Presentation: Neonate with scaly skin and thickened palmar skin

A neonate is born with erythroderma. In addition, the skin is peeling and there are blisters and erosions in areas. The team looking after the patient is concerned about a potential infection, as well as epidermolysis bullosa or ichthyosis.

• Many causes of epidermal differentiation disorders (EDDs) are covered in R165 Ichthyosis and erythokeratoderma. To be eligible for this test, the patient must have at least two features from this list:
  • born with collodion membrane;
  • erythroderma;
  • dark plate-like scales or fine white scaling;
  • ectropium/eclabium; and/or
  • hyperkeratosis.
• There are cases in which other clinical indications should be considered, including a number of rarer causes of ‘collodion baby’:
  • infantile Gaucher disease (R272);
  • ectodermal dysplasias (R163);
  • neutral lipid storage disease with ichthyosis (R166); and
  • Conradi-Hünermann-Happle syndrome (R166).

• Consult the National Genomic Test Directory. From here you can access the rare and inherited disease eligibility criteria for information about individual tests and their associated eligibility criteria. You can also access a spreadsheet of all available tests.
  • For information about how to arrange testing in Wales, Scotland or Northern Ireland, see Genomic testing in the devolved nations.
• For information about the genes that are included on different gene panels, see the NHS Genomic Medicine Service (GMS) Signed Off Panels Resource.
• Decide which of the panels best suits the needs of your patient and/or family.
  • If you suspect EDDs, the correct test to order is R165 Ichthyosis and erythrokeratoderma. This test includes whole exome sequencing (WES) or gene panel sequencing and multiplex ligation-dependent probe amplification (MLPA).
  • If the presentation best fits a palmoplantar EDD, please consider R166 Palmoplantar keratodermas. This clinical indication includes WES or gene panel sequencing and MLPA.
  • If skin fragility is a prominent feature, consider R164 Epidermolysis bullosa and congenital skin fragility. This clinical indication includes WES or gene panel sequencing and MLPA.
  • Rarer causes of ‘collodion baby’ that are not included in R165 require other clinical indications, as outlined above.
• None of the tests outlined above use whole genome sequencing, so you should use your local Genomic Laboratory Hub test order form and consent (record of discussion, or RoD) form.
  • Parental samples may be needed for interpretation of the child’s result. Parental samples can be taken alongside that of the child, and their DNA stored, or can be requested at a later date if needed.
• Most tests are DNA based, and an EDTA sample (typically a purple-topped tube) is required. There are a few tests for which a different type of tube is used; see Samples for genomic testing in rare disease.
• If you are discussing genomics concepts with your patients, you may find it helpful to use the visual communication aids for genomics conversations.
• Information about patient eligibility and test indications was correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

For clinicians

• GeneReviews: Autosomal Recessive Congenital Ichthyosis

References:

• Hernández-Martín Á, Paller AS, Sprecher E and others. ‘A proposal for a new pathogenesis-guided classification for inherited epidermal differentiation disorders‘. British Journal of Dermatology 2025: volume 193, issue 3, pages 544–548. DOI: 10.1093/bjd/ljaf065
• Mazereeuw-Hautier J, Paller AS, Dreyfus I and others. ‘Management of congenital ichthyoses: Guidelines of care: Part one: 2024 update‘. British Journal of Dermatology 2025: volume 193, issue 1, pages 16–27. DOI: 10.1093/bjd/ljaf076

For patients

• British Association of Dermatologists: Ichthyosis
• Ichthyosis Support Group