This lecture, delivered by Dr. Jared Gardner for the College of American Pathologists, focuses on dermatological urgencies and emergencies that general pathologists should be equipped to recognize. The presentation emphasizes critical non-neoplastic conditions that, if misdiagnosed or overlooked, can have severe, even fatal, patient outcomes. Key topics include recognizing acute ischemia in the skin (identified by epidermal and eccrine coil necrosis), the diagnosis of angioinvasive fungal infections (especially in immunosuppressed patients, stressing the unreliability of species identification from histology alone), thrombotic vasculopathy (fibrin thrombi in vessels due to various coagulopathies), and calciphylaxis (calcification around subcutaneous vessels in renal disease patients). The lecture also delves into Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN) and its distinction from Staphylococcal Scalded Skin Syndrome (SSSS) based on histological features rather than clinical presentation alone. Finally, pyoderma gangrenosum, a neutrophilic dermatitis often mistaken for infection, is discussed, highlighting the dangers of surgical debridement (pathergy effect) and the importance of clinical correlation and excluding infection. A central theme is the crucial role of close communication between pathologists and clinical teams, as well as the necessity of adequate biopsy sampling and clinical history for accurate diagnosis.
Dermatological Emergencies for General Pathologists
0:02:08 Introduction to Dermatological Emergencies: Dr. Jared Gardner presents on dermatological urgencies and emergencies, targeting general pathologists who may encounter these conditions in general surgical pathology, frozen sections, or rush biopsies. The lecture draws from a special section in Archives of Pathology focused on dermatopathology for general surgical pathologists, co-authored by Dr. Gardner.
0:05:27 Epidermal Necrosis: A key clue is a uniformly pink, anucleated (dead) epidermis without significant inflammation, indicating a sudden cut-off of blood supply.
0:08:39 Eccrine Coil Necrosis: The eccrine (sweat) glands are highly sensitive to ischemia, so their necrosis is a strong indicator of an acute ischemic event.
0:09:26 Importance: Identifying these signs is critical as many causes of acute ischemia (e.g., thrombotic events, coagulopathy, angioinvasive fungus) are urgent and potentially fatal.
0:10:20 Key Features: Typically seen in immunosuppressed patients, it's a rapidly progressive infection with high mortality. Histologically, it presents with fungal hyphae in vessels, often with thrombus, leading to acute ischemia.
0:10:51 Species Identification Caution: It's unreliable to determine fungal species from histopathology alone. Pathologists should avoid giving a definitive species diagnosis and instead recommend microbial cultures or molecular analysis for accurate identification.
0:12:26 Histological Appearance: Features include skin infarcts, epidermal necrosis, fat necrosis, and hemorrhage, often with minimal inflammation in neutropenic patients. Special stains like PAS and GMS, along with deeper sections, are vital for detection.
0:21:40 Definition & Causes: A generic term for fibrin thrombi filling dermal blood vessels, leading to acute skin ischemia. Causes include inherited/acquired coagulopathies, Disseminated Intravascular Coagulation (DIC), Hemolytic Uremic Syndrome (HUS), and cryoglobulinemia.
0:23:22 Histological Distinction: It's important to differentiate fibrin thrombi (homogenized, dull pink) from simply blood-engorged vessels (showing individual red blood cell outlines). Clinical history is crucial for workup.
0:25:50 Clinical Context: A severe, painful, high-mortality complication, primarily in patients with end-stage renal disease (uremia, dialysis). It begins as purpuric lesions and progresses to necrotic ulcers (eschars).
0:26:36 Histological Hallmark: Calcification around small vessels in the subcutaneous fat and scattered granular calcifications within the fat. Necrosis and thrombi may also be present.
0:30:41 Biopsy Recommendation: Biopsy must adequately sample the subcutaneous fat (wedge excision or telescoping/double punch biopsy) as findings can be focal. Special stains (e.g., von Kossa) and deeper levels can aid detection.
0:33:19 Angioplasia: A helpful secondary clue is the proliferation of new blood vessels in the deep dermis, indicating chronic ischemia and the body's attempt to compensate.
0:36:46 Classification: A spectrum of severe drug-induced reactions, classified by the percentage of body surface area involved (SJS <10%, TEN >30%).
0:38:05 Clinical Clue: Mucosal involvement, especially oral and labial, is a highly characteristic feature. Patients are treated in burn units due to extensive skin loss, fluid/electrolyte imbalance, and infection risk.
0:39:10 Pathological Challenge: Microscopically, SJS/TEN resembles Erythema Multiforme (EM) (vacuolar interface dermatitis with apoptotic keratinocytes). Clinical correlation is essential for differentiation.
0:41:35 Biopsy Processing: Rapidly processed permanent paraffin sections are often preferred over frozen sections for better diagnostic quality.
0:47:39 Etiology: Caused by a circulating exfoliatin toxin from a distant Staphylococcus infection (not in the skin itself).
0:48:47 Histological Distinction: Unlike SJS/TEN, SSSS shows a superficial split in the epidermis, typically at the granular or superior spinous layer (acantholysis), causing the stratum corneum to lift off. There is no vacuolar interface dermatitis.
0:51:24 Nature & Association: A neutrophilic dermatitis often associated with systemic disorders (e.g., inflammatory bowel disease). It causes rapidly progressing, disfiguring ulcers.
0:52:57 Misdiagnosis & Pathergy: Frequently misdiagnosed clinically (e.g., necrotizing fasciitis). Surgical debridement is disastrous, leading to worsening ulcers due to the pathergy effect. Treatment involves steroids or immunosuppressants.
0:54:43 Pathological Features: Classically described as sheets of neutrophils, but chronic lesions often show nonspecific ulcer changes. The key is to exclude infection through special stains and cultures.
0:57:48 Biopsy Recommendation: Biopsy the edge of the ulcer to look for characteristic undermining of the epidermis by inflammatory infiltrate.
1:03:13 Key Takeaway: The entire lecture stresses the critical importance of close communication with clinicians, obtaining thorough clinical history, and adequate biopsy sampling to accurately diagnose these non-neoplastic but potentially life-threatening dermatological conditions.