Page 105 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-20 Rashes

CUTANEOUS AND LABORATORY FINDINGS IN DERMATOMYOSITIS
Head in flexed
position due to
proximal muscle
weakness

DERMATOMYOSITIS (Continued)

the diagnosis is based on the number of the criteria
fulfilled.
Inflammation of the proximal muscle groups has been
well described. Patients often complain of difficulty in
standing from a sitting position or in raising their hands
above their heads. Patients have elevated serum concen-
trations of creatinine kinase, aldolase, and lactate dehy-
drogenase. This is indicative of muscle inflammation
and breakdown. An electromyogram (EMG) can be
used to evaluate the weakness and to differentiate a
nerve origin from a muscle origin. A muscle biopsy,
most commonly of the deltoid muscle, shows active Difficulty in
inflammation on histological examination. swallowing due
This disease can rarely manifest with severe, diffuse to esophageal Gottron’s papules.
interstitial pulmonary fibrosis. Patients with pulmonary Edema and heliotrope discoloration weakness Erythematous, nodular
fibrosis most often test positive for the anti-Jo1 anti- of eyelids; erythematous rash eruption on fingers
body. Anti-Jo1 antibodies have been found to be tar-
geted against the histidyl–transfer RNA synthetase
protein. Overall, it is an uncommon finding except
in dermatomyositis patients with pulmonary disease.
More than 75% of patients with dermatomyositis test Atrophy Immuno-
positive for antinuclear antibodies (ANA). Those with of muscle globulin
malignancy-associated dermatomyositis typically do fibers and deposition
not develop pulmonary fibrosis, and those with pulmo- lymphocyte in blood
nary fibrosis do not develop a malignancy. infiltration vessel of
The malignancy most commonly associated with (muscle muscle
dermatomyositis is ovarian cancer. Many other malig- biopsy) (immuno-
nancies have been seen in association with dermato- fluorescence)
myositis, including breast, lung, lymphoma, and gastric
cancers. Malignancy is seen before the onset of the rash
in about one third of the cases, concurrently with the
rash in one third, and within 2 years after diagnosis of
the dermatomyositis in one third. After the diagnosis
of dermatomyositis, it is imperative to search for an
underlying malignancy and to perform age-appropriate Normal
cancer screening. Childhood dermatomyositis is rarely
associated with an underlying malignancy.
Pathogenesis: The exact etiology of dermatomyositis
is unknown. It has been theorized to occur secondary
to abnormalities in the humoral immune system. The
precise mechanism is under intense research. Myopathy
Histology: Histological examination of a skin biopsy
specimen shows an interface lymphocytic dermatitis.
Hydropic change is seen scattered along the basilar cell
layer. The epidermis has varying degrees of atrophy. A Electromyogram shows fibrillations
superficial and deep periadnexal lymphocytic infiltrate
is common. The presence of dermal mucin in abun- 1. Nonspecific hypergammaglobulinemia; low incidence of antinuclear antibodies
dance is another histological clue to the diagnosis. A and rheumatoid factor
muscle biopsy often shows atrophy of the involved Laboratory
muscle with a dense lymphocytic infiltrate. findings 2. Elevated serum enzymes. creatine phosphokinase (CPK), aldolase, and aspartate
Treatment: There is no known cure for dermato- amine transferase (AST, SGOT)
myositis, although some cases spontaneously remit. 3. Elevated urinary creatine and myoglobulin levels
Cases associated with an underlying malignancy have
been shown to go into full remission with cure of the
underlying cancer. Relapse of dermatomyositis in these
patients should prompt the clinician to search for a agent to keep the disease at bay. Many steroid-sparing the itching and decrease some of the redness. The
recurrence of their malignancy. Initial treatment is agents have been used, including hydroxychloroquine, treatment of juvenile dermatomyositis is similar. It is
usually with prednisone, which acts as a nonspecific quinacrine, cyclosporine, intravenous immunoglobulin believed to have a better prognosis, because few cases
immunosuppressant. The addition of a steroid-sparing (IVIG), azathioprine, and methotrexate, all with vari- are associated with an underlying cancer. It is thought
agent is almost always needed to avoid the long-term able success. Combination therapy is the norm. that early treatment of juvenile dermatomyositis
side effects of prednisone. Some patients require a The use of sun protection and sunscreen cannot decreases the risk of developing severe calcinosis cutis
smaller dose of prednisone along with a steroid-sparing be overemphasized. Topical corticosteroids help relieve during the course of the disease.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 91