DERMATOLOGY. Dr.Pawana Kayastha. FUNCTIONAL ANATOMY,& PHYSIOLOGY OF SKIN. INTEGUMENT : skin( epidermis,dermis ) and associated appendages (sweat glands,sebaceous glands,hairs,nails ). Largest organ in the body.abt. 16% of total body weight. EPIDERMIS : Outermost layer of the integument
A portion of the skin biopsy can be frozen in liquid nitrogen for direct immunofluorescence (IF). This involves visualising antigens that are present in skin by identifying them with fluorescein-labelled antibodies. Similarly, indirect immunofluorescence can identify circulating antibodies in the serum by an additional step of adding the serum to a section of normal skin or other substrate. Immunofluorescence plays a major role in the diagnosis of the autoimmune bullous disorders.
This investigation has played an important role in the diagnosis of some of the rare blistering disorders such as epidermolysisbullosa, although the availability of a range of antibodies to basement membrane zone antigens has in part replaced it.
Phototesting involves exposing skin (often on the back) to a graded series of doses of ultraviolet radiation (UVR) of known wavelength, either on one occasion or repeatedly.
In many photodermatoseserythema will occur at a lower dose of UVR than occurs in the normal population (e.g. drug-induced photosensitivity), or the time course of erythema may be prolonged (as in xerodermapigmentosum). Alternatively, UVR will provoke lesions with the morphology of the underlying photodermatosis, such as may occur in lupus erythematosus or solar urticaria. Diagnostic phototesting is an essential component of the investigation of patients with presumed photosensitive drug reactions and idiopathic photodermatoses such as solar urticaria.