Page 131 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-46 Rashes

MAST CELL DISEASE

Solitary mastocytoma with Darier’s sign. Solitary mastocytomas
almost always self-resolve. Darier’s sign is elicited by rubbing
the mastocytoma, causing urtication.

WHO Classification for Mast Cell Disease

Cutaneous disease only (includes cutaneous
mastocytoma, urticaria pigmentosa, and
telangiectasia macularis eruptiva perstans)
Indolent systemic disease
Systemic mastocytosis with associated clonal
MAST CELL DISEASE non–mast cell hematological disease
Aggressive systemic disease
Mast cell leukemia
Mast cell disease is an uncommon condition that has Mast cell sarcoma
many clinical variants and subtypes. It can be seen as a Noncutaneous mastocytoma
solitary finding, as in the solitary mastocytoma, or it can
result in widespread cutaneous disease, as in urticaria
pigmentosa. Most mast cell disease is caused by an
abnormality in the c-kit gene (KIT) . There are many
other forms of mast cell disease, most in the benign
category; some affect the skin predominantly, and
others are more systemic in nature. One systemic type
is the rare mast cell leukemia. Other systemic forms
have been reported, such as mast cell sarcoma, and carry
a poor prognosis. It is important to recall that mast cells
are derived from the bone marrow and share certain
things in common with other hematopoietic cells. The
World Health Organization (WHO) has developed a
simplified classification system for mast cell disease (see
box to right).
Clinical Findings: Solitary mastocytoma is one of the
most common of all the mast cell disease types. It mani-
fests in early childhood, often in the first few years of
life. It appears as a yellowish to brownish macule,
papule, or plaque. On rare occasions, a lesion develops
a vesicle or bulla. Most lesions are asymptomatic until
rubbed or scratched. When this takes place, a localized
urticarial reaction occurs above the mastocytoma and Urticaria pigmentosa. This is the
extends into the surrounding skin. This sign, called most common form of cutaneous
Darier’s sign, can be used in any of the cutaneous mast mastocytosis. It can manifest with
cell diseases to help make the diagnosis. These solitary reddish-brown macules and papules
mast cell collections almost always spontaneously and in severe cases with vesicles
resolve with no sequelae. and bullae.
Urticaria pigmentosa is a more diffuse affliction of
the skin with mast cells; it has been reported to be the
most common variant of mast cell disease. From a few
to hundreds of slightly hyperpigmented macules and
plaques occur across the surface of the skin. Some
develop into vesicles and bullae. This most commonly
occurs in early childhood but has also been reported
to occur in adulthood. Most children are diagnosed on
the basis of the clinical presentation and demonstration
of a positive Darier’s sign. The condition typically runs
a benign course in children, and most cases spontane-
ously remit over a few years and then disappear at
about the time of puberty. Adult-onset urticaria pig-
mentosa is a more chronic disease that rarely remits.
Special care should be taken to continually screen adult
patients for the development of systemic mast cell or may not be present. The most common symptom is are indicative of systemic involvement, and further sys-
involvement. pruritus. The appearance can be bothersome for some. temic workup is warranted. Urine histamine and hista-
Telangiectasia macularis eruptiva perstans is a less It is most often limited to the skin, but the clinician mine metabolites can also be assessed but seem to be
commonly seen variant of mast cell disease. It occurs should evaluate for systemic involvement. less sensitive and less specific than the serum tryptase
almost exclusively in the adult population. Patients Measurement of the serum tryptase level is the most level. If systemic involvement is considered, further
often present with widespread telangiectases in unusual accurate means of screening for systemic involvement testing with a bone marrow biopsy may be indicated.
locations such as the back, chest, and abdomen. There with mastocytosis. Levels in the normal range indicate Molecular genetic testing can be performed on the bone
can be a background erythema, and Darier’s sign may cutaneous disease only; levels greater than 20 ng/mL marrow sample to assess for the KIT gene mutation.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 117