Okihiro syndrome due to 20q13 microdeletion

Okihiro syndrome due to 20q13 microdeletion is a rare genetic condition caused by a chromosomal microdeletion on the long arm of chromosome 20 (20q13) that encompasses the SALL4 gene. This condition is a specific genetic subtype of Okihiro syndrome, also known as Duane-radial ray syndrome (DRRS) or acro-renal-ocular syndrome. It is characterized by the combination of Duane anomaly (a congenital eye movement disorder affecting the ability to move the eye outward, and sometimes inward, due to abnormal innervation of the eye muscles) and upper limb malformations, particularly radial ray defects. Radial ray abnormalities can range from mild thumb hypoplasia or triphalangeal thumbs to complete absence of the thumb or radius. The syndrome can affect multiple body systems beyond the eyes and limbs. Patients may present with renal anomalies (such as kidney malformations or ectopic kidneys), hearing loss (sensorineural or conductive), cardiac defects, and anorectal malformations. The severity and combination of features can vary considerably, even among affected members of the same family. Some individuals may have subtle findings, while others can be more significantly affected. Because this form is caused by a microdeletion rather than a point mutation in SALL4, affected individuals may occasionally exhibit additional features related to the loss of neighboring genes (contiguous gene deletion syndrome). Management is multidisciplinary and symptom-based, involving orthopedic surgery for limb anomalies, ophthalmologic monitoring for Duane anomaly, audiologic evaluation, cardiac assessment, and renal imaging. There is currently no cure or disease-specific therapy; treatment focuses on surgical correction and supportive care tailored to each patient's clinical presentation. Genetic counseling is recommended for affected families.

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