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Holoprosencephaly (HPE) is a developmental defect due to a failure of cleavage of the forebrain. The brain malformations are usually associated with facial anomalies. From a series of 258 HPE records involving at least one affected child, 97 cases in 79 families with nonsyndromic and nonchromosomal HPE were selected. The male:female ratio was 0.87. A high degree of familial aggregation was observed in 23/79 families (29%). A segregation analysis performed in the 79 nuclear families led to the conclusion that the transmission of nonsyndromic HPE is compatible with an autosomal dominant mode of inheritance. Under this hypothesis, the penetrance was estimated as 82% for major types (alobar, semilobar, lobar) and 88% when major and minor types (atypical) were included. The proportion of sporadic cases was estimated to be 68%. This genetic model allows a prediction of the recurrence risk after an isolated case of 13% for major types and 14% when minor types are included.

Intracerebral cysts and porencephaly or arachnoid cysts are rarely but are repeatedly reported in orofaciodigital (OFD) syndrome type 1. We report on 2 families in which OFD syndrome type 1 was observed with central nervous system (CNS) malformations and 3 sporadic cases of OFD with CNS defects, most likely representing fresh mutations for OFD 1. In one case, vermis hypoplasia was present; in another, periventricular heterotopiae were noted. We review the literature on CNS anomalies in OFD syndromes and stress the difficulties in genetic counseling and functional prognosis for children of OFD 1 female carriers prenatally diagnosed with a malformation of the brain. As for CNS malformations, renal cystic disease is an often overlooked complication specific to OFD 1. In 1 family, cystic medullary disease was noted in OFD 1 carriers, leading 1 patient to dialysis by age 35 years and the other to severe renal insufficiency by age 28 years. Longitudinal follow-up of OFD 1 carriers should be performed, and renal function should be assessed in those with cysts because the functional prognosis of this developmental anomaly may be worse than usually reported in the literature.

BBB syndrome and G syndrome were originally reported as distinct X-linked disorders. Clinical studies indicated that BBB and G syndromes were likely to represent variant expression of the same disorder, now referred to as "Opitz" GBBB syndrome. Several occurrences of male-to-male transmission in both syndromes led to the hypothesis that GBBB syndrome was a single autosomal dominant, sex influenced disorder, now tentatively mapped to 5p12-13. We report on a large pedigree in which GBBB syndrome appears to cosegregate with a pericentric inversion of the X chromosome inv(X)(p22.3q26). It indicates the possible existence of a true X-linked form of GBBB syndrome, which does not appear phenotypically different from its autosomal counterpart. The gene could map in the vicinity of the breakpoints, in Xp or Xq. The existence of two genes affecting a common pathogenetic pathway could explain the gender-dependent expressivity of GBBB phenotype.

The name opsismodysplasia is proposed for a new chondrodysplasia, which was studied in three patients. Clinically, the condition is recognized at birth on the basis of shortness, short hands, and facial abnormalities with a short nose and a depressed bridge of nose. The most characteristic radiographic signs are: very retarded bone maturation; marked shortness of the bones of the hands and of the feet with concave metaphyses; and thin, lamellar vertebral bodies. The growth cartilage studied in one case showed a wide hypertrophic area containing thick connective tissue septa, irregular provisional calcification, and vascular invasion. Type I collagen was detected in the hypertrophic area by immunohistochemical and microchemical tests. The transmission of opsismodysplasia is probably autosomal recessive.

We report on two sibs with a multiple congenital anomalies/mental retardation (MCA/MR) syndrome who have a first cousin with Möbius anomaly. This may represent a new MCA/MR syndrome.

Two additional pedigrees with familial recurrence of achondroplasia are described. Genetic risk for children of sibs of affected individuals or premutation carriers seems to be low, but it is advisable to monitor at risk pregnancies by midtrimester ultrasonography to diagnose fetal achondroplasia.

The name atelosteogenesis is proposed for a lethal chondrodysplasia characterized by deficient ossification of various bones, notably the humerus, femur, thoracic spine, and hand bones. Clinically, the patients have micromelic dwarfism with incurvated legs, club feet, often dislocation of the elbows, and, rarely, a cleft palate. The most characteristic radiographic signs are incomplete ossification of the vertebral bodies with coronal clefts of the lumbar and hypoplasia of the upper thoracic vertebral bodies, a distal hypoplasia and club shape of the humerus and the femur, and the lack of ossification of single phalanges and metacarpals in most patients. Histologically, there are clusters of chondrocytes surrounded by fibrous capsules and, more frequently, degeneration zones containing degenerated chondrocytes and copious amounts of metachromatic material in the epiphyses and the basal zone of the growth plate.