Gene Expression-Based Molecular Test as Diagnostic Aid for the Differential Diagnosis of Psoriasis and Eczema in Formalin-Fixed and Paraffin-Embedded Tissue, Microbiopsies, and Tape Strips.

Highly effective targeted therapies are available to treat noncommunicable chronic inflammatory skin diseases. In contrast, the exact diagnosis of noncommunicable chronic inflammatory skin diseases is complicated by its complex pathogenesis and clinical and histological overlap. Particularly, the differential diagnosis of psoriasis and eczema can be challenging in some cases, and molecular diagnostic tools need to be developed to support a gold standard diagnosis. The aim of this work was to develop a real-time PCR-based molecular classifier to distinguish psoriasis from eczema in formalin-fixed and paraffin-embedded-fixed skin samples and to evaluate the use of minimally invasive microbiopsies and tape strips for molecular diagnosis. In this study, we present a formalin-fixed and paraffin-embedded-based molecular classifier that determines the probability for psoriasis with a sensitivity/specificity of 92%/100%, respectively, and an area under the curve of 0.97, delivering comparable results to our previous published RNAprotect-based molecular classifier. The psoriasis probability, as well as levels of NOS2 expression, positively correlated with the disease hallmarks of psoriasis and negatively with eczema hallmarks. Furthermore, minimally invasive tape strips and microbiopsies were effectively used to differentiate psoriasis from eczema. In summary, the molecular classifier offers broad usage in pathology laboratories as well as outpatient settings and can support the differential diagnosis of noncommunicable chronic inflammatory skin diseases on a molecular level using formalin-fixed and paraffin-embedded tissue, microbiopsies, and tape strips.

[In case of pruritus, always consider scabies!]. / Vid klåda, tänk alltid på skabb!

In case of pruritus, always consider scabies! Scabies is an itching skin disease caused by the mite Sarcoptes scabiei which affects more than 100 million people worldwide. Regarded as a neglected tropical disease by the WHO, it is a major public health burden in endemic areas. As direct skin-to-skin contact is the main route of transmission family members and sexual partners are often affected. Typical presentation includes a severely pruritic rash with predilection for the extremities and the trunk. Definitive diagnosis relies on microscopic identification of the mites. Future, more efficient, diagnostic methods may include serological testing or PCR for S. scabiei DNA. A benzyl benzoate and disulfiram based lotion, Tenutex, is the treatment of choice in Sweden with topical permethrin or oral ivermectin being used in certain cases. Scabies is an important diagnosis to consider in all patients presenting with pruritus.