are small and look as though they were dropped
onto the skin. The lesions have raised edges with
centers that are somewhat depressed and appear
crumpled. Guttate psoriasis is most common on
the trunk, arms, legs, and scalp. The lesions itch,
and may crack and then crust over before HEALING.
Upper respiratory infections such as COLDS or
PHARYNGITIS (notably STREP THROAT) often trigger
outbreaks of guttate psoriasis.
PSORIASIS AND BLOOD DONATION
Some oral medications for psoriasis stay in the
BLOODfor an extended time and have the poten-
tial to cause serious BIRTH DEFECTS. Blood banks
defer people who take or who have taken these
medications from donating blood for periods of
time, depending on the medication. People who
have taken etretinate at any time, which is no
longer available, are permanently deferred
because it remains in the blood indefinitely.Plaque psoriasis The most common form of
psoriasis, plaque psoriasis features erythematous
(reddened) plaques that typically develop on the
knees, elbows, scalp, and trunk. The plaques itch
and sometimes hurt and often crack, bleed, and
crust. Plaque psoriasis also can affect the finger-
nails and toenails, causing pitting, deformation,
discoloration, and separation from the nail bed.
Emotional and physical stress (such as illness or
injury) may initiate outbreaks of plaque psoriasis.
Some people have few outbreaks and other people
have lesions nearly continuously.
Pustular psoriasis The lesions in pustular pso-
riasis look infected but simply contain fluid mixed
with white blood cells, dead skin cells, and other
matter that has the appearance of pus. Adverse
DRUGreactions and topical irritants often trigger
pustular psoriasis.Symptoms and Diagnostic Path
The dermatologist diagnoses psoriasis primarily on
the basis of its symptoms and history, and may
choose to biopsy representative lesions to confirm.
In its early stages, psoriasis may be difficult to dis-
tinguish from DERMATITISand other skin disorders.
The diagnosis becomes more conclusive when
other family members have psoriasis.Treatment Options and Outlook
The extent to which medical treatments can miti-
gate the symptoms of psoriasis depends on the
type and severity of the psoriasis. Unfortunately,
psoriasis responds unpredictably to treatment
methods, with great individual variation. As well,
the lesions may become resistant to specific treat-
ments or medications over time, requiring a shift
in therapeutic approach. This results in a trial-
and-error approach that often frustrates those
who have psoriasis. Dermatologists generally fol-
low a sequential approach of progressively more
intense therapy. Many people with moderate to
severe psoriasis use a combination of therapies to
help control their symptoms. ANTIBIOTIC MEDICA-
TIONSmay be necessary to treat secondary infec-
tions that affect psoriasis lesions.Risk Factors and Preventive Measures
Because psoriasis has genetic predisposition, it is
not possible to prevent its development. Once pso-psoriasis 189PSORIASIS SYMPTOMSType of Psoriasis Characteristic Symptoms
erythrodermic extensive scaly plaques; erythema (redness);INFLAMMATION; intensePRURITUS(itching)
widespreadSKINinvolvement
flexural (inverse) smooth, erythematous lesions
skinfold areas, underarms, groin; pruritus with irritation such as sweating or rubbing
guttate small, droplike lesions; cracks and crusting; mild to moderate pruritus
trunk, arms, legs, scalp
plaque erythematous, scaly lesions; cracks, bleeding, crusting; mild to moderate pruritus
knees, elbows, scalp, trunk, fingernails, toenails
pustular lesions that appear to contain pus; crusting while HEALING; mild to moderate pruritus
trunk, arms, legs