Page 147 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-62 Rashes

PSEUDOXANTHOMA ELASTICUM

Pseudoxanthoma elasticum is a rare genetic disorder
with both cutaneous and systemic findings. It is inher-
ited in an autosomal recessive manner. This disease is
caused by a defect in an adenosine triphosphate (ATP)-
binding protein that is found in many tissues, including
the skin, eye, gastrointestinal tract, and cardiovascular
systems. The cutaneous findings often precede the
appearance of the systemic findings. Recognition of the
cutaneous findings can help lessen the risk of systemic
complications. A multidisciplinary approach to the care
of these patients is required. The skin findings have no
bearing on mortality.
Clinical Findings: Pseudoxanthoma elasticum mani-
fests in late childhood or early adulthood. The cutane- Angioid streaks. Rupture of Bruch’s
ous findings are almost always the first sign of the membrane, likely due to abnormal
disease. The skin on the neck is most commonly calcification of the membrane, can
affected early and most severely. There is a “plucked be seen in pseudoxanthoma
chicken” appearance to the skin. Small yellow papules elasticum on slit-lamp examination.
are studded within the involved region, and over time
they coalesce into larger, symmetric plaques. The inter-
vening skin has a dull appearance with a fine pebbly
texture. The neck is by far the area most noticeably
affected, but other regions may become involved,
including the intertriginous regions. A rare generalized
cutaneous form has been reported. The mucous mem-
branes may also become involved with tiny yellow
papules. As time progresses, the skin may become loose,
appearing to hang from the body, and this can be a
significant cosmetic concern to the patient. The areas
of cutaneous involvement are essentially asymptomatic. The neck is often the first area of skin involvement. Often clinically
On occasion, mild pruritus is reported. A nonspecific noted to have the appearance of “plucked chicken skin”
skin finding that is seen with increased frequency in
pseudoxanthoma elasticum is elastosis perforans ser-
piginosa. This perforating disorder has been described
to occur in many different clinical settings, and it is
caused by the transepidermal elimination of damaged
elastic tissue. The reason this occurs in pseudoxan-
thoma elasticum is unknown.
It is important to diagnosis this disease at a young
age so that some of the severe systemic complications
can be prevented. The globe is affected in pseudoxan-
thoma elasticum. The first sign is a yellowish discolor-
ation of the retina. Later in life, cracks or ruptures in
Bruch’s membrane can be seen on funduscopic exami-
nation; these are termed angioid streaks. Angioid streaks
have a later age at onset than the cutaneous findings do.
Abnormalities of the elastic fibers in Bruch’s membrane
are responsible for their formation. Angioid streaks can
be seen in many disorders of connective tissue and are
not specific for pseudoxanthoma elasticum. Retinal
hemorrhage and resultant visual field loss is the most Low power (H&E). Fragmented and calcified High power (H&E). Basophilic clumping of calci-
severe ophthalmological complication. elastic fibers appear as basophilic clumps within fied elastic fibers that have become fragmented
Cardiovascular and gastrointestinal manifestations the middle to lower dermis. This is highly is well appreciated in this highpower view. The
arise because of the abnormal calcification of elastic characteristic for pseudoxanthoma elasticum. abnormality in the elastic fibers leads to the
tissue within blood vessel walls. Gastrointestinal hem- various clinical manifestations of the disease.
orrhage may occur and may be life-threatening. Angina
and hypertension may occur from involvement of the
coronary and renal arteries, respectively.
Histology: Findings on skin biopsies are very charac-
teristic and show abnormal fractured, calcified elastic (MRP6), which is also known as ATP-binding cassette examinations can help keep hypertension and early
tissue within the dermis. The findings can be accentu- transporter 6 (ABCC6). This protein is found within signs of retinal disease in check. Retinal hemorrhages
ated with special staining methods to highlight the cal- the liver and kidneys and is expressed at low levels in need to be treated acutely by an ophthalmologist. Routine
cified elastic fibers. However, the diagnosis can be made the tissues that are affected by this disease. It has been examinations for blood in the stool and routine gastroin-
easily on routine hematoxylin and eosin staining. proposed that the defect causes a metabolic abnormal- testinal examinations are warranted to screen for gastro-
Pathogenesis: Pseudoxanthoma elasticum is inherited ity, possibly resulting in a buildup of a metabolite that intestinal bleeding, which is the main cause of morbidity
in an autosomal recessive fashion and is caused by a damages to the elastic fibers in the affected tissue. and mortality in these patients. Patients should be
defect in the ABCC6 gene. This gene is responsible for Treatment: Therapy is directed at preventive encouraged to stay within a healthy weight range and not
encoding the multidrug resistance–associated protein 6 care. Routine cardiovascular and ophthalmological to smoke. Most patients live a normal life span.

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