The IVIC syndrome: a new autosomal dominant complex pleiotropic syndrome with radial ray hypoplasia, hearing impairment, external ophthalmoplegia, and thrombocytopenia

The IVIC syndrome is an autosomal dominant condition affecting mainly the upper limbs. It is described from 19 living members of one family of mostly Caucasoid descent; it came to Venezuela from the Canary Islands 140 years ago. The new mutation appeared six generations ago. It has complete penetrance and wide expressivity for a radial ray defect which may vary from an almost normal thumb to a severely malformed upper limb. When present, the thumb has a long/slender metacarpal and a short distal phalanx, reflected in a typical metacarpophalangeal (MP) pattern profile. Anthropometry reveals delayed growth in the forearms, clavicles, and cranium during adolescence, and permanently in the spine; the maturation of the face, tibiae, and feet is normal. The radial carpal bones are always affected, some being still hypoplastic at advanced ages. Constant palmar dermatoglyphic anomalies are a high a-b ridge count, a distally placed or absent t triradius, and an increased frequency of patterns in the second interdigital area. Extraocular muscles are involved almost always, producing strabismus. Hearing is bilaterally impaired due to a mixed congenital loss, either total or partial. Mild thrombocytopenia and leukocytosis are present before the age of 50 years. There is neither associated ectodermal dysplasia nor heart involvement [except for occasional mild, incomplete right bundle branch block (IRBBB)]; imperforate anus occurs in about 10% of affected persons. The possible pathogenetic relationship to the thalidomide embryopathy and to the Holt-Oram syndrome, among others, is discussed.

Apparent non-penetrance for dystopia in Waardenburg syndrome type I, with some hints on the diagnosis of dystopia canthorum

Two large pedigrees with Waardenburg syndrome type I (W--I), i.e. with dystopia canthorum and blepharophimosis, are described to show both the variable expressivity of dystopia canthorum, which may be confused with non-penetrance of this sign, and the possibility to firmly diagnosis it with the new biometric index W, which differentiates a dystopic from a non-dystopic or a non-apparent dystopic subject, the latter within a defined biometric range. A general discussion of the relative value of blepharophimosis and dystopia canthorum as diagnostic features in W--I is presented, to conclude on the greater value of dystopia canthorum, which can be identified with confidence in more than 96% of carriers. Empirical probabilities are given for dystopia canthorum and blepharophimosis in the general populations, based on data from the world literature, useful for all ethnic groups.

[Irapa type spondylo-epiphyso-metaphyseal osteochondrodysplasia. New type of dwarfism with short spine and metatarsals]

A new dwarfism of a spondyloepiphysometaphyseal dysplasia is described among Venezuelan Indians of the Yukpa (Irapa) tribe. Brachyrrhahia, brachymetatarsia and brachyrhyzomelia in upper limbs and manifestations in proximal epiphyses of femora and distal epiphyses of humera, with moderate to serious impairment of gait, but no significance deviations of the spine, are the main clinical findings. It is a well individualized type among a very heterogeneous and ill-defined group of chondrodystrophies. The inheritance is through an autosomal recessive or less probably an X-linked gene.

Probable loose linkage between the ABO locus and Waardenburg syndrome type I

The possibility of linkage was tested in 3 large kindreds with Waardenburg syndrome type I against the ABO locus. Loose linkage is probably present; the recombination fraction in males, females, and both sexes combined seems to be approximately theta' equals 0.175, theta equals 0.255, and theta', theta equals 0.20, respectively. There are still more informative matings to be studied in those pedigrees, as well as the inminent possibility of determining the phase status in several of them, for the ABO locus and a few other loci.

Genetic heterogeneity in the Waardenburg syndrome

Waardenbury syndrome is divided into three groups: Type I, with dystopia; Type II, and "pseudo-Waardenburg" syndrome, without dystopia; the third has unilateral congenital ptosis. Using Waardenburg's original variables a, b and c, ratios a/b and c/a, Cotterman's L function, newly described indices X and Y and some phenotypic manifestations, a confident neat separation of each type can be obtained. New cases of all types and electron micrographs of the hair pigment anomaly are described.