Ivic Syndrome

IVIC syndrome is a very rare genetic malformation syndrome characterized by upper limb anomalies (radial ray defects, carpal bone fusion), extraocular motor disturbances, and congenital bilateral non-progressive mixed hearing loss.

Epidemiology

Prevalence of IVIC is not known. To date, four affected families from Venezuela, Italy, Hungary, and Turkey (discordant monozygotic twins) have been described.

Clinical description

Asymmetrical upper limbs are a characteristic clinical manifestation. Thumb involvement is the most typical clinical manifestation and can range from absence or hypoplasia to the presence of a triphalangic thumb. Other upper limb anomalies include radial ray defects and carpal bone fusion. Upper limbs may be severely malformed. Extraocular motor disturbances and hearing loss of variable severity have also been reported. Some affected individuals have been reported to have mild thrombocytopenia, leukocytosis, shoulder girdle hypoplasia, cardiac involvement, kidney malrotation, intermediate anorectal malformation (see this term), or rectovaginal fistula. The clinical presentation is highly variable but lower limbs are normal. There have been reports of sudden death.

Etiology

The syndrome has been linked to mutations in the SALL4 gene (20q13.2) encoding a transcription factor involved in the maintenance and self-renewal of embryonic and hematopoietic stem cells. Okihiro syndrome (see this term) is a disorder allelic to IVIC syndrome.

Genetic counseling

IVIC syndrome is inherited in an autosomal dominant manner. Genetic counseling should be offered to affected families, informing them of the 50% risk of offspring inheriting the disease-causing mutation and therefore being affected with the syndrome.