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S.L‐M. and F.D. contributed equally.

Funding sources: none.

Conflicts of interest: none declared.

Dear Editor, Conradi–Hünermann–Happle syndrome (CHH, chondrodysplasia punctata type 2, MIM#302960) is an extremely rare X‐linked dominant disorder of cholesterol metabolism, which is usually lethal in male foetuses. Phenotypic expression is variable.1  2 The classical phenotype is associated with skeletal defects (craniofacial anomalies, short stature, shortened asymmetrical limbs associated with epiphyseal stippling), ocular anomalies (congenital cataract, microphthalmia) and skin lesions.

At birth, transient ichthyosiform erythroderma is reported followed by linear ichthyosis on the Blaschko lines (Fig. 1a). Follicular atrophoderma reminiscent of ‘orange peel’ skin occurs in later life (Fig. 1b). Patchy alopecia with coarse hair is usual. Sparse eyelashes and eyebrows are described. In adulthood, skin lesions may be limited to follicular atrophoderma and mild ichthyosis.

CHH is caused by mutations in the emopamil‐binding protein (EBP) gene.2  3 The EBP protein catalyses the conversion of both cholest‐8(9)‐en‐3β‐ol into lathosterol and 8‐dehydrocholesterol (DHC) into 7‐DHC by its Δ(8)‐Δ(7)‐sterol isomerase activity. Abnormally elevated levels of 8‐DHC and cholest‐8(9)‐en‐3β‐ol are associated with CHH. Cholesterol biosynthesis and cholesterol precursors measured by gas chromatography–mass spectrometry (GC‐MS) and EBP analysis are the gold standard for the diagnosis of CHH.4 Based on our clinical observations, we aimed to show the benefit of skin histopathology in the diagnosis of mild cases of CHH.

Issue Section:
Correspondence > Research Letters
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