Are laboratory tests helpful in the diagnosis of ichthyoses?

In general, no. However, with recent advancements in genetic testing and microarray analysis, genetic testing is becoming easier and more readily available for this group of disorders. In ichthyosis vulgaris, cultured keratinocytes demonstrate absent or reduced filaggrin keratohyalin granules, and fail to react to antifilaggrin monoclonal antibodies. The defective enzyme in Xlinked ichthyosis, steroid sulfatase, can be assayed in cultured keratinocytes, fibroblasts, leukocytes, or skin scales. Low levels of cholesterol sulfate in blood can be detected by the increased mobility of low-density lipoproteins on serum protein electrophoresis. Female heterozygotes can be detected by Southern blot hybridization from peripheral blood leukocytes. The gene has been mapped to the short arm of the X chromosome (Xp22.3). Several of the rarer ichthyosiform syndromes are also associated with enzyme deficiencies detectable in cell cultures.

Oji V, Traupe H: Ichthyoses: differential diagnosis and molecular genetics, Eur J Dermatol 16(4):349–359, 2006.

Scharschmidt TC, Man MQ, Hatano Y, et al: Filaggrin deficiency confers a paracellular barrier abnormality that reduces inflammatory thresholds to irritants and haptens, J Allergy Clin Immunol 124(3):496–506, 2009.