COACH syndrome

The acronym COACH describes a syndrome associated with:

• C: cerebellar vermis defect (Joubert syndrome)
• O: oligophrenia
• A: ataxia
• C: coloboma
• H: hepatic fibrosis

Epidemiology

COACH syndrome is considered extremely rare.

Associations

The association with infantile polycystic kidney disease or Potter type I is well established. 

Clinical presentation

• delayed psychomotor development
• visual difficulty
• hepatomegaly, elevated levels of liver enzymes (hepatic fibrosis)
• cerebellar ataxia
• dysmorphic features such as hypertelorism and ptosis
• episodic hyperpnea

Pathology

Genetics

Inherited in an autosomal recessive pattern, multiple implicated gene mutations have been identified as causative, including in the MKS3, CC2D2A, and RPGRIP1L genes ⁴.

Radiographic features

Ultrasound

• increased echogenicity of the liver parenchyma, collateral vessels and splenomegaly due to portal hypertension
• increased echogenicity of the kidneys' pyramids
• the sonographic features of eye coloboma include a defect in the retina with an obliquely posterior herniation of the vitreus body; retinal detachment

CT/MRI

• absence or hypoplasia of the vermis: the cerebellar hemispheres appose each other due to the absence of the vermis; the superior cerebellar peduncles are prominent because they have a horizontal course and are well delineated by CSF
• may show evidence of hepatic fibrosis and portal hypertension 
• may show evidence of polycystic kidney disease
• may show chorioretinal colobomas

Treatment and prognosis

The main clinical problem for patients with COACH syndrome is progressive portal hypertension and liver failure. Treatment aims to reduce symptoms and prevent complications.

Differential diagnosis

The lack of oculomotor abnormalities and the episodic hyperpnea distinguish this syndrome from Joubert syndrome.