Numerous bedside diagnostic tests and maneuvers can be employed to help narrow down differential diagnoses, and their use may even obviate the need for biopsy. The clinical signs outlined below are not 100% sensitive, but if present, they can help to clinch specific diagnoses.
FINGERTIPS: PALPATION MANEUVERS THAT CAN HELP CLINCH DIAGNOSES
Palpating lesions, as has been mentioned and outlined previously, will render a wealth of clinical information. Palpating lesions can help to assess their depth and consistency, and can elicit tenderness, all of which can guide diagnosis. There are some further specific palpation maneuvers that can yield diagnostic information:
In patients with suspected SJS/TEN or the pemphigus group of diseases, place sideways pressure, using a thumb, on areas that seem to be necrotic (display tender, red macules), or on the edge of a bulla or erosion. If there is lateral extension of the bulla, or if there is detachment of epidermis from dermis, this is a deemed to be positive and is known as the Nikolsky sign. The Asboe–Hansen sign refers to lateral extension of a bulla after downward pressure on its surface. It is similarly positive in SJS/TEN and the pemphigus group. In any case of suspected tinea versicolor, the typical fine white branny scales may not be immediately evident, and macules may appear smooth. Skin can be stretched laterally over or at the edges of an affected macule by using two thumbs, or a thumb and an index finger. This will allow for the scales to cleave and to become more apparent. Finally, placing firm inward pressure on the sides of a dermatofibroma will cause dimpling. This is called the dimple sign (see Figure 9.55). It will not be positive in older, more atrophic dermatofibromas, or in dermatofibromas that are raised papules or nodules.
Press laterally on the edge of a bulla or on suspected necrotic epidermis in SJS/TEN or pemphigus vulgaris.
Place downward pressure on a bulla in the same conditions.
Place sideways pressure over a suspected macule of tinea versicolor.
Push the edges of a suspected dermatofibroma together.
EMPLOYING A COTTON-TIPPED APPLICATOR
The back of a cotton-tipped applicator can assist in a handful of diagnostic maneuvers; the first is to gently scrape incipient scales over a suspected plaque of psoriasis. This raises the scales, and a diagnostic bright white or silvery color becomes apparent. I call this the modified Auspitz sign. An Auspitz sign describes the bleeding points that eventuate when plaques of psoriasis are firmly scraped with the back of a cotton-tipped applicator. The bleeding points represent tips of the papillary dermis that are unroofed when the thinned rete ridges that are classic of psoriasis are removed. Lighter scraping will not cause bleeding and will make for a more comfortable patient. The second maneuver is to create wheals ...