RESEARCH The neurology of rhizome

disorder of peroxisomal metabolism, with an estimated in-cidence of 1:100.000. There are 3 genetic subtypes [1]. ease is characterized by a typical facial appearance, con-genital cataracts, rhizomelia, transient periarticular Bams-Mengerink et al. Orphanet Journal of Rare Diseases 2013, 8:174 http://www.ojrd.com/content/8/1/174ened. In patients with the milder variant, skeletal4Meibergdreef 9, Amsterdam 1105 AZ, The Netherlands Full list of author information is available at the end of the articleRCDP type 1 (OMIM 215100), caused by mutations in the PEX7 gene, is the most common type [2]. RCDP type 2 (OMIM 222765) and 3 (OMIM 600121) are single enzyme deficiencies in the plasmalogen biosynthesis pathway [3]. Clinically the 3 genetic subtypes are indistinguishable; calcifications, arthrogenic contractures, somatic growth impairment and near absence of developmental mile-stones (Figure 1) [5]. Magnetic Resonance Imaging (MRI) of the brain shows both developmental and regressive ab-normalities, including delayed meylination, increased ven-tricular size and subarachnoidal spaces, supratentorial myelin abnormalities, progressive cerebellar atrophy and cervical stenosis [6]. Life expectancy is dramatically short