Drug Reaction Part 2

Vocabulary practice flashcards generated from lecture notes on drug reactions (Part 2), covering specific drug eruptions, chemotherapeutic mucocutaneous reactions, photosensitivity, hair and mucosal changes, and drug-induced autoimmune/systemic reactions.

Acute Generalized Exanthematous Pustulosis (AGEP)

An acute febrile drug eruption characterized by numerous small, non-follicular sterile pustules arising within a large area of edematous erythema, with more than $90\%$ of cases being drug-induced.

AGEP Onset Latency

The onset of eruption occurs within $< 4\,\text{days}$ after drug administration in individuals with prior sensitization.

Sweet Syndrome (Drug-Induced)

A neutrophilic drug disorder representing less than $5\%$ of all Sweet syndrome cases, characterized by fever, painful erythematous plaques on the face and upper extremities, and dense neutrophilic dermal infiltration without systemic neutrophilia in many drug-induced cases.

Halogenoderma

Cutaneous eruptions (fluoroderma, bromoderma, iododerma) resulting from long-term exposure to fluorides, bromides, or iodides, classically inducing acneiform eruptions and pustules.

Halogenoderma Risk Factor

Renal failure is an important risk factor for the development of halogenoderma due to impaired excretion and slow drug elimination.

Neutrophilic Eccrine Hidradenitis

A chemotherapeutic drug reaction presenting as erythematous painful papules and plaques, histologically characterized by neutrophilic infiltration around and within eccrine glands, occurring $7\text{--}14\,\text{days}$ post-chemotherapy.

Symmetrical Drug-Related Intertriginous and Flexural Exanthem (SDRIFE)

A reaction featuring sharply demarcated symmetrical areas of erythema in the anogenital area and at least one other flexural fold following systemic administration of drugs such as amoxicillin or other $\beta\text{-lactams}$, without systemic signs.

Baboon Syndrome

A clinical presentation of SDRIFE where the predominantly affected areas are the buttocks and upper inner thighs.

Fixed Drug Eruption (FDE)

A drug eruption characterized by one or a few sharply demarcated, round, erythematous to dusky violaceous patches or plaques that recur at the exact same anatomic site upon re-exposure to the offending drug.

Non-Pigmented Variant of FDE

A variant of fixed drug eruption that presents with large edematous erythematous plaques that resolve without leaving residual post-inflammatory hyperpigmentation, commonly caused by pseudoephedrine.

Linear IgA Bullous Dermatosis (LABD)

An autoantibody-mediated subepidermal blistering disease characterized by tense vesicles and bullae arranged in an annular configuration; direct immunofluorescence shows linear deposition of IgA along the basement membrane zone within the lamina lucida. Vancomycin is the most common causative agent.

Drug-Induced Bullous Pemphigoid

A blistering reaction that can develop up to $3\,\text{months}$ after initial drug administration, characterized by a younger age of onset compared to idiopathic BP and lesions that may exhibit an erythema multiforme-like appearance.

Drug-Induced Pemphigus

An autoimmune blistering disorder frequently induced by drugs containing an active thiol group (e.g., penicillamine, captopril), in which perilesional direct immunofluorescence is positive in $90\%$ of cases and circulating anti-Dsg autoantibodies are present in $70\%$.

Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN)

Severe, life-threatening drug-induced mucocutaneous reactions involving extensive epidermal detachment ($< 10\%$ in SJS, $> 30\%$ in TEN) with overall mortality rates of $25\%$ for SJS and $50\%$ for TEN.

Phototoxicity

The most common form of drug-induced photosensitivity, caused by light-triggered reactive oxygen species (ROS) generation; it is dose-dependent and presents immediately as an exaggerated sunburn strictly restricted to sun-exposed areas.

Photo-Onycholysis

A phototoxic reaction resulting in the separation of the nail plate from the nail bed with minimal background nail bed changes.

Pseudoporphyria

A phototoxic drug reaction characterized by skin fragility, erosions, and tense vesicles on the dorsal hands and face in the setting of normal porphyrin levels, most commonly induced by naproxen.

Photoallergy

A delayed cell-mediated hypersensitivity reaction ($\ge 24\,\text{hours}$ latency) triggered when UV light converts a drug into a photoallergen, manifesting as pruritic eczematous or lichenoid lesions in sun-exposed areas.

Anagen Effluvium

Abrupt hair loss occurring within $2\text{--}3\,\text{weeks}$ of exposure to chemotherapeutic agents or toxins due to sudden cessation of mitotic activity in active hair follicles.

Telogen Effluvium

Diffuse non-scarring hair loss occurring $2\text{--}4\,\text{months}$ after drug initiation (e.g., anticoagulants, beta-blockers, retinoids) due to an increased proportion of hair follicles prematurely entering the resting phase.

Flagellate Erythema

A unique, whip-like linear hyperpigmentation pattern of the skin specifically associated with bleomycin chemotherapy.

Radiation Recall

An acute inflammatory skin reaction occurring strictly at sites of previous radiation therapy, triggered by subsequent chemotherapy administration.

Drug-Induced Acneiform Eruption

A monomorphic eruption consisting of papules and pustules on the face and upper trunk without comedones, representing approximately $1\%$ of all drug-induced skin eruptions.

Warfarin-Induced Skin Necrosis

A rare hypercoagulable reaction occurring $2\text{--}5\,\text{days}$ after initiating warfarin therapy due to a rapid drop in protein C activity, presenting as painful erythematous plaques that progress to hemorrhagic bullae and skin necrosis.

Heparin-Induced Cutaneous Necrosis

Skin necrosis caused by antibodies targeting heparin-platelet factor 4 complexes, inducing systemic platelet activation, consumption (thrombocytopenia), and thrombosis at local injection or distant cutaneous sites.

Drug-Induced Systemic Lupus Erythematosus (SLE)

A drug-induced syndrome characterized by fever, malaise, polyarthritis, and serositis with positive anti-histone antibodies in up to $95\%$ of cases, classically caused by hydralazine and procainamide.

Minocycline-Induced SLE

A distinct form of drug-induced lupus that lacks anti-histone antibodies but demonstrates positive ANA, anti-dsDNA, and p-ANCA antibodies.

Drug-Induced Subacute Cutaneous Lupus Erythematosus (SCLE)

A drug-induced lupus subtype featuring persistent annular or psoriasiform skin lesions mainly on the upper trunk and extensor surfaces, strongly associated with anti-Ro/SS-A antibodies.

Pseudolymphomatous Drug Reaction

A benign, insidious lymphoproliferative cutaneous eruption developing months to years after drug initiation (e.g., anticonvulsants), presenting with erythematous-to-violaceous papules, plaques, or nodules accompanied by lymphadenopathy.

Latency Categories of Drug-Induced Psoriasis

Classification based on the onset timeframe following drug exposure: Short latency ($< 4\,\text{weeks}$; e.g., NSAIDs, terbinafine), Intermediate latency ($4\text{--}12\,\text{weeks}$; e.g., antimalarials, ACE inhibitors), and Long latency ($> 12\,\text{weeks}$; e.g., lithium, beta-blockers).