Things are not always as they seem, but a good H&P should get you back on track
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A 17-year-old male comes to your ED with increasing, generalized pruritus and the development of diffuse erythema.
He has a long history of moderately severe psoriasis, which resulted in him being hospitalized 1 year earlier (Figures 1 to 3). Due to the dramatic appearance of his skin, he was diagnosed at that time with possible toxic shock syndrome (TSS). However, this was a clinical diagnosis in that there was essentially no fever or other system disfunction and all cultures were negative. Nonetheless, he received anti-staph antimicrobial therapy, and a dermatology consult was obtained. After his psoriasis therapy was intensified, his rash ultimately improved and he was discharged. Prior to that point, he had never seen a dermatologist, and there were concerns about his compliance with therapy.
Due to the severity of his presenting rash, he again was admitted to the hospital. Examination revealed normal vital signs, diffuse erythema and areas of plaques and some pustules (Figures 4 to 6). Multiple cultures were obtained from blood, the raw area of skin and a pustule. His CBC and CMP were normal except for minor renal insufficiency that resolved with IV fluids. His CRP was 150 mg/L. Empiric treatment with a variety of antimicrobial agents was initiated during the first few days of hospitalization, even though he remained afebrile the entire time. The dermatologist was reengaged and performed a skin biopsy, revealing “psoriasiform hyperplasia of the epidermis with spongiosis and intraepidermal and subcorneal collections of neutrophils. There were no eosinophils.” They also described “lakes of pus.”
Summary:
- The patient is a 17-year-old male with poorly managed pustular psoriasis.
- He has a history of a previous hospitalization with clinical (unproven) TSS based on appearance but without fever and no multiorgan involvement or positive cultures.
- Now with a similar presentation, the patient has clusters of pustules and “lakes of pus” on biopsy.
What’s your diagnosis?
A. Staph toxic shock syndrome (STSS)
B. Toxic epidermal necrolysis (TEN)
C. Staph scalded skin syndrome (SSSS)
D. Flair of pustular psoriasis
The answer is D, a flair of previously known pustular psoriasis. The diagnosis was confirmed by biopsy, which finalized the report as being consistent with “pustular psoriasis.” Except for an elevated CRP and mild renal insufficiency, the patient’s lab results were normal. The dermatologist used the term “lakes of pus” in the description of certain areas of the skin (Figure 6), which was apparently taken from the terminology in the pathology report on the biopsy, which is commonly seen in pustular psoriasis. Upon presentation, many experts might advise empiric treatment with anti-staph and anti-strep antimicrobial agents pending culture results and confirmation of the diagnosis. However, after confirming the diagnosis by biopsy and the dermatology consult, as well as the circumstances regarding the first admission, I favored stopping all antimicrobial agents and concentrated on the treatment recommendations by the dermatologist.
The resemblance of the skin findings in STSS, a toxin-mediated disease, can be strikingly similar to that seen in the patient depicted in Figure 7, including clusters of pustules. However, to meet diagnostic criteria of STSS, the patient must have fever, rash and at least three organ systems involved. If there is doubt or concern about a possible staph infection, antimicrobial therapy should obviously be continued.
SSSS, another staph toxin-mediated disease, results from circulating epidermolytic toxin, produced by certain strains of Staphylococcus aureus. This low-molecular-weight protein toxin cleaves the molecular bonds between the cells high in the epidermis, resulting in large, fragile blistering areas of skin (Figure 8) resembling a thermal injury.
TEN, on the other hand, results from a reaction to a medication in the vast majority of patients, with some cases caused by a reaction to certain infections. This causes detachment of the skin at the subepidermal level and death of the keratinocytes, resulting in blisters/bullae that remain intact due to the depth of the injury and thickness of the overlying skin (Figure 9). Due to the depth of the injury to the skin, these patients are best managed in a burn unit or similar facility.
Columnist comments
Dramatic visual findings on a patient can affect the clinical judgment of the diagnostician, leading him or her away from the problem at hand. After reviewing the first admission, it became highly suggestive that the patient was being admitted again for the same problem : poorly controlled severe pustular psoriasis. Neither admission could fulfill the diagnostic criteria for STSS, and for the reasons noted earlier , he did not fit TEN or SSSS either. I had never seen a case of severe pustular psoriasis, but I had the advantage of knowing the results of the biopsy soon after I saw the patient, making it fairly easy to rule out a s taph toxin-mediated illness. Diagnostic criteria for complex disorders and syndromes are established to help avoid getting stuck on the wrong diagnosis. As such, even without the biopsy results, the diagnosis of STSS or SSSS should be strongly questioned.
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Brien is a member of the Infectious Diseases in Children and Infectious Disease News Editorial Boards, and an adjunct professor of pediatric infectious diseases at McLane Children's Hospital, Baylor Scott & White Health, in Temple, Texas. He can be reached at jhbrien@aol.com.