CLINICAL DIAGNOSIS OF PSORIASIS
Psoriasis is probably the most common and popular skin disease. Despite its prevalence of 2% worldwide and being a frequent reason for consultation in Dermatology, it can sometimes pose a diagnostic challenge. This is especially true if a methodical (although simple) examination of the patient is not carried out.
This disease occurs in a myriad of forms, although the most typical (called “plaque”) shows very rich semiological characteristics that allow a quick and accurate diagnosis in the vast majority of cases. With the simple observation and palpation of the lesions, it is common to achieve the diagnosis without the practice of complementary tests such as skin biopsy .
WHAT SIGNS TO LOOK FOR WHEN YOU SUSPECT CUTANEOUS PSORIASIS?
1. ON THE SKIN
– Characteristics of the plaques. They usually have very defined borders, even in the palmar, plantar and inverted shapes (in the folds). Around the edge of the lesion it is characteristic, although rare, that a hypochromic light halo may appear, called Woronoff’s halo. This characteristic is more typical of lesions that have already been treated or that present spontaneous regression. The desquamation of the plaques is usually intense, although curiously very easy to detach.
– Scratching the lesion (Brocq’s scratching). When psoriasis is suspected, it is essential to scratch the lesion gently to make it emit the maximum information:
• Spark plug or wax stain sign. When a psoriasis plaque is rubbed, the first thing you notice is that a large amount of flaking is released from it, very accentuated and without any effort.
• Duncan Buckley’s membrane. When the lesion continues to be scratched, after all the flaking has jumped, a layer of very thin translucent tissue appears. This is the last membrane to be detached before bleeding from the lesion appears.
• Auspitz’s sign or hemorrhagic dew. After the removal of Duncan Buckley’s membrane, bleeding appears almost immediately in the form of small scattered droplets at the base of the psoriasis plaque. This sign is pathognomonic for this disease and allows its diagnosis.
– Köebner’s isomorphic phenomenon. There are some skin diseases in which, when a skin trauma occurs (scratch, surgical scar, puncture), new lesions of that disease may appear in the damaged area. This characteristic is not exclusive to psoriasis, but it is characteristic.
– Brunsting’s sign. In plaque psoriasis, it is not uncommon for a lesion to appear that is characteristically located in the intergluteal fold and that often goes unnoticed by the patient himself.
2. IN THE CUTANEOUS APPENDAGES.
When a skin disease is suspected, it is essential to examine the scalp and nails of patients, since they often provide us with relevant information. In the case of psoriasis, this is especially true.
Psoriasis plaques may appear on the scalp , as well as diffuse flaking and redness. It is common for psoriasis plaques to be located in the occipital area or in the retroauricular area. Typically, the hair is preserved and scarring alopecia does not occur no matter how intense the inflammation of the scalp is.
Likewise, in the nails it is common to observe trachyonychia (pitting or the presence of small pits), koilonychia (spoon-shaped disturbance of the nail) and other manifestations of the disease: “oil stains”, detachment of the nail plate, desquamation and subungual hyperkeratosis.
CONCLUSION
As we have seen, simple exploration through observation and scratching can provide us with a large amount of information that will allow us to make the diagnosis of psoriasis without the need to perform any complementary test.
Despite the fact that technological progress is basic in Medicine and any of its diagnostic and therapeutic disciplines, physical examination continues to be of incalculable value today, being the most profitable medical maneuver due to its extreme simplicity, speed and harmlessness for the patient.
In psoriasis, due to its expressive richness in the skin and adnexa, it is especially useful. This means that the vast majority of cases can be diagnosed in a first meeting without the need to perform any complementary test such as skin biopsy.
ACKNOWLEDGEMENTS
To Dr. Leo Barco for the transfer of high quality images. Consult the online dermatological atlas DERMAFOTO.