Laboratory tests for ichthyosis.

To summarize briefly, the suggested laboratory tests to diagnose the ichthyoses are listed below. Ichthyosis vulgaris: Skin biopsy if necessary. RXLI: Steroid sulfatase activity or levels of cholesterol sulfate. CIE/LI: Usually no laboratory test indicated. Epidermolytic hyperkeratosis: Skin biopsy; consider keratin gene studies. CHILD syndrome: Usually no laboratory tests needed; radiographic studies. Chondrodysplasia punctata: Usually no laboratory studies needed; radiographic studies. IBIDS: Hair shaft examination, including polarization. KID syndrome: Skin biopsy if necessary. Netherton's syndrome: Hair shaft examination. Neutral lipid storage disease: Check blood smear for vacuoles; skin biopsy (frozen). Refsum's disease: Plasma phytanic acid levels. Sjögren-Larsson syndrome: Assay of FAO activity.