Horizontal gaze palsy with progressive scoliosis

Horizontal gaze palsy with progressive scoliosis (HGPPS) is an extremely rare autosomal recessive neurological disorder characterized by the absence or severe limitation of horizontal eye movements (horizontal gaze palsy) combined with progressive scoliosis that typically develops during childhood or adolescence. The condition is caused by mutations in the ROBO3 gene on chromosome 11q23-q25, which plays a critical role in axonal guidance during the development of the brainstem and spinal cord. The ROBO3 protein is essential for the proper crossing (decussation) of nerve fibers in the hindbrain, and its dysfunction leads to abnormal uncrossed sensory and motor pathways. Patients with HGPPS are born with a congenital inability to move their eyes horizontally, though vertical eye movements are typically preserved. Compensatory head turning is commonly observed as patients attempt to track objects. The progressive scoliosis, which is the second hallmark feature, usually becomes apparent in infancy or early childhood and can be severe, sometimes requiring surgical intervention. Brain MRI characteristically shows hypoplasia of the pons and medulla, as well as absence of the normal decussation of the superior cerebellar peduncles and pyramidal tracts. Some patients may also exhibit facial nerve palsy or other cranial nerve abnormalities. There is currently no cure or specific treatment for HGPPS. Management is supportive and multidisciplinary, focusing primarily on orthopedic management of scoliosis, which may include bracing or spinal fusion surgery for severe cases. Ophthalmologic follow-up is recommended, though the horizontal gaze palsy itself is generally not amenable to treatment. Prism glasses or other visual aids may be considered to help with functional vision. Genetic counseling is recommended for affected families.

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