Ichthyosis: Test and Diagnosis

The diagnosis of ichthyosis is usually made on the basis of physical examination findings. The following laboratory diagnostic procedures are available to determine the form of ichthyosis:

1st-order laboratory parameters-obligatory laboratory tests.

Histology

  • Filaggrin ↓ – histidine-rich cationic protein; produced in the cornification process of the skin; in ichthyosis vulgaris, it is absent or has a defective structure.
  • LEKTI ↓ – protease inhibitor; LEKTI inhibits trypsin-like enzymes of the skin; omits the inhibition → massive inflammation of the skin and reduced horny layer [Comél-Netherton syndrome].

Hair analysis

  • Distinct (distinct) defect of the hair shaft (trichorrhexis invaginata; TI; bamboo hair) [Comél-Netherton syndrome].
  • Trichothiodystrophy: short, brittle hair with lowered sulfur content → indicative of ichthyosis disease.

Electron microscopy

  • Delineation of specific ARCI forms (autosomal recessive congenital ichthyoses, e.g. lamellar ichthyosis or harlequin ichthyosis): TGM1, PNPLA1, NIPAL4

Activity measurements

  • Biopsy (tissue sampling of the skin)
    • To measure enzyme activity in collodion baby and/or ARCI (screening for transglutaminase-1 deficiency).
  • EDTA blood: steroid sulfatase activity measurement in suspected X-linked recessive ichthyosis (XRI) or metabolite screening (DHEAS/dehydroepiandrosterone sulfate).

Molecular genetic testing – for rare and severe forms of ichthyosis.

In the context of hereditary (inherited) forms of ichthyosis, human genetic counseling should be recommended. Thus, prenatal (pre-natal) diagnostics may be considered: