G. Eda Utine

Mutations in the Gene Encoding the RER Protein FKBP65 Cause Autosomal-Recessive Osteogenesis Imperfecta

Osteogenesis imperfecta is a clinically and genetically heterogeneous brittle bone disorder that results from defects in the synthesis, structure, or posttranslational modification of type I procollagen. Dominant forms of OI result from mutations in COL1A1 or COL1A2, which encode the chains of the type I procollagen heterotrimer. The mildest form of OI typically results from diminished synthesis of structurally normal type I procollagen, whereas moderately severe to lethal forms of OI usually result from structural defects in one of the type I procollagen chains. Recessively inherited OI, usually phenotypically severe, has recently been shown to result from defects in the prolyl-3-hydroxylase complex that lead to the absence of a single 3-hydroxyproline at residue 986 of the alpha1(I) triple helical domain. We studied a cohort of five consanguineous Turkish families, originating from the Black Sea region of Turkey, with moderately severe recessively inherited OI and identified a novel locus for OI on chromosome 17. In these families, and in a Mexican-American family, homozygosity for mutations in FKBP10, which encodes FKBP65, a chaperone that participates in type I procollagen folding, was identified. Further, we determined that FKBP10 mutations affect type I procollagen secretion. These findings identify a previously unrecognized mechanism in the pathogenesis of OI.

PORCN mutations in focal dermal hypoplasia: coping with lethality.

The X‐linked dominant trait focal dermal hypoplasia (FDH, Goltz syndrome) is a developmental defect with focal distribution of affected tissues due to a block of Wnt signal transmission from cells carrying a detrimental PORCN mutation on an active X‐chromosome. Molecular characterization of 24 unrelated patients from different ethnic backgrounds revealed 23 different mutations of the PORCN gene in Xp11.23. Three were microdeletions eliminating PORCN and encompassing neighboring genes such as EBP, the gene associated with Conradi‐Hünermann‐Happle syndrome (CDPX2). 12/24 patients carried nonsense mutations resulting in loss of function. In one case a canonical splice acceptor site was mutated, and 8 missense mutations exchanged highly conserved amino acids. FDH patients overcome the consequences of potentially lethal X‐chromosomal mutations by extreme skewing of X‐chromosome inactivation in females, enabling transmission of the trait in families, or by postzygotic mosaicism both in male and female individuals. Molecular characterization of the PORCN mutations in cases diagnosed as Goltz syndrome is particularly relevant for genetic counseling of patients and their families since no functional diagnostic test is available and carriers of the mutation might otherwise be overlooked due to considerable phenotypic variability associated with the mosaic status.

The diagnostic challenge of progressive pseudorheumatoid dysplasia (PPRD): A review of clinical features, radiographic features, and WISP3 mutations in 63 affected individuals

Progressive pseudorheumatoid dysplasia (PPRD) is a genetic, non‐inflammatory arthropathy caused by recessive loss of function mutations in WISP3 (Wnt1‐inducible signaling pathway protein 3; MIM 603400), encoding for a signaling protein. The disease is clinically silent at birth and in infancy. It manifests between the age of 3 and 6 years with joint pain and progressive joint stiffness. Affected children are referred to pediatric rheumatologists and orthopedic surgeons; however, signs of inflammation are absent and anti‐inflammatory treatment is of little help. Bony enlargement at the interphalangeal joints progresses leading to camptodactyly. Spine involvement develops in late childhood and adolescence leading to short trunk with thoracolumbar kyphosis. Adult height is usually below the 3rd percentile. Radiographic signs are relatively mild. Platyspondyly develops in late childhood and can be the first clue to the diagnosis. Enlargement of the phalangeal metaphyses develops subtly and is usually recognizable by 10 years. The femoral heads are large and the acetabulum forms a distinct “lip” overriding the femoral head. There is a progressive narrowing of all articular spaces as articular cartilage is lost. Medical management of PPRD remains symptomatic and relies on pain medication. Hip joint replacement surgery in early adulthood is effective in reducing pain and maintaining mobility and can be recommended. Subsequent knee joint replacement is a further option. Mutation analysis of WISP3 allowed the confirmation of the diagnosis in 63 out of 64 typical cases in our series. Intronic mutations in WISP3 leading to splicing aberrations can be detected only in cDNA from fibroblasts and therefore a skin biopsy is indicated when genomic analysis fails to reveal mutations in individuals with otherwise typical signs and symptoms. In spite of the first symptoms appearing in early childhood, the diagnosis of PPRD is most often made only in the second decade and affected children often receive unnecessary anti‐inflammatory and immunosuppressive treatments. Increasing awareness of PPRD appears to be essential to allow for a timely diagnosis.

A Homozygous Deletion in GRID2 Causes a Human Phenotype With Cerebellar Ataxia and Atrophy

GRID2 is a member of the ionotropic glutamate receptor family of excitatory neurotransmitter receptors. GRID2 encodes the glutamate receptor subunit delta-2, selectively expressed in cerebellar Purkinje cells. The phenotype associated with loss of GRID2 function was described only in mice until now, characterized by different degrees of cerebellar ataxia and usually relatively mild abnormalities of the cerebellum. This work describes for the first time the human phenotype associated with homozygous partial deletion of GRID2 in 3 children in one large consanguineous Turkish family. Homozygous deletion of exons 3 and 4 of GRID2 (94 153 589-94 298 037 bp) in the proband and similarly affected cousins, and heterozygous deletions in parental DNA were shown using Affymetrix® 6.0 single-nucleotide polymorphism array, confirmed by real-time polymerase chain reaction. The phenotype includes nystagmus, hypotonia with marked developmental delay in gross motor skills in early infancy followed by a static encephalopathy course with development of cerebellar ataxia, oculomotor apraxia, and pyramidal tract involvement.

Etiological yield of SNP microarrays in idiopathic intellectual disability.

Intellectual disability (ID) has a prevalence of 3% and is classified according to its severity. An underlying etiology cannot be determined in 75-80% in mild ID, and in 20-50% of severe ID. After it has been shown that copy number variations involving short DNA segments may cause ID, genome-wide SNP microarrays are being used as a tool for detecting submicroscopic copy number changes and uniparental disomy. This study was performed to investigate the presence of copy number changes in patients with ID of unidentified etiology. Affymetrix(®) 6.0 SNP microarray platform was used for analysis of 100 patients and their healthy parents, and data were evaluated using various databases and literature. Etiological diagnoses were made in 12 patients (12%). Homozygous deletion in NRXN1 gene and duplication in IL1RAPL1 gene were detected for the first time. Two separate patients had deletions in FOXP2 and UBE2A genes, respectively, for which only few patients have recently been reported. Interstitial and subtelomeric copy number changes were described in 6 patients, in whom routine cytogenetic tools revealed normal results. In one patient uniparental disomy type of Angelman syndrome was diagnosed. SNP microarrays constitute a screening test able to detect very small genomic changes, with a high etiological yield even in patients already evaluated using traditional cytogenetic tools, offer analysis for uniparental disomy and homozygosity, and thereby are helpful in finding novel disease-causing genes: for these reasons they should be considered as a first-tier genetic screening test in the evaluation of patients with ID and autism.

Pleural fluid PCR method for detection of Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae in pediatric parapneumonic effusions.

Background: Parapneumonic effusions cause significant morbidity and mortality despite current developments in diagnostic and therapeutic approaches. Causative microorganisms may remain unidentified in a significant number of patients by cultures and Gram smears. Polymerase chain reaction (PCR) is a molecular technique for the detection of causative bacteria; however, its efficiency in pleural fluids is less known. Objectives: The present study was performed to compare the efficiency of PCR in the detection of the three most common organisms (Staphylococcus aureus, Streptococcus pneumoniae and Haemophylus influenzae) with conventional methods. Methods: Twenty-eight consecutive patients with parapneumonic pleural effusions were studied. On admission, pleural fluid samples were obtained for Gram staining, routine culture and PCR analysis for S. aureus, S. pneumoniae and H. influenzae. Results: PCR analysis allowed detection of 11 microorganisms in 10 patients (35.7%), whereas pleural fluid cultures detected the etiological agent in only 2 (7.1%). S. pneumoniae was the most frequent agent. Conclusions: Pleural fluid cultures may have low diagnostic yields, partly due to prior antibiotic use. Pleural fluid PCR analysis may improve the etiologic diagnosis in parapneumonic pleural effusions, with technical advances leading to higher yields than obtained in this study.

HERC1 mutations in idiopathic intellectual disability

HERC1 is a member of HERC protein family of ubiquitin ligases and is a negative regulator of the mTOR pathway. It is also a guanine nucleotide exchange factor for ARF and Rab family GTPases. Biallelic mutations in HERC1 were recently shown to cause a human phenotype with overgrowth and intellectual disability as main features. Herein we describe clinical features in another patient with homozygous novel mutation in HERC1. Moderate to severe intellectual disability, hypotonia, macrocephaly, tall stature, and facial features appear as main clinical features of the condition. Kyphoscoliosis and seizures frequently accompany and autistic features might be another feature as recent studies also implicate. HERC1 mutations should be considered in differential diagnosis of severe intellectual disability and behavioural problems, particularly in patients testing negative for fragile X and KANSL1 mutations.

Case Management Guidelines on Neurodevelopmental and Psychosocial Problems of Turner Syndrome

Patients with Turner syndrome are referred to doctors because of neurodevelopmental and behavioural problems such as attention deficiency, hyperactivity, special learning disorders, immaturity, peer problems and social adaptation difficulties during their high school period. However the number of references about these issues is limited. Giving priority to the patients’ other problems like short stature, pubertal problems and absence of follow-up procedures providing multidisciplinary team comprehension can lead to the undermining of such neurodevelopmental and behavioural problems. Such negative effects on the lives of patients with Turner syndrome, as well as on those of family members, may be prevented by providing multidisciplinary yearly diagnosis-prevention-intervention programmes.