Dr. Warren Piette discusses an efficient way to diagnose purpura, pointing out four key patterns based on number and distribution of lesions.
Warren W. Piette, MD, Voluntary Attending, Cook County Hospital, and Professor of Dermatology, Rush University Medical Center, Chicago, Illinois
“I’ve had a career-long interest in the workup of purpura. Where do you start? The problem is there are papers on this which talk about going through the differential diagnosis, which is potentially 300 different possibilities. But most of the time, based on the number and distribution of the lesions and their individual morphology, you have three or four most likely diagnoses,” said Warren W. Piette, MD, who presented “Accurate Clinical Diagnosis of Purpura and Vasculitis” at the Practical Symposium 2022 in Beaver Creek, Colorado.
“For me now, when I see a patient with purpura, I start with one of four patterns.”
One is multi-generalized, usually 50 to 100 lesions somewhat randomly distributed on the body, said Dr. Piette, who co-wrote a paper in 1989, coining the term retiform purpura.1
“The second is acral, which can have two subsets. One where it is almost exclusively acral and often includes ears and nose, and a history of cold exposure. Then there is an acral predominance that may also involve the rest of the body.”
The third pattern is something he calls “pauci random,” with relatively few lesions in a somewhat random distribution, said Dr. Piette.
“The fourth and probably the most important to dermatologists is what I call multi-dependent, which is 50 to 100 or more lesions distributed usually in a gravity dependent fashion, typically from the legs down.”
Those four patterns, supplemented by the addition of morphology of individual lesions, are very helpful in the workup of the patient, he said.
The Bigger Picture
The multi-generalized pattern with 100s of lesions across the body generally is caused by a virus or drug, so dermatologists should look for symptoms or a change in medications. Maybe a patient started a new drug, changed the dosage of a drug, or they’ve had recent symptoms that could be compatible with viral disease, said Dr. Piette.
“This is for people who are perhaps uncomfortable but not dying sick. Now, if they’re in the hospital and really sick, you have to think about things like purpura fulminans or catastrophic antiphospholipid antibody syndrome, as well as serious systemic vasculitis, especially anti-neutrophil cytoplasmic autoantibody (ANCA) associated. These often have retiform purpura as one of the types of purpura lesions.”
An acral pattern is likely related to substances causing disease in the blood due to their physical structure change in the cold. That could be cryoglobulins, cryofibrinogen (which are quite common but seldom pathologic), and cold agglutinins. But there is a caveat, said Dr. Piette.
“There is a substance that can induce a syndrome that mimics that… [Levamisole] is used to cut cocaine [and] can lead to lesions on the ears, nose, and elsewhere that are predominately necrotic without obvious early inflammation and sometimes show vasculitis but more often occlusion.”
“I would also point out that the presence of cryoglobulins in the serum can be asymptomatic, terribly symptomatic in the cold, or may be independent of cold and caused by immune-complex formation and immune-complex vasculitis, and the location and morphology of the lesions tell the mechanism.”
According to Dr. Piette, the pauci random pattern doesn’t mean it’s always distributed everywhere. It sometimes can be a bit clustered.
“With pauci random, I think particularly of ANCA vasculitis subgroups and various occlusion syndromes.”
And regarding the fourth, multi-dependent pattern, if the lesions are not palpable and are 2 mm to 4 mm in size, then it could be simple petechial hemorrhage from lack of platelets or immune-complex disease. The platelet count will help dermatologists distinguish between the two, said Dr. Piette.
“Uniform Palpable lesions in this distribution are almost always immune complex disease.”
“If [the platelet count is] below 20,000, you’re going to worry about platelets first and if it’s above 20,000 you’re going to worry, usually, about immune-complex vasculitis,” he said.
The bottom line in all these examples, according to Dr. Piette: Use the patterns to help make an accurate diagnosis.
Disclosure: Dr. Piette reports no relevant disclosures.
Reference
Piette WW, Stone MS. A cutaneous sign of IgA-associated small dermal vessel leukocytoclastic vasculitis in adults (Henoch-Schönlein purpura). Arch Dermatol. 1989;125(1):53-56.
