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Skin-nontumor / Clinical Dermatology

Other dermatoses

Mastocytosis of skin

Reviewer: Mowafak Hamodat, MB.CH.B, MSc., FRCPC, Eastern Health, St. Johns, Canada (see Reviewers page)
Revised: 1 August 2011, last major update August 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● Either urticaria pigmentosa, solitary mastocytoma, diffuse and erythrodermic cutaneous mastocytosis or telangiectasia macularis eruptiva perstans

Clinical features

● At birth or during the first 3 months of life
● May present with flushing attacks due to high histamine content
● Spontaneous involution frequently occurs
● CD117 mutations in patients with mastocytosis
Urticaria pigmentosa: most common form of mastocytosis of skin; usually childhood onset of multiple brown macules; systemic variant is malignant and involves liver, spleen, bone marrow, lymph nodes and occasionally peripheral blood (mast cell leukemia)
Darierís sign: stroking skin releases histamine, causing hives
Dermatographism: dermal edema resembling hives due to stroking with pointed instrument

Clinical description

● Solitary lesion, or small group as part of urticaria pigmentosa
● Affect extremities and trunk, not palms and soles
● May blister
● Red, brown pink or yellow nodules, or plaques measuring up to 1.0 cm

Clinical images

Urticaria pigmentosa


Micro description

● Within the macules and plaque, mast cells are predominantly in papillary dermis
● Mast cells are round or spindle shaped with abundant eosinophilic cytoplasm, distinct cytoplasmic boundaries, large pale nuclei
● Eosinophils are often present
● Also edema of papillary dermis, subepidermal vesiculation
● Bullous mastocytosis may be diagnosed by Tzank smear; infiltrate may be slight and perivascular
● In telangiectasia macularis eruptive perstans, features may be subtle, with increased mast cells around dilated superficial capillaries, basal cell hyperpigmentation of overlying epidermis, superficial lymphohistiocytic infiltrate

Positive stains

● Giemsa, toluidine blue (highlights metachromatic granules), tryptase, chloracetate esterase (Leder stain), CD117, CD2, CD25

Differential diagnosis

● Chronic dermatitis, nodular prurigo, and venous stasis: typically associated with granulation tissue and foci of neovascularization

End of Skin-nontumor / Clinical Dermatology > Other dermatoses > Mastocytosis of skin

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