Laboratory Tests for Ichthyosis

Inherited ichthyoses/generalized Mendelian disorders of cornification

Inherited ichthyoses, defined as the generalized form of Mendelian disorders of cornification, are characterized by visible scaling and/or hyperkeratosis of most or all of the skin. This etiologically and phenotypically heterogenous group of conditions is caused by mutations in various different genes important for keratinocyte differentiation and epidermal barrier function. Diagnosing a specific entity is a particular challenge for the nonspecialist presented with the common clinical scaling. For the clinician, this review outlines an algorithmic approach for utilizing diagnostic clues to narrow down the differential diagnosis and to guide further testing and treatment options.

Netherton syndrome: a case report and review of the literature

Netherton syndrome is a rare disorder inherited in an autosomal recessive pattern consisting of ichthyosiform dermatosis, hair shaft abnormalities (trichorrhexis invaginata), and an atopic diathesis. Patients with Netherton syndrome have been found to have a mutation on chromosome 5q32 in a gene named SPINK5 (serine protease inhibitor, Kazal type-5), which encodes an inhibitor of serine proteases called LEKTI. We report a female patient with previously undiagnosed Netherton syndrome who presented to participate in a clinical research trial investigating the benefit of topical tacrolimus 0.03% ointment [Protopic (Fujisawa Pharmaceutical Co. Ltd., Japan)] for the treatment of atopic dermatitis. This patient was confirmed to have a gene mutation in SPINK5. Current literature suggests a relative contraindication for use of topical tacrolimus in patients with Netherton syndrome owing to concern for increased systemic absorption of the drug. Our patient was not able to tolerate topical tacrolimus owing to local irritation, and did not derive any benefit from therapy. Though rare, when evaluating patients with a possible diagnosis of atopic dermatitis, an index of suspicion for Netherton Syndrome must be maintained. History and overall clinical findings, especially in regards to examination of the hair, will aid in diagnosis.

Differential diagnosis and management of very low second trimester maternal serum unconjugated estriol levels, with special emphasis on the diagnosis of X-linked ichthyosis

Incorporation of maternal serum unconjugated estriol into the calculation of risk may increase the yield of serum screening performed during pregnancy for detection of fetal chromosomal and structural anomalies. The differential diagnosis of very low and undetectable levels of unconjugated estriol in maternal serum is discussed, with special emphasis on the prenatal diagnosis of X-linked ichthyosis. The prenatal detection of these findings dictates skilled genetic counseling, targeted sonographic evaluation and examination of fetal karyotype and fetal cDNA for Xp 22.32 with amniotic fluid levels of cortisol, STS, and ASC.