Stippled Epiphyses

Q: Parents of a neonate with rhizomelic chondrodysplasia punctata type 1 ask how long their child will live. What do you tell them?

A: Not what the older textbooks say. In the largest natural history series — 35 systematically studied individuals plus 62 literature cases — 90 per cent reached one year and 50 per cent reached six, with death most often from a respiratory cause; the authors state explicitly that survival is greater than previously reported. That changes the whole conversation: respiratory care determines survival, every infant needs ophthalmology because bilateral cataracts were universal, and the orthopaedic remit becomes long-term surveillance of contractures rather than palliation. Caveat worth stating: the cohort was recruited through support organisations, which under-samples neonatal deaths and biases survival upwards.

Q: During which gestational window does vitamin K antagonist exposure produce chondrodysplasia punctata, and how large is the risk?

A: Classically the sixth to twelfth weeks — but the modern number reframes it. In a prospective cohort of 408 first-trimester vitamin K antagonist pregnancies against 1,642 controls, NOT ONE typical embryopathy occurred. Major malformations overall were increased (7.4 versus 2.3 per cent, OR 2.14), and the effect was almost entirely a function of duration: stopping by five completed gestational weeks gave 2.4 versus 2.3 per cent (OR 1.07 — no excess at all), while continuing beyond seven weeks gave 10.8 per cent (OR 5.18). Spontaneous abortion rose from 17.5 to 38 per cent. So the intervention is early pregnancy recognition and immediate conversion to heparin, and the classic phenotype is rarer than its textbook prominence suggests. Caveat: the drug studied was phenprocoumon, and women who stopped early differ in disease severity from those who could not.

Q: A boy has brachytelephalangic chondrodysplasia punctata. ARSE sequencing is negative. What now?

A: Continue to manage the phenotype. In a prospective series of 29 male probands, ARSE mutations were found in only 58 per cent, and around 40 per cent had neither a detectable mutation nor any identified maternal cause — so the older assumption that unexplained cases are all maternal phenocopies (vitamin K deficiency, autoimmune disease) is not supported. The cervical canal stenosis, hypoplastic odontoid and airway risk are present whatever the genotype, so cervical imaging before anaesthesia and sporting advice proceed unchanged. Note the era caveat: sequencing in 2008–2010 would have missed deep intronic and large-deletion alleles that current methods detect.

Q: An infant has stippling with nasal hypoplasia, no limb shortening and no drug exposure. What maternal investigation is indicated?

A: A maternal autoimmune screen — anti-Ro and anti-La antibodies, looking for lupus or Sjögren syndrome, which reproduce the brachytelephalangic phenotype and in which the mother is sometimes still undiagnosed. Also check maternal vitamin K status and take a malabsorption and hyperemesis history. Add a neonatal ECG for congenital heart block. The association is established from case reports only, so it has no quantified risk — but the tests are cheap and the maternal diagnosis matters in its own right.

Q: A neonate has symmetric rhizomelic shortening, stippled epiphyses and coronal vertebral clefts. Which investigation is most likely to confirm the diagnosis?

A: Plasma phytanic acid and erythrocyte plasmalogens. This combination indicates rhizomelic chondrodysplasia punctata type 1, a peroxisomal disorder of PEX7 — phytanic acid raised, plasmalogens reduced. A sterol profile would be the answer for Conradi–Hünermann, and thyroid function for epiphyseal dysgenesis. Classify by pathway and the test follows.

Q: Which single radiographic feature best separates the brachytelephalangic group from rhizomelic chondrodysplasia punctata?

A: Short distal phalanges with relatively preserved long bone lengths. Rhizomelic disease shortens the humeri and femora severely and symmetrically; the brachytelephalangic phenotypes (CDPX1, vitamin K antagonist embryopathy, maternal vitamin K deficiency, maternal anti-Ro disease) shorten the distal phalanges and hypoplase the midface while stature remains near normal.

Q: A female infant has asymmetric limb shortening, stippling, hemivertebrae and whorled ichthyosis. What is the inheritance pattern?

A: X-linked dominant with male lethality (Conradi–Hünermann–Happle, EBP). The asymmetry of skeletal and cutaneous involvement reflects random X-inactivation. Surviving affected males are usually mosaic or have an additional X chromosome.

Q: A four-year-old is referred with limb length discrepancy and cataracts. Radiographs show no stippling. Does this exclude chondrodysplasia punctata?

A: No. Stippling is a transient sign that resolves as the cartilage ossifies, typically within the first two to three years, sometimes leaving flattened or irregular epiphyses. The neonatal radiographs must be retrieved, and biochemical or genetic testing pursued on clinical grounds.