PIGMENTED PURPURA
The pigmented purpuras
are a group of idiopathic rashes that can occur at any age. They are grouped
together because of their similar clinical and histological presentations. They
are believed to be caused not by vasculitis but by inflammation of the small
cutaneous capillaries, which produces a capillaritis. The rash is typically of
no clinical significance to the patient, but it can cause significant cosmetic
concern, and the purpuras need to be differentiated from other conditions that
can cause similar rashes. The five rashes that make up the pigmented purpuric
family of rashes are Schamberg’s disease, eczematous pigmented purpura of
Doucas and Kapetanakis, pigmented purpura of Gougerot and Blum, lichen aureus,
and Majocchi’s disease (annular telangiectatic pigmented purpura).
Clinical Findings: These entities are grouped together for many reasons. They are believed
by some to be slightly different manifestations of the same disease state, and
the histopathology of all the variants is strikingly similar. The pigmented
purpuric dermatoses are benign and are not associated with any underlying
abnormality. They can occur at any age. They are almost entirely asymptomatic
in nature. The true incidence of these conditions is unknown, because they are
often not reported. They are believed to occur very commonly.
Schamberg’s disease is the most frequently encountered
of the pigmented purpuric eruptions. It almost universally begins on the lower
extremities. It manifests as tiny (1-mm) cayenne pepper–like petechial macules
of the skin. Over time, a brownish-red hyperpigmented background forms
secondary to the extravasation of red blood cells and their subsequent
breakdown within the skin to release hemosiderin. The lesions are nonblanching
and nonpalpable. The rash may spread proximally up the lower extremity but
rarely affects other areas of the body. Most patients are referred to the
dermatologist to rule out vasculitis, which is easily done by not finding any
evidence of palpable purpura. The rash is almost always entirely asymptomatic,
and patients frequently complain only of the appearance. If one sees widespread
petechia, a platelet count should be performed to look for thrombocytopenia. If
the platelet count is normal, a skin biopsy of the upper extremity or truncal
area of involvement should be performed to evaluate for the very rare form of
pigmented purpuric mycosis fungoides.
Eczematoid pigmented purpura of Doucas and Kapetanakis
is a rare variant that manifests with petechiae and hyperpigmentation but is
also associated with an overlying eczematous eruption. This form is typically
pruritic and can show secondary excoriations.
Pigmented purpura of Gougerot and Blum is also known
as lichenoid pigmented purpura. Small, light pink to purple papules form on the
lower extremities. They can be mistaken initially for lichen planus. Biopsies
of these papules show a lichenoid infiltrate. This pigmented purpura can be
distinguished from Schamberg’s disease in that the skin findings are palpable.
There is no true palpable purpura.
Lichen aureus can be seen at any age and manifests
with the presence of multiple tiny, golden-colored macules that coalesce into a
large macule or patch. Lichen aureus can occur anywhere on the body and is
solitary in nature.
The involved regions in Majocchi’s disease show
annular patches with petechiae and hyperpigmentation from hemosiderin deposition. This is a rare form of
pigmented purpura that typically starts on the legs and spreads slowly over
time.
Pathogenesis: The pigmented
purpuric dermatoses are believed to be caused by capillaritis. The exact
etiology is unknown.
Histology: The
histological findings are similar across all variants. Extravasation of red
blood cells is prominent. The extravasation is seen in the vicinity of the capillaritis. The infiltrate is predominantly
lymphocytic. The presence of hemosiderin is more easily seen in chronic
lesions.
Treatment: There is no
agreed-upon standard therapy, and withholding therapy is a frequently used
option. Anecdotally, topical corticosteroids may be tried for a few weeks. Oral
vitamin C and bioflavonoids have been reported to be successful, again mostly
in anecdotal reports.
