Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities. Three subtypes have been described: TRPS I, caused by mutations in the TRPS1 gene on chromosome 8; TRPS II, a microdeletion syndrome affecting the TRPS1 and EXT1 genes; and TRPS III, a form with severe brachydactyly, due to short metacarpals, and severe short stature, but without exostoses. To investigate whether TRPS III is caused by TRPS1 mutations and to establish a genotype-phenotype correlation in TRPS, we performed extensive mutation analysis and evaluated the height and degree of brachydactyly in patients with TRPS I or TRPS III. We found 35 different mutations in 44 of 51 unrelated patients. The detection rate (86%) indicates that TRPS1 is the major locus for TRPS I and TRPS III. We did not find any mutation in the parents of sporadic patients or in apparently healthy relatives of familial patients, indicating complete penetrance of TRPS1 mutations. Evaluation of skeletal abnormalities of patients with TRPS1 mutations revealed a wide clinical spectrum. The phenotype was variable in unrelated, age- and sex-matched patients with identical mutations, as well as in families. Four of the five missense mutations alter the GATA DNA-binding zinc finger, and six of the seven unrelated patients with these mutations may be classified as having TRPS III. Our data indicate that TRPS III is at the severe end of the TRPS spectrum and that it is most often caused by a specific class of mutations in the TRPS1 gene.

This study provides further evidence of the mutational and clinical spectrum of PTHS and confirms its important role in the differential diagnosis of severe mental retardation.

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From a series of 107 females with Rett syndrome (RTT), we describe the long-term history of ten females with a deletion in the C-terminus of the MECP2 gene. We observed that their disorder profile is clinically recognizable with time and different from other atypical and milder RTT phenotypes. In females with hot spot deletions in the C-terminus, dystonia is present from childhood and results in a serious spine deformation in spite of preventive measures. Their adaptive behavior is surprisingly better preserved and in contrast with the typical decline in motor functioning. The delineation of disorder profiles by long-term clinical observation can teach us about genotype/phenotype relationships and eventually about the effect of epigenetic phenomena on the final phenotype.

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Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over one hundred genes leading to impaired protein or lipid glycosylation. ALG1 encodes a β1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol-lipid linked oligosaccharide intermediate (DLO) required for proper N-linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1-CDG. To date thirteen mutations in eighteen patients from fourteen families have been described with varying degrees of clinical severity. We identified and characterized thirty-nine previously unreported cases of ALG1-CDG from thirty-two families and add twenty-six new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1-deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein-linked xeno-tetrasaccharide biomarker, NeuAc-Gal-GlcNAc2, was seen in all twenty-seven patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.

The phenotype of Gorlin-Goltz syndrome or basal cell nevus syndrome (BCNS, #109400, OMIM), a Mendelian trait due to PTCH mutations has been reported in a few cases of interstitial deletion of chromosome 9q. We present an 11-year-old girl with clinical features consistent with BCNS including bridging of sella turcica, biparietal bossing, downward slanting palpebral fissures, mandible prognathism, pectus excavatum, thumb abnormalities, occult spina bifida at L5-S4, numerous basal cell nevi, and single basal cell carcinoma. Cytogenetic analysis using high-resolution banding techniques and fluorescence in situ hybridization (FISH) revealed interstitial chromosome deletion 9q22.32-q33.2 involving the PTCH gene as a secondary breakage event to a chromosome translocation t(9;17)(q34.1;p11.2)mat. Further FISH studies showed the translocation breakpoint on 9q34.11 maps proximal to ABL, between the BAC clone RP11-88G17 and the LMX1B gene. The latter gene encodes a transcription factor, in which loss of function mutations are responsible for the nail-patella syndrome (NPS, #161200 OMIM). Interestingly, some features of our proband (e.g., bilateral patellar dysplasia and abnormal clavicular shape), as well as her healthy sister who carries the same translocation, are also found in patients with NPS. The chromosome 17p11.2 breakpoint maps in the Smith-Magenis syndrome common deletion region, within two overlapping BAC clones, CTD-2354J3 and RP11-311F12.

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