SALL4 mutations in Okihiro syndrome (Duane-radial ray syndrome), acro-renal-ocular syndrome, and related disorders.

Okihiro/Duane-radial ray syndrome (DRRS) is an autosomal dominant condition characterized by radial ray defects and Duane anomaly (a form of strabismus). Other abnormalities reported in this condition are anal, renal, cardiac, ear, and foot malformations, and hearing loss. The disease is the result of a mutation in the SALL4 gene, a human gene related to the developmental regulator spalt (sal) of Drosophila melanogaster. SALL4 mutations may also cause acro-renal-ocular syndrome (AROS), which differs from DRRS by the presence of structural eye anomalies, and phenotypes similar to thalidomide embryopathy and Holt-Oram syndrome (HOS). The SALL4 gene product is a zinc finger protein that is thought to act as a transcription factor. It contains three highly conserved C2H2 double zinc finger domains, which are evenly distributed. A single C2H2 motif is attached to the second domain, and at the amino terminus SALL4 contains a C2HC motif. Seventeen of the 22 SALL4 mutations known to date (five of which are presented here for the first time) are located in exon 2, and five are located in exon 3. These are nonsense mutations, short duplications, and short deletions. All of the mutations lead to preterminal stop codons and are thought to cause the phenotype via haploinsufficiency. This assumption is supported by the detection of six larger deletions involving the whole gene or single exons. This article summarizes the current knowledge about SALL4 defects and associated syndromes, and describes the clinical distinctions with similar phenotypes caused by other gene defects.

A second case of Devriendt syndrome.

We report on a severely retarded female with Robin sequence, short stature, seizures, and a characteristic segmentation of the second metacarpal. A first patient with this rare combination has been published by Devriendt et al. (2000).

Mutations in NSD1 are responsible for Sotos syndrome, but are not a frequent finding in other overgrowth phenotypes.

Recently, deletions encompassing the nuclear receptor binding SET-Domain 1 (NSD1) gene have been described as the major cause of Japanese patients with the Sotos syndrome, whereas point mutations have been identified in the majority of European Sotos syndrome patients. In order to investigate a possible phenotype-genotype correlation and to further define the predictive value of NSD1 mutations, we performed mutational analysis of the NSD1 gene in 20 patients and one familial case with Sotos syndrome, five patients with Weaver syndrome, six patients with unclassified overgrowth/mental retardation, and six patients with macrocephaly/mental retardation. We were able to identify mutations within the NSD1 gene in 18 patients and the familial case with Sotos syndrome (90%). The mutations (six nonsense, eight frame shifts, three splice site, one missense, one in-frame deletion) are expected to result in an impairment of NSD1 function. The best correlation between clinical assessment and molecular results was obtained for the Sotos facial gestalt in conjunction with overgrowth, macrocephaly, and developmental delay. In contrast to the high mutation detection rate in Sotos syndrome, none of the patients with Weaver syndrome, unclassified overgrowth/mental retardation and macrocephaly/mental retardation, harbored NSD1 mutations. We tested for large deletions by FISH analysis but were not able to identify any deletion cases. The results indicate that the great majority of patients with Sotos syndrome are caused by mutations in NSD1. Deletions covering the NSD1 locus were not found in the patients analyzed here.

SHORT syndrome.

We describe a mother and her son with short stature, progeroid facies, Rieger anomaly, teething delay, and mild developmental retardation, particularly speech delay, which are characteristic features of the SHORT syndrome. An additional sign of all described patients is the slight build with lack of subcutaneous fat. Resistance to insulin was suggested by an oral glucose tolerance test in the mother, whereas the test was normal in the index patient at the age of 2 years 2 months. We review the literature and discuss the name-giving symptoms critically. Five familial cases in different generations, equally affected male and female patients and male-to-male transmission point to an autosomal dominant mode of inheritance.

Midline developmental anomalies in Down syndrome.

Infants with Down syndrome are known to have a high frequency of birth defects, particularly cardiac and gastrointestinal defects. Mental retardation of different degrees is common, but accompanying central nervous system malformations are rare. We report a boy born spontaneously in the 37th postconceptional week with multiple malformations: microcephaly, hypertelorism, blepharophimosis, medial cleft palate, micrognathia, omphalocele, and pathologic palmar and plantar creases. Cardial sonography revealed a ventricular septal defect and mild pulmonary stenosis. Cranial magnetic resonance imaging demonstrated a general but infratentorial stressed brain atrophy with widening of the inner and outer cerebrospinal fluid spaces and dysplasia of the corpus callosum. Chromosomal analysis showed a free trisomy 21. The boy had muscular hypotonia and developed severe motor and mental retardation, accompanied by microsomia and generalized epileptic seizures. At age 8 months, he died of sudden nocturnal respiratory and cardiac failure. The peculiarity of this case is the combination of Down syndrome with midline developmental defects (callosal dysplasia, medial cleft palate, omphalocele) accompanied by severe malformative encephalopathy. There are no previous reports of this combination, but there are genetic links between Down syndrome and midline defects concerning the Drosophila single-minded (sim) gene. The expression pattern of the human sim corresponding gene suggests that it might be involved in the pathogenesis of midline defects in Down syndrome.

Spectrum of the acrocallosal syndrome.

Acrocallosal syndrome (ACS) is an autosomal recessive condition, characterized by agenesis of the corpus callosum, pre- and postaxial polydactyly, minor craniofacial anomalies, and, in most patients, severe psychomotor retardation. We here report on three patients with ACS demonstrating a spectrum from mild to severe involvement. Two patients had only mild to moderate mental retardation at the age of 2(1/2) and 4 years, respectively, with surprisingly good speech development. The third patient was severely affected and died at age 7 days because of persistent apnea. All three patients had agenesis of the corpus callosum, and large intracranial cysts, which in the third case was confirmed as a large arachnoid cyst at autopsy. Cranial cysts were also seen in 10/34 published cases of ACS. Thus, intracerebral cysts are a common finding in ACS and may serve in differentiating ACS from Greig cephalopolysyndactyly syndrome.