Clin Med: Bug Bites and Cutaneous Manifestations

Hymenoptera Stings

An inflammatory reaction triggered by the venom of bees, wasps, hornets, or yellow jackets, which contains active peptides, enzymes, and other chemical mediators of pain and inflammation. It presents as immediate burning, localized pain, redness, swelling, and itching that typically resolves in several hours, but can progress to large local reactions greater than ten centimeters peaking at twenty-four to forty-eight hours, blister-like lesions, or acute systemic anaphylaxis

anaphylaxis

Acute, potentially life-threatening systemic allergic rxn likely within minutes to hours

-Will have:

1. Skin/mucosal involvement (hives, flushing, pruritic, swollen lips/tongue) AND respiratory compromise or hypotension or severe GI symptoms

OR

2. Post exposure to known/highly probable allergen: Acute hypotension OR bronchospasm OR laryngeal involvement

Fire Ant Stings

A localized skin reaction caused by swarming, highly aggressive ants that can sting repeatedly, injecting venom that induces localized acute inflammation. It presents as immediate burning or stinging pain, redness, swelling, and itching, which characteristically evolves into classic sterile pustules at the sting sites within twenty-four hours that resolve spontaneously.

Flea Bites

Intensely itchy bites caused by wingless jumping insects associated with dogs, cats, or infested environments. They present as intensely itchy, red, or papulovesicular bumps occurring in clusters predominantly located around the ankles and lower legs, occasionally displaying a visible central puncture mark and potentially leading to hives in hypersensitive children.

Bedbug Bites

Eruptions caused by nocturnal, crevice-dwelling insects that feed on exposed human skin during sleep. They present as intensely itchy, red bumps or welts on exposed areas such as the face, neck, arms, hands, and legs, often grouped together or arranged in classic linear patterns (often referred to as the "breakfast, lunch, and dinner" pattern), and can occasionally cause blister-like reactions.

Black Widow Spider Bite (Latrodectism)

A systemic clinical syndrome triggered by envenomation from a shiny black spider (the female typically displays a red or orange hourglass marking on her abdomen) whose venom contains alpha-latrotoxin, causing massive neurotransmitter release. The bite is often initially unnoticed or mildly painful, but within thirty minutes to several hours, it progresses to local pain, redness, swelling, and severe systemic manifestations including painful muscle cramping, spasms, muscle rigidity, severe abdominal rigidity mimicking an acute abdomen, sweating, high blood pressure, and a rapid heart rate.

Brown Recluse Spider Bite (Loxoscelism)

A localized necrotic injury or systemic clinical syndrome triggered by envenomation from a tan or brown spider (which displays a violin-shaped marking on its cephalothorax) whose venom causes local tissue injury and red blood cell destruction. It presents as an initially painless bite that becomes painful over two to eight hours, showing early local redness, swelling, and central paleness that can evolve into a classic red, white, and blue lesion, progress to dark discoloration, necrosis, and a dry scab, and rarely manifest as systemic loxoscelism with hemolytic anemia, blood in the urine, acute kidney injury, disseminated intravascular coagulation, and shock.

Marine Envenomations (Cnidaria)

A localized inflammatory reaction triggered by contact with marine tentacles (from jellyfish, Portuguese man-of-war, sea anemones, or corals) containing stinging cells called cnidocytes that discharge venom-delivering, barbed nematocysts. It presents with immediate, intense burning or stinging pain and the rapid development of highly characteristic linear or wavy red welts matching the pattern of tentacle contact, with severe stings occasionally leading to blisters, bruising, or systemic toxicity.

Sea Bather's Eruption ("Sea Lice")

An inflammatory skin reaction caused by larval cnidarians (such as the thimble jellyfish) that become trapped beneath swimwear or areas of friction, triggering nematocyst discharge. It presents as intensely itchy, red bumps that develop within hours of ocean exposure, which are characteristically concentrated beneath swimwear and can progress to blisters or small pustules.

Acanthosis Nigricans

A cutaneous disorder most commonly associated with insulin resistance, obesity, type two diabetes mellitus, polycystic ovary syndrome, certain medications (such as systemic corticosteroids or nicotinic acid), or rarely an underlying internal gastric malignancy. It presents as velvety, gray-brown to black hyperpigmented plaques commonly located on the posterior neck, armpits, groin, and skin folds beneath the breasts; sudden onset, rapid progression, or involvement of the palms or soles in an older adult serve as crucial warning signs for internal malignancy.

Pretibial Thyroid Dermopathy (Pretibial Myxedema)

Skin thickening and swelling caused by the autoimmune activation of fibroblasts leading to the excess production of glycosaminoglycans, especially hyaluronic acid. It is seen almost exclusively in patients with Graves disease and thyroid eye disease, presenting on the lower legs as firm, non-pitting, pink, yellow-brown, or purple-red plaques or nodules with a waxy, hardened, "orange peel" appearance.

Erythema Nodosum

An acute inflammatory inflammation of the subcutaneous fat representing a delayed (Type Four) hypersensitivity reaction triggered idiopathically, by infections (most commonly streptococcal throat infections, tuberculosis, histoplasmosis, or coccidioidomycosis), inflammatory diseases (such as sarcoidosis or inflammatory bowel disease), pregnancy, or medications (such as sulfonamides, penicillin, or oral contraceptives). It presents as highly tender, red, non-ulcerating bumps located bilaterally over the front of the shins that fade like a bruise over several weeks and are commonly accompanied by fever, general discomfort, and joint pain.

Pyoderma Gangrenosum

A rare, rapidly progressive inflammatory skin condition that causes painful skin ulcerations, strongly associated with underlying systemic diseases such as inflammatory bowel disease (especially ulcerative colitis), inflammatory arthritis (such as rheumatoid arthritis), or blood cancers. It begins as a small bump, pustule, or nodule that rapidly breaks down into an exquisitely painful ulcer with purple-red, undermined borders and a purulent, necrotic base, demonstrating pathergy where minor skin trauma (such as a biopsy or needle stick) dramatically worsens the lesion.

Sweet's Syndrome (Acute Febrile Neutrophilic Dermatosis)

A rare inflammatory disorder characterized on skin biopsy by a dense neutrophilic accumulation in the dermis without blood vessel inflammation, associated with acute myeloid leukemia, blood cancers, autoimmune diseases, recent infections, or medications. It presents with fever, elevated white blood cell counts, elevated inflammatory markers, and a sudden onset of painful, tender, raised, and sharply defined red bumps or plaques with a blister-like appearance on the face, neck, and upper extremities.

Cutaneous Vasculitis

An inflammation of blood vessel walls (specifically small vessels) resulting in blood leaking into the surrounding skin, triggered by autoimmune diseases, infections, medications, or blood cancers. It classically presents on the lower extremities as palpable, non-blanching purple-red spots (the hallmark finding), which may occasionally progress to form blisters or ulcers.

Venous Insufficiency

Congestion and tissue changes of the lower extremities driven by chronic high blood pressure in the veins caused by failing vein valves. It presents with swelling in both lower legs, stasis dermatitis (red, scaly, and itchy plaques), brown skin discoloration from iron deposits, skin hardening resulting in an "inverted champagne bottle" appearance, and venous stasis ulcers located classically over the inner ankle.

Sarcoidosis

A multisystem disease characterized tissue-wise by noncaseating granulomas, which most commonly involves the lungs, lymph nodes, eyes, and skin. Cutaneous presentations include skin-colored to red-brown bumps and plaques, infiltration of old scars (old scars becoming raised and active), and lupus pernio (purple-red plaques on the nose, cheeks, and ears strongly associated with chronic systemic disease).

Systemic Lupus Erythematosus

A chronic multisystem autoimmune disease characterized by immune complex deposits, sensitivity to sunlight, and autoantibody production. Cutaneous findings feature a sun-sensitive "butterfly" rash across the cheeks and bridge of the nose that characteristically spares the folds around the nose and mouth, painless mouth or nose sores, round scaly lesions that can heal with scarring, and non-scarring hair loss.

Neurofibromatosis Type I (NF1)

An inherited genetic disorder associated with nerve tissue growths, learning disabilities, and bone abnormalities. It presents on the skin with six or more flat, light-brown spots, freckling in the armpits or groin (known as Crowe sign), and multiple soft, fleshy, skin-colored nodules called neurofibromas, alongside brown spots on the colored part of the eye (Lisch nodules) on eye evaluation.

Ehlers-Danlos Syndrome

A group of inherited connective tissue disorders caused by defects in how collagen is made or structured. It presents on the skin as highly stretchable skin with normal snap-back, easy bruising, poor wound healing, and paper-thin, atrophic "cigarette-paper" scars, accompanied by highly flexible joints, frequent joint dislocations, and chronic joint pain

urticaria

a skin condition defined by raised, itchy, red or skin-colored welts (wheals) that can appear anywhere on the body