What is erythroderma? It is essentially skin failure and is an extreme state of physiologic and anatomic dysfunction of the barrier and metabolic functions of one of our largest and most important organs. Just like all organs can have failure, so can the skin. It is defined as a scaling and erythematous rash involving ≥90 of body surface area. It is considered a dermatologic emergency when it presents and many patients who acutely are being treated for this benefit from management in a burn unit.
Justin presented a case of a middle-aged caucasian gentleman who presented with erythroderma after failing outpatient treatment and work-up and progression of a diffuse skin rash. He had a history of untreated HCV, IVDU and had been on vancomycin for endocarditis. Here, we go through an approach to differential diagnosis of the causes of erythroderma.
History is key. Erythroderma can be caused by many things and once it gets to the point of skin failure it is hard to diagnose and biopsies can be equivocal. Asking about a history of psoriasis, atopic dermatitis, new medications, and environmental exposures is important. In adults, the most common cause is progression of a pre-existing dermatosis including psoriasis, contact dermatitis, and atopic dermatitis. Drugs are the second most common cause, most implicated are anti-epileptics, anti-microbial, and analgesics. Third is cutaneous T cell lymphoma. .
Physical Exam can also help discern the cause. Certain characteristics of the rash can point you in a direction of the culprit cause. More salmon color is associated with pityriasis rubra pilaris. Deeper red may tie to psoriasis and purple coloring is more seen in cutaneous T cell lymphoma. Look for bullae, which may be a clue for pemphigus vulgaris and bullous pemphigoid. Waxy appearance of palms and soles may hint at pityriasis rubra pilaris.. Look for nail abnormalities such is thickening and pitting, which may clue you into psoriasis.
Looking for eosinophils on the diff can help identify a drug reaction (DRESS).
Here is an Tulane IM Chief original mnemonic to help you remember the different causes of erythroderma: “SCALED RASH”
S – solid organ tumors
C – concealed (aka idiopathic)
A – acute Infection (scabies, dermatophytosis, congenital cutaneous candidiasis, staph scalded skin syndrome, beta hemolytic strep erythroderma)
L – liquid tumors (Cutaneous T-Cell Lymphoma, Sezary syndrome, lymphoma, leukemia)
E – existing dermatoses (Psoriasis, atopic dermatitis, contact dermatitis, pityriasis rubra, lichen planus)
D – drugs (anti-epileptics, antibiotics), Drug Reaction with Systemic Eosinophilia and Systemic Symptoms (DRESS)
R – rejection (aka graft versus host disease)
A – autoimmune (subacute lupus erythematosus, sarcoid, dermatomyositis)
S – saccular (pemphigus vulgaris, bullous pemphigoid)
H – HIV, Histoplasmosis
Several skin biopsies from various locations and at different times are usually needed to make a diagnosis. Once erythroderma is present, biopsies can look similar with inflammation changes and the underlying cause can be difficult to discern. Unfortunately 1/3 of causes are thought to be idiopathic.
Justin’s patient was thought to have eyrthroderma from vancomycin. Vancomycin was stopped and his endocarditis was treated with an alternate regimen. He was given high dose steroids. He was treated with supportive care including fluids and wound care with sauna skin suit to help him retain moisture.
References:
Inamadar AC, Ragunatha S. The rash that becomes an erythroderma. Clin Dermatol. 2019;37(2):88-98. doi:10.1016/j.clindermatol.2018.12.002
Rothe MJ, Bialy TL, Grant-Kels JM. Erythroderma. Dermatol Clin. 2000;18(3):405-415. doi:10.1016/s0733-8635(05)70189-3