ARTHROPOD BITES

ARTHROPOD BITES

( = mosquitoes, fleas, flies, chiggers, ticks, wasps, bees, and hornets)

Difficulty to diagnose in children = unaware of the source of the lesions

deny being bitten

CLINICAL MANIFESTATIONS.

Depends on -

species of insect

age group

reactivity of the human host.

injury by various mechanisms,

            mechanical trauma

            invasion of host tissues, as in myiasis;

            contact dermatitis, exposure to cockroach antigens

            granulomatous reaction to retained mouth parts

            transmission of systemic disease

            injection of irritant cytotoxic or pharmacologically active substances, such as hyaluronidase, proteases, peptidases, and phospholipases in sting venom

            induction of anaphylaxis.

reactions to arthropod bites =

When someone is bitten for the first time, no reaction develops.

immediate petechial reaction

After repeated bites, sensitivity develops, producing a pruritic papule

Arthropod bites may occur as solitary, numerous, or profuse lesions,

Delayed hypersensitivity = firm, persistent papules ,become hyperpigmented

Pruritus may be mild or severe, transient or persistent

immediate hypersensitivity reaction = erythematous, evanescent wheal.

Even shock rarely

Complications of arthropod bites – shock and death rarely occurs

Common problems are

            Impetigo

            Folliculitis

            Cellulitis

            lymphangitis,

Papular urticaria occurs in = fleas, mites, bedbugs, gnats, mosquitoes, chiggers, and animal lice.

Individuals with papular urticaria have predominantly transitional lesions in various

TREATMENT.

Alleviation of pruritus by oral antihistamines, cool compresses, and soothing lotions such as calamine,

Topical corticosteroid creams are rarely effective

Topical antihistamines have no role in the treatment

Short course of systemic steroids may be helpful

Insect repellents containing diethyltoluamide (DEET) may give protection against mosquitoes, fleas, flies, chiggers, and ticks

but relatively ineffective against wasps, bees, and hornets.

permethrin-impregnated clothing;

identify and eradicate the etiologic agent.

Pets should be carefully inspected;

Agents that are effective for ridding the home of fleas include lindane, pyrethroids(=Synthetic pyrethrin derivatives that are used as insecticides), and organic thiocyanates.

n sugg� T @�� (y� l pancytopenia

rule out PNH, a Ham's test should be performed.

Bone marrow examination should include both aspiration and a biopsy,

the marrow should be carefully evaluated for cellularity and morphology.

The presence of more than 70% lymphocytes has a poor prognosis.

COMPLICATIONS.

life-threatening bleeding due to thrombocytopenia

infection secondary to protracted neutropenia. =serious bacterial infections , invasive mycoses.

TREATMENT.

supportive care

treat the underlying marrow failure.

antithymocyte globulin (ATG),

corticosteroids

cyclosporine

bone marrow transplantation

hematopoietic colony-stimulating factors

allogeneic bone marrow transplantation = complications of the transplantation, graft versus host disease (which increases with patients' age), and the increased risk for subsequent cancers

androgens, cyclophosphamide, and plasmapheresis.

PROGNOSIS.

severe pancytopenia have an extremely poor prognosis

PANCYTOPENIAS CAUSED BY MARROW REPLACEMENT

before or during malignancy = neuroblastoma or leukemia

consequence of osteoporosis -marble bone disease

myelofibrosis,

myelodysplasia.

collagen vascular disease (e.g., rheumatoid arthritis)

Chromosomal analysis = myelodysplastic syndromes .