[Biochemical diagnosis of X chromosomal ichthyosis].

Steroid sulfatase (STS) and aryl sulfatase C (ASC) in leucocytes, as well as the electrophoretic mobility of the beta-lipoproteins, were analyzed in 34 patients with autosomal dominant ichthyosis (ADI), 18 patients with X-linked recessive ichthyosis (XRI), 7 patients with congenital nonbullous ichthyosis (CNBI), and 48 controls. The geometric means of both STS and ASC were significantly lower in the group of XRI by a factor of approximately 10. Analysis of ASC showed a clear separation of the whole group of XRI patients opposed to patients with ADI and CNBI and the controls, whereas an overlapping was observed for STS. With one exception, the clinical and biochemical diagnosis (sulfatase) was confirmed by the results of the lipoprotein electrophoresis (LPE). This case, clinically and biochemically diagnosed as XRI, exhibited normal electrophoretic mobility of beta-lipoproteins. We conclude: if the electrophoretic mobility of beta-lipoproteins is enhanced, XRI can be diagnosed; if the LPE is normal, XRI cannot be excluded; in this case, the diagnosis of XRI can be confirmed or rejected by analysis of the microsomal sulfatases.