MRI of the brain and cervical spinal cord in rhizomelic chondrodysplasia punctata

Background: The classic rhizomelic chondrodysplasia punctata (RCDP) phenotype involves a typical facial appearance, cataracts, skeletal dysplasia causing disproportionate somatic growth failure, microcephaly, and severe psychomotor defects. Biochemical abnormalities include impaired plasmalogen biosynthesis in all forms of RCDP and accumulation of phytanic acid in RCDP type 1. A subset of patients has a milder clinical and biochemical phenotype, with less severe neurologic impairment and an incomplete deficiency in plasmalogens. The impact of plasmalogen deficiency on neurologic function is severe, causing spasticity and mental defects, but its pathomechanism is still unknown. The authors specifically focused on myelination because myelin is rich in ethanolamine plasmalogens. Objective: To define the neuroimaging characteristics of the genetic peroxisomal disorder RCDP. Methods: Twenty-one MR images of the brain and cervical spine of 11 patients were evaluated and correlated with neurologic and biochemical profiles. Results: No abnormalities on MRI were seen in the patients with a mild phenotype of RCDP, whereas delayed myelination, ventricular enlargement and increased subarachnoidal spaces, supratentorial myelin abnormalities, and cerebellar atrophy were observed in patients with the severe phenotype of both RCDP type 1 and 3. The severity of both the MRI abnormalities and the clinical phenotype is correlated with the plasmalogen level. Conclusions: The severe phenotype of rhizomelic chondrodysplasia punctata (RCDP) is accompanied by a specific pattern of both developmental and regressive MRI abnormalities. Plasmalogen levels seem to play an important role in the pathophysiology of CNS abnormalities in RCDP. Increased phytanic acid appears not to be the cause of cerebellar atrophy.