Chondrodysplasia Punctata 2, X-Linked

Clinical characteristics: The findings in X-linked chondrodysplasia punctata 2 (CDPX2) range from fetal demise with multiple malformations and severe growth retardation to much milder manifestations, including females with no recognizable physical abnormalities. At least 95% of live-born individuals with CDPX2 are female. Characteristic features include growth deficiency; distinctive craniofacial appearance; chondrodysplasia punctata (stippling of the epiphyses of the long bones, vertebrae, trachea, and distal ends of the ribs); often asymmetric rhizomelic shortening of limbs; scoliosis; linear or blotchy scaling ichthyosis in the newborn; later appearance of linear or whorled atrophic patches involving hair follicles (follicular atrophoderma); coarse hair with scarring alopecia; and cataracts.

Diagnosis/testing: The diagnosis of CDPX2 is established in a female proband with: typical clinical findings, increased concentration of 8(9)-cholestenol and 8-dehydrocholesterol in plasma, scales from skin lesions, or cultured lymphoblasts or fibroblasts; and/or a heterozygous pathogenic variant in EBP identified by molecular genetic testing.

The diagnosis of CDPX2 is established in a male proband with: typical clinical findings, increased concentration of 8(9)-cholestenol and 8-dehydrocholesterol in plasma, scales from skin lesions, or cultured lymphoblasts or fibroblasts; and/or a hemizygous pathogenic variant in EBP identified by molecular genetic testing.

Management: Treatment of manifestations: Treatment is symptomatic and individualized. For individuals with typical CDPX2 diagnosed in the newborn period, the following are appropriate: orthopedic management of leg length discrepancy; frequent assessment of kyphoscoliosis; management of respiratory compromise as per pulmonologist; dermatologic management with emollients and keratolytics; sun protection; cataract extraction and correction of vision; standard interventions for hearing loss and hydronephrosis; family support.

Surveillance: Regular orthopedic evaluations to monitor kyphoscoliosis, joint problems, and any leg length discrepancy; follow up with a dermatologist; regular follow up of ophthalmologic abnormalities; audiology evaluations as indicated; monitor hydronephrosis if present.

Agents/circumstances to avoid: Prolonged sun exposure for individuals with ichthyosis, who are at risk of dehydration secondary to overheating. Use of emollients (which are oil based) and direct sun exposure can lead to sunburn.

Genetic counseling: CDPX2 is inherited in an X-linked manner with early gestational male lethality. Women with an EBP germline pathogenic variant have a 50% chance of transmitting the pathogenic variant to each child: EBP pathogenic variants in sons are usually lethal; daughters will have a range of possible phenotypic expression. When the parents are clinically unaffected, the risk to the sibs of a proband appears to be low but greater than that of the general population. If the pathogenic variant cannot be detected in the DNA extracted from the leukocytes of either parent of the proband, three possible explanations are germline mosaicism, somatic mosaicism, or a de novo pathogenic variant in the proband. Prenatal diagnosis for pregnancies at increased risk is possible if the family-specific pathogenic variant is known.