X-linked Recessive Chondrodysplasia Punctata (CDPX1) is due to a defect in arylsulfatase E (ARSE), located on Xp22.3. Neither the substrate nor function of the encoded warfarin-sensitive arylsulfatase has been identified and molecular analysis remains the only confirmatory diagnostic test. Nevertheless, the majority of patients evaluated have not had identifiable mutations in ARSE, and thus far 23 patients have been reported. The major clinical features in these patients are also present in a group now recognized as phenocopies, due to vitamin K deficiency in early gestation or maternal autoimmune disease. We evaluated the ARSE gene in 11 patients who met clinical criteria for CDPX1. We amplified all exons and intronic flanking sequence from each patient, and investigated suspected deletions or rearrangements by southern analysis. We identified mutations in seven individuals. Of the remainder, three had maternal conditions that further expand the phenocopy group. Thus, this group might represent a proportion of the mutation-negative patients in previous studies. We extracted clinical information from all prior reports over the past decade and show that there are few distinguishing features on examination between these two groups of patients. This study supports heterogeneity for CDPX1-like phenotypes and sorting these out will help to define the biological pathway and genetic contributors.
Brachytelephalangic chondrodysplasia punctata (BCP) describes a group of heterogeneous conditions with overlapping phenotypes. X-linked recessive BCP (CDPX1) (OMIM no. 302950), originally recognized by Sheffield et al., 1 is a panethnic congenital rare disorder that affects males. The most characteristic clinical features are as follows: 2,3 (i) Chondrodysplasia punctata, or stippled epiphyses, observed on X-ray. These minimally involve the ankle and distal phalanges but can also include long bones, vertebrae, hips, costochondral junctions, hyoid bone, and tracheal and bronchial cartilage. Chondrodysplasia punctata can be observed initially in the second trimester of pregnancy by ultrasound but tends to improve or disappear by age 2-3 years. (ii) Brachytelephalangy, or shortening of the distal phalanges. A characteristic finding on X-ray is an inverted triangle appearance of the distal phalanges, with punctata on either side. (iii) Nasomaxillary hypoplasia, referring to absence or hypoplasia of the anterior nasal spine, causing a flat nasal base, reduced nasal tip protrusion, shortened columella, and vertical grooves within the alae nasi. (iv) Proportionate short stature. Another commonly observed characteristic is mixed conductive and sensorineural hearing loss. Most children have normal intellect and life span, but comorbidities can be present, including compression of the cervical spinal cord associated with cervical vertebral abnormalities or stenosis of the upper and lower airways that result from extensive calcifications within the tracheal and bronchial cartilage. 3,4 Intrafamilial differences in disease severity have also been documented. 3 The only known genetic cause of CDPX1 is defects in arylsulfatase E (ARSE). The ARSE gene is located at Xp22.3, within a cluster of contiguous arylsulfatase genes that share high sequence homology, escape X inactivation, and have pseudogenes on the Y chromosome. 5 There are 17 sulfatases in the human genome; all share extensive sequence homology and contain a highly conserved cysteine that undergoes a unique posttranslational modification essential for their catalytic activity. 6-8 ARSE is localized to the Golgi membranes, 9 and its transcript has been identified in multiple tissues. 5 Its protein product is a 589-amino-acid and 60 kD precursor, which is subject Purpose: The only known genetic cause of brachytelephalangic chondrodysplasia punctata is X-linked chondrodysplasia punctata 1 (CDPX1), which results from a deficiency of arylsulfatase E (ARSE). Historically, ARSE mutations have been identified in only 50% of male patients, and it was proposed that the remainder might represent phenocopies due to maternal-fetal vitamin K deficiency and maternal autoimmune diseases. Methods:To further evaluate causes of brachytelephalangic chondrodysplasia punctata, we established a Collaboration Education and Test Translation program for CDPX1 from 2008 to 2010. Of the 29 male probands identified, 17 had ARSE mutations that included 10 novel missense alleles and one single-cod...
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