IVIC Syndrome

At a glance

A hereditary polymalformative syndrome characterized by hearing impairment, radial ray defects and hand anomalies, internal ophthalmoplegia, thrombocytopenia, and leukocytosis.

Synonyms

Arias Syndrome; Oculo-Oto-Radial Syndrome (OO-RS); Radial Ray Defects, Hearing Impairment, External Ophthalmoplegia, and Thrombocytopenia Syndrome; Oculo-Oto-Radial Syndrome.

History

IVIC is an acronym that stands for Instituto Venezolano de Investiaciones Cientifìcas, where Sergio Arias Cazorla (b. 1933), a Venezuela geneticist, worked. Dr Cazorla was professor of Zoology at the Escuela de Capacitación Forestal de El Junquito 1952 to 1953, and subsequently from 1970 professor of biology at the Universidad Simón Bolívar in Venezuela. From 1975 to 1996 he was professor of human genetics.

Incidence

This syndrome was observed in 19 living descendants of a Caucasoid family that migrated to Venezuela from the Canary Islands in the early 1800s. The disorder could be traced over six generations with complete penetrance. Cases have been described in Italy and Turkish.

Genetic inheritance

Autosomal dominant with complete penetrance and widely variable expression. There is an evidence that IVIC Syndrome is caused by heterozygous mutation in the SALL4 gene on chromosome 20q13. Investigation on monozygotic twins indicated that modification of OORS gene expression must be environmental or epigenetic rather than genetic. It may represent an “iceberg dominant” trait because of the wide range of severity.

Pathophysiology

The gene responsible for this syndrome has variable expressivity, with the most consistent manifestation being a developmental defect of the upper limbs. A mesenchymally based defect could be implicated in the pathogenesis.

Diagnosis and clinical aspects

The radial ray is consistently involved, with degrees of severity ranging from an almost normal thumb to a hypoplastic, triphalangeal thumb attached to the radial border of the second digit. Long and slender metacarpal bones and hypoplastic carpal bones may coexist with proximally fused ulna and radius. One patient had a single forearm bone. Other findings include hearing loss (very frequent), extraocular muscle involvement in the form of strabismus (frequent), mild thrombocytopenia and leukocytosis (less frequent), and imperforated anus (10% of patients). Although very rare, incomplete right bundle branch block has been reported in both children and adults. Clinical examination, upper limb radiographs, audiograms, ophthalmologic examination, and blood cell count contribute to the diagnosis.

Precautions before anesthesia

Obtain blood cell count: possibility of mild thrombocytopenia and/or leukocytosis. Obtain an electrocardiogram (ECG): rare reported cases of incomplete right bundle branch block with occasionally increased QT interval were not associated with any significant cardiovascular dysfunction.

Anesthetic considerations

If present, thrombocytopenia is mild and usually does not necessitate platelet transfusion. Nonetheless, if locoregional anesthesia is considered, an adequate ...