| Drug
related reactions patterns:
1. Exanthematous drug reaction:
Drugs associated with this
reaction include Ampicillin, amoxyllin, allopurinol, co-trimoxazole,
penicillin, erythromycin, streptomycin, tetracyclin etc. Reaction
develops on the first day or within 3 weeks.
Morphological features:
Erythematous papules and macules. First appears on the trunk or on
areas of trauma or pressure and later spreads to the extremities.
Microscopic features:
Small foci of
spongiosis, vacuolar degeneration in the basal layer, apoptotic
keratinocytes.
Activated lymphocytes, some eosinophils and plasma cells in the
papillary dermis.
2. Halogenoderma (iododerma,
bromoderma, fluroderma):
Caused by ingestion of iodides,bromides
and fluorides.
Clinically, lesions may occur on face, neck , back or extremities as
papules, pustules or vegetating nodules.
Microscopic features:
Pseudoepitheliomatous hyperplasia of the epidermis, intraepidermal
abscesses and in some cases dermal abscesses.
Differential diagnosis:
Chromomycosis and
sporotrichosis.
3. Urticaria:
Acute urticaria in infants may be
caused by furazolidone used in the treatment of diarrhea.
Chronic urticaria may be aggravated by salicylates.
Cold urticaria may follow use of penicillin & griseofulvin.
Clinically, urticaria is characterized by transient pruritic,
edematous, erythematous papules with central clearing.
Microscopic features:
There is mild,
perivascular inflammatory infiltrate (mostly lymphocytes, sometimes
eosinophils and mast cells) and dermal edema. In early case
intravascular and perivascular neutrophils may be noted.
In coexisting angioedema there is edema of subcutaneous tissue and
mucous membrane.
4. Drug induced lichenoid
/ interface patterns:
A: Lichenoid drug eruption
B: Fixed drug eruption
C: Erythema multiforme
D: Lupus erythematosus
A. Lichenoid drug eruption:
Drugs
: Beta-adrenergic blockers, methyldopa,
antimalarial drugs, penicillamine etc.
Clinically the lesions mimick lichen planus. Postinflammatory
pigmentation is more prominent than LP.
Microscopic features:
Focal parakeratosis. Mild basal vacuolar change.Few eosinophils and
sometimes plasma cells are present. Less dense & less band like
inflammatory infiltrate. More pigment incontinence.
Differential diagnosis:
Lichen planus.
B. Fixed drug eruption:
Drugs:
Sulphonamides, Co-trimoxazole, tetracyline, tranquilizer, quinine &
others.
Clinically round or oval erythematous lesion.
Microscopic features:
Prominent vacuolar change. Civatte body formation at and above the
level of basal layer. Inflammation obliterate dermoepidermal junction.
The inflammatory cells in drug eruption extends to mid & upper
epidermis. Few neutrophils are present.
Differential diagnosis:
Erythema multiforme.
C. Erythema multiforme:
Drugs:
Sulfonamides, non-steroidal anti-inflammatory drugs and numerous other
drugs.
Microscopic features
- Divided into epidermal,dermal or mixed types depending on the
histological features. Interphase reaction pattern.Mild to moderate
inflammatory infiltrate at the dermoepidermal junction. Apopotic body
at and above the basal layer. Subepidermal cleft formation in the
vesicular lesions.
Image1
;
Image2
D. Lupus erythematosus:
Subacute:
Drugs:
Thiazide, antihistamine,calcium channel blocker, griseofulvin,
terbinafine etc.
DermAtlas
Systemic:
Drugs:
Procainamide,isoniazid,sulphonamide,
quinidine, penicillamine, phenylbutazone and many others.
Microscopic features:
Features of interphase dermatitis. Superficial & deep dermal
infiltrate. Basal vacuolar change & occasional Civatte bodies.
Epidermal atrophy, dermal edema, superficial mucin, basement membrane
thickening.Follicular plugging. Eosinophils may be present in drug
induced cases.
DermAtlas
5. Toxic epidermal necrolysis:
Image1
;
Image2
Severe form of Erythema
multiforme. Clinically, presents as generalized erythema which
progresses to blistering lesions with peeling of skin.
Classification based on
epidermal detachment:
Steven-Johnson Syndrome-
Less than10% of body surface.
DermAtlas
Steven-Johnson Syndrome/
toxic epidermal necrolysis-
Between 10% - 30% of body surface.
Toxic epidermal
necrolysis-
More than 30%.
Drugs implicated:
Sulphonamide,
anticonvulsants,non-steroidal antinflammatory drugs ,allopurinol,rantidine
etc.
Microscopic features:
Subepidermal bulla. Necrosis of epidermis. Satellite cell necrosis.
Perivascular lymphocytic infiltrate. Necrosis of sweat ducts.
6. Drug related
vesiculobullous & pustular reactions:
Subcorneal pustular
dermatosis:
Cephalosporin etc
Acute
generalized exanthematous pustulosis:
Paracetamol , antimalarial, amoxicillin.
Pemphigus
vulgaris & vegetans:
Ampicillin
Pemphigus
foliaceus & erythematous:
Aspirin etc
Subepidermal bulla :
Cell poor- Pseudoporphyria-
Sulphonamide
Eosinophils- Bullous pemphigoid-
Ampicillin etc
Neutrophils- Linear IgA bullous dermatosis- Frusemide
Scarring- Cicatricial pemphigoid- Azathioprine etc
Necrosis- Drug overdose related- morphine, barbiturate
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