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:
- Chorionic villus sampling – tissue sampling from the fetal (child) portion of the placenta (placenta), 10-12 weeks gestation.
- Amniocentesis (amniocentesis), from the 14th SSW.