare lethal osteochondrodysplasia characterized by disorganized mineralization of the skeleton, leading to complete nonossification of some limb bones and vertebral elements, and a boomerang-like aspect to some of the long tubular bones. Like many short-limbed skeletal dysplasias with accompanying thoracic hypoplasia, the potential lethality of the phenotype can be difficult to ascertain prenatally. We report a case of boomerang dysplasia prenatally diagnosed by use of ultrasonography and 3D-CT imaging, and identified a novel mutation in the gene encoding the cytoskeletal protein filamin B (FLNB) postmortem. Findings that aided the radiological diagnosis of this condition in utero included absent ossification of two out of three long bones in each limb and elements of the vertebrae and a boomerang-like shape to the ulnae. The identified mutation is the third described for this disorder and is predicted to lead to amino acid substitution in the actin-binding domain of the filamin B molecule.

Bifid tongue, corneal clouding, and Dandy-Walker malformation in a male infant with otopalatodigital syndrome type 2

We report on a male infant with otopalatodigital syndrome type 2 (OPD2) associated with a novel c.514C>G FLNA mutation and unusual clinical features including bifid tongue and congenital corneal clouding. Bifid tongue and congenital corneal clouding have each only been described once previously in a patient with OPD2, and this is the first description of Dandy-Walker malformation (DWM) in OPD2. The presence of these clinical findings in a mutation-confirmed case of OPD2 supports the notion that corneal clouding, bifid tongue, and DWM are part of the constellation of abnormalities caused by mutations in FLNA.

Audiological outcomes after cochlear implantation in a patient with Melnick-Needles syndrome

This is the first report on a successful cochlear implantation in a patient suffering from the Melnick-Needles syndrome (MNS). This case study presents an MNS patient with peri-lingual profound hearing loss, implanted at the age of 38. MNS is a rare X-linked genetic bony dysplasia characterized by skeletal and facial abnormalities. Various soft tissue defects and hearing loss have also been described in MNS; however, this is the first report on bilateral inner ear malformation as a phenotypic feature of MNS. At 15 months after cochlear implantation there was 91% speech identification in open-set monosyllabic CVC test. In noise, the results obtained with the CVC lists were the following: 67% for SNR +15 dB, 52% for SNR +10 dB and 36% for SNR +5 dB. The patient is able to discriminate the differences in all 22 phoneme pairs in the APE phoneme discrimination test. This allows the patient to obtain significant communication ability through the telephone. Conclusions are as follows. 1) Bilateral inner ear malformations and bilateral profound perceptive hearing loss possibly belong to the phenotypic features of MNS. 2) Cochlear implant is potentially a good functional solution for patients suffering from MNS and profound hearing loss. 3) Exceptionally good results on auditory performance have been obtained in this MNS patient with peri-lingual profound hearing loss and almost 36 years duration of deafness.

Otopalatodigital syndrome type 2 in two siblings with a novel filamin A 629G>T mutation: clinical, pathological, and molecular findings

Otopalatodigital syndrome type 2 (OPD2) is an uncommon X-linked condition characterized by dysmorphic facies, a skeletal dysplasia affecting the axial and appendicular skeleton and extraskeletal anomalies including malformations of the brain, heart, genitourinary system, and intestines. Missense mutations of the FLNA gene, which encodes for the protein filamin A, have recently been shown to cause OPD2 and the allelic syndromes otopalatodigital type 1, Melnick-Needles, and frontometaphyseal dysplasia. Collectively these conditions constitute the otopalatodigital spectrum disorders. We report on two sibs affected by OPD2. The diagnosis was achieved at autopsy of a macerated male stillborn with typical external and skeletal findings of OPD2. A subsequent pregnancy was terminated due to ultrasonographic findings resembling those observed in the previous sibling. Histopathological studies revealed osseus sclerosis and do not support the previously reported membranous ossification defect observed in this condition. Mutation analysis demonstrated a novel mutation, 629G>T, in FLNA that had arisen de novo in the mother. This missense mutation predicts the substitution C210F within the second calponin homology domain of the actin-binding domain of filamin A. The identical substitution has been recently identified in an analogous amino-acid position within the actin binding domain of beta-spectrin leading to hereditary spherocytosis. The observation that phenylalanine is normally present in the same position in other proteins (utrophin, dystrophin) but leads to disease when present in filamin A implies that the function and/or structure of these actin binding domains are not entirely equivalent.

A Japanese case of oto-palato-digital syndrome type II: an apparent lack of phenotype-genotype correlation

We report the case of a 12 year-old boy with oto-palato-digital syndrome type II (OPD II). He had various anomalies at birth, including bilateral cataracts, bilateral glaucoma, bilateral severe hearing impairment, congenital heart defect, umbilical herniation, bowed extremities and constrictions of various joints. These clinical features and whole body X-ray findings were compatible with OPD II. However, his ocular disorders such as congenital cataract and glaucoma, and congenital heart defect have never been associated with OPD II as far as we know. His chromosomal analysis revealed normal karyotype, 46,XY. Analysis of the filamin A gene using a standard PCR-direct sequencing method determined a C586T (Arg196Trp) missense mutation in exon 3. Interestingly, the same C586T mutation was reported previously in a patient with OPD I (mild form). Thus, phenotype-genotype correlation of OPD is lacking in those patients. Further clinical and genetic studies are needed to clarify the relationship between phenotypes and genotypes, or to identify other factor(s) that influence the clinical features of this syndrome.

Asphyxiating thoracic dystrophy with facial dysmorphism

Here it is reported a male newborn baby with features of asphyxiating thoracic dystrophy (ATD) with facial dysmorphism. The disproportionate rhizomelic short stature, narrow thorax, long fibulae, wide metaphysis and trident acetabule are consistent with diagnosis of ATD. In addition the baby had facial dysmorphism and broad thumbs and great toes similar to Oto-palato-digital syndrome type II (OPD II). The association of these features with ATD is not reported till date.

A novel 9 bp deletion in the filamin a gene causes an otopalatodigital-spectrum disorder with a variable, intermediate phenotype

We report a four-generation pedigree with six affected females with cranial hyperostosis and various skeletal abnormalities. The phenotype is similar to frontometaphyseal dysplasia, which is part of the otopalatodigital (OPD) spectrum. We identified a novel in-frame deletion in exon 29 of the Filamin A gene (c.4904_4912del, p.R1635_V1637del) encoding rod domain repeat 14 of the protein. The disorder resulted in early lethality in male children. The phenotype of female individuals in this family is variable and rather mild, and bridges the phenotypes of various OPD-spectrum disorders.

Mutations in the gene encoding filamin B disrupt vertebral segmentation, joint formation and skeletogenesis

The filamins are cytoplasmic proteins that regulate the structure and activity of the cytoskeleton by cross-linking actin into three-dimensional networks, linking the cell membrane to the cytoskeleton and serving as scaffolds on which intracellular signaling and protein trafficking pathways are organized (reviewed in refs. 1,2). We identified mutations in the gene encoding filamin B in four human skeletal disorders. We found homozygosity or compound heterozygosity with respect to stop-codon mutations in autosomal recessive spondylocarpotarsal syndrome (SCT, OMIM 272460) and missense mutations in individuals with autosomal dominant Larsen syndrome (OMIM 150250) and the perinatal lethal atelosteogenesis I and III phenotypes (AOI, OMIM 108720; AOIII, OMIM 108721). We found that filamin B is expressed in human growth plate chondrocytes and in the developing vertebral bodies in the mouse. These data indicate an unexpected role in vertebral segmentation, joint formation and endochondral ossification for this ubiquitously expressed cytoskeletal protein.

Phenotypic variation in Melnick-Needles syndrome is not reflected in X inactivation patterns from blood or buccal smear

Melnick-Needles syndrome is a rare putative X-linked dominant bone dysplasia. The patients have short stature, characteristic facial features, and a normal intelligence. The skeletal dysplasia includes S-shaped curvature of tubular bones and sclerosis of the base of the skull. The phenotype of affected individuals varies, even within families. This could be related to X chromosome inactivation. We report here on a very mildly affected mother and her two severely affected daughters with characteristic features of Melnick-Needles syndrome. In addition, the two daughters had very similar pigmented nevi on their back. X chromosome inactivation analysis of blood DNA revealed a skewed X inactivation pattern in all three affected females, with the normal X chromosome as the predominating active X chromosome. The X inactivation pattern was similar in buccal smear and blood DNA in the mother and one of the daughters, whereas the other daughter had a skewed pattern in blood only. X chromosome inactivation in blood and buccal smear DNA therefore does not explain the phenotypic variation in this family. The skewed X chromosome inactivation is in agreement with X-linked inheritance of Melnick-Needles syndrome and suggests a critical role of the Melnick-Needles gene in hematopoietic cell proliferation. Clinical evidence indicates that Melnick-Needles syndrome is allelic to the otopalatodigital syndromes, which have been assigned to Xq26-28. Haplotype analysis of the X chromosomes in this family was in agreement with the localization of the gene for Melnick-Needles syndrome to Xq25-qtel.

Fronto-otopalatodigital osteodysplasia: clinical evidence for a single entity encompassing Melnick-Needles syndrome, otopalatodigital syndrome types 1 and 2, and frontometaphyseal dysplasia

Otopalatodigital syndrome type 2 is an X-linked disorder with minimal expression in carrier females and comprises typical facial anomalies and a generalized bone dysplasia with osteodysplastic changes, brachydactyly, and impaired survival. Recently several other severe malformations were reported in the condition. Melnick-Needles syndrome is an X-linked dominant disorder. Affected males are usually sporadic cases. The exceptional males born to symptomatic women present with a lethal disorder comprising generalized osteodysplasia, deficiency of the first ray, and facial anomalies strikingly similar to those of otopalatodigital syndrome type 2. We report here on three boys with classical, severe, and lethal otopalatodigital type 2 syndrome, and three boys with severe (lethal) Melnick-Needles syndrome, born to affected mothers. We suggest that otopalatodigital type 1 and 2, Melnick-Needles syndrome and frontometaphyseal dysplasia, sharing many clinical manifestations and a similar mode of inheritance, are variants of the same condition: fronto-otopalatodigital osteodysplasia. The relationships to similar syndromes (i.e., Saint-Martin-Gardner-Morrisson syndrome, serpentine fibula syndrome, atelosteogenesis type 3, boomerang dysplasia, and Yunis-Varon syndrome) are discussed.