Other Intracytoplasmic Organisms

■ Histoplasmosis—Histoplasma capsulatum (fungus)

■ Rhinoscleroma—Klebsiella rhinoscleromatis (gram-negative bacillus)

■ Granuloma inguinale-Calymmatobacterium granulomatis— gram-negative bacillus (Donovan body).

References:

1. Hepburn MC. Cutaneous leishmaniasis. Clin Exp Dermatol 2000; 25:363-370.

2. Grevlink SA, Lerner EA. Leishmaniasis. J M Acad Dermatol 1996; 34:257-272.

URTICARIA PIGMENTOSA, NODULAR

Diffuse dermatitis with prominent mast cells.

Synonym: Mastocytosis

Clinical Presentation:

■ Generalized eruption

■ Orange-brown macules papules and nodules on trunk less often extremities (Fig. 8A)

■ Often pruritic

■ Lesions develop wheal and flare following trauma (positive Darier's sign)

Histopathology:

■ Diffuse mast cell infiltrates throughout much of the dermis (Fig. 8B)

■ Monomorphous mononuclear cells with round to oval centrally placed nuclei and granular amphophilic cytoplasm ("fried egg") (Fig. 8C)

■ Granules are metachromatic (red) with Giemsa stain (Fig. 8D)

■ Tryptase and CD 117 positive

Pathophysiology:

■ Aberrations in C-kit pathway have been implicated References:

1. Yang F et al. Paraffin section immunophenotype of cutaneous and extracutaneous mast cell disease. comparison to other hematopoietic neoplasms. Am J Surg Pathol 2000; 24:703 -709.

2. Buttner C et al. Identification of activating C-kit mutations in adult but not in childhood onset indolent mastocytosis. J Invest Dermatol 1998; 111:1227-1231.

Figure 2 Sweet's syndrome. (A) Nodular infiltrate of neutrophils. (B) Neutrophilic fragmentation (leukocytoclasis). (C) Marked papillary dermal edema.
Figure 3 Granuloma faciale. (A) Reddish brown nodules. (B) Nodular mixed infiltrate sparing the papillary and perifollicular dermis. (C) Neutrophils, nuclear dust, eosinophilis, and plasma cells.
Figure 5 Lymphoma. (A) Deep red nodules of cutaneous lymphoma. (B) Diffuse dermal infiltrate of atypical lymphocytes. (C) Atypical lymphocytes involving follicles.
Figure 6 Erythema elevatum diutinum. (A) Reddish nodules on the fingers. (B) Diffuse neutrophilic infiltrate. (C) Neutrophils with leukocytoclasis (nuclear dust).
Figure 7 Leishmaniasis. (A) Ulcer on helix (Chiclero's ulcer). (B) Diffuse dermal infiltrate of plasma cells and histiocytes. (C) Parasitized histiocytes with numerous leishmania organisms.
Figure 8 Urticaria pigmentosa, nodular. (A) Orange-brown nodules. (B) Diffuse infiltrate of mast cells. (C) Mast cells with oval nuclei and granular cytoplasm. (D) Giemsa stain-reddish cytoplasmic granules.

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