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Year : 1990  |  Volume : 56  |  Issue : 2  |  Page : 152-155

A histopathological and electron microscopical observation of urticaria pigmentosa

Zhu Ke-jian, Zhu Tie-Cheng, Shi Yuan-he, Ge Zheng-Yi 

Correspondence Address:
Zhu Ke-jian


In a case of urticaria pigmentosa, histopathological and electron microscopical observation of skin lesions before and after dermatographism were compared. The results showed that the shape, membranes, nuclei and granules of mast cells in the lesions before and after dermatographism are different. The prognosis, the clinical significance of dermato­graphism test and the pattern of degranulation in urticaria pigmentosa are discussed.

How to cite this article:
Ke-jian Z, Tie-Cheng Z, Yuan-he S, Zheng-Yi G e. A histopathological and electron microscopical observation of urticaria pigmentosa.Indian J Dermatol Venereol Leprol 1990;56:152-155

How to cite this URL:
Ke-jian Z, Tie-Cheng Z, Yuan-he S, Zheng-Yi G e. A histopathological and electron microscopical observation of urticaria pigmentosa. Indian J Dermatol Venereol Leprol [serial online] 1990 [cited 2020 Jul 10 ];56:152-155
Available from: http://www.ijdvl.com/text.asp?1990/56/2/152/3512

Full Text

Urticaria pigmentosa is a rare disease. Little has been done with the histopathological and electron microscopical observation on the skin lesion before and after dermatographism test. We report a case.

 Case Report

A fifteen-year-old girl had generalized skin involvement with pigmented patches for nearly fifteen years. The lesions first appeared when she was seven months old, in the retro-auricular region and neck as pruritic blisters ranging from the size of a grain of rice to a ping-pong ball. Tawny patches were left after healing. The lesion recurred, more gravely in summer, extend­ing to the extensors of the extremities and back. At the age of eight, pruritus disappeared and its colour faded year by year. Other systems were normal, and her family was unaffected. Physical examination was normal except for the skin. The lesions were generalized. They were tawny or light brown, sharply defined macules. The colour on the lesions was un­changed under diascopy. Those located at the neck were rough. Nodules and plaques were not seen. The mucosae, palms, soles, axillae and groins were spared. A dermatographism test was performed with the instrument made by one of the authors[1] at the definite velocity of 5 cm/5s and different pressures of 50 gm, 100 gm and >100 gm. A positive response of pruritic wheals appeared on the skin lesions within 2 minutes lasting 10 minutes (positive Darier's sign), while the response was negative in the region without the lesions. Routine complete blood count, urinalysis, stool, SGPT and serum TTT, ZnTT and A/G ratio were normal. Liver­spleen scan and a bone marrow aspiration showed no abnormalities. Examination of the chromosome configuration indicated 46 XX. A biopsy specimen was taken from the skin lesion on the neck before and after dermatographism respectively, and equally divided each into two pieces. One of them was treated with routine paraffin-embedded sections and hematoxylin­eosin, Giemsa and toluidine blue staining; while the other prepared for electron micro­scopy was double-fixed with 2.5% glutaral­dehyde and 1% osmic acid phosphate buffer, embedded with epoxy resin and then ultrathin sections were made, stained with uranyl acetate and lead citrate and observed with a Philips EM 410 electron microscope. On H and E staining, the papillary dermis especially around the capillaries, had a lot of spindle-shaped cells. The cytoplasma of these cells was crowded with purplish red metachromatic granules identified with toluidine blue and Giemsa staining. Comparison of the slides before and after dermatographism revealed no significant difference in the structure and shape of mast cell. On electron microscopy, the structure and shape of mast cells was similar to those in normal skin, there were nu merous long microvilli projecting at their periphery and numerous characteristic granules in their cytoplasm. There were however, differences between the specimens of pre-dermatographism and that of post­dermatographism. These were : (1) Post­dermatographically, the mast cells became atypical, stellate or spindle in shape with incomplete cytoplasmic membrane, irregular and pyknotic nuclei and concentrated meta­chromasome. Occasionally, bilobed nuclei were seen [Figure 1][Figure 2]. (2) In the intercellular spaces and between the collagenous fibres, there were single or multiple granules or even a great many of granules discharged due to the mast cells rupture, which does not occur pre­dermatographically [Figure 3]. (3) The shape of intracellular granules was similar to those in the extracellular space. The granules were enclosed by a single perigranular membrane, and occasionally by a double membrane but some had no membrane. Granules revealed scroll-like and or lamellar configuration, often blended into the amorphous finely granular material with different electron density, which is quite the opposite to those in pre-dermato­graphism specimens which were relatively uniform [Figure 4][Figure 5][Figure 6].


Mastocytosis represents a spectrum of clinical disorders that range from localized mast cell infiltrates in the skin to a widespread pro­liferative process involving multiple organs.[2] The prognosis varies with the age at onset. In general, the prognosis is favourable in that nearly 80% will be either markedly improved or free of disease by early adulthood. How­ever, in patients who develop mastocytosis as an adult, the disease usually persists throughout life and these patients appear to be at a greater risk than children for systemic involvement.[2]

When the cutaneous lesion of mastocytosis is stroked firmly or rubbed it often becomes pruritic and develops a wheal (Darier's sign). Very young children may vesiculate in the region of the stroked cutaneous lesion. In upto 50% of the patients, stroking of macroscopically uninvolved skin also produces a wheal of der­matographia due to microscopic dermal masto­cytosis.[3] Therefore, the significance of positive dermatographism test in mastocytosis is as follows : (1) A positive dermatographism test on cutaneous lesions (Darier's sign) is patho­gnomonic sign to diagnose urticaria pigmentosa. (2) Positive Darier's sign in macroscopically uninvolved skin suggests a dermal mastocytosis with or without skin lesions or it probably exists along with extracutaneous systemic involvement. In our case. Darier's sign was positive on the skin lesion and negative on macroscopically uninvolved skin. The lowest positive pressure was 50 gn1 and 100 gm respectively. But the lowest positive pressure on clinically uninvolved skin in all types of mastocytosis with or without skin lesions remains unknown.

The electron microscopic observation of the skin lesions confirmed that degranulation occurred after dermatographism. It is also suggested that besides exocytosis of a single or multiple granules, there was another pattern of degranulation when mast cells ruptured. It has been thought to result from physical stimu­lation such as stroking. A gentle action gives rise to exocytosis while a strong action leads to rupture of the cells. The loss of electron density of mast cell granules during degranulation, possibly suggests mediator release.[4],[5] The different electron density of intracellular and extracellular granules after dermatographism indicates that mediators are released inside or outside the cells. This suggests that the mediators are released at the same time as the mast cells become degranulated. When exocytosis is not prompt enough for the discharge of mast cell granules and the release of mediators after being activated, rupture of the cells occurs. Thus, it is reasonable to avoid active factors of mast cells and to choose those drugs that can stabilize the mast cell membrane as well as to use anti­histamine drugs etc till we can find an effective cure.


1Zhu Tie-cheng : Evaluation of three skin tests in physical urticaria, Chin Med J, 1988; 101 : 377.
2Tharp M D et al : Ultrastructural morphometric analysis of lesional skin : Mast cells from patients with systemic and nonsystemic mastocytosis, J Amer Acad Dermatol, 1988; 18 :298.
3Lewis RA and Austen KF : The mastocytosis syndrome, in : Fitzpatrick TB et al : Dermatology in General Medicine, 3rd ed, McGraw-Hill, New York, 1987; p 1899.
4Freeman RG : Diffuse urticariaa pigmentosa, Amer J Clin Pathol, 1967; 48 : 187.
5James MP et al : Familial urticaria pigmentosa with giant mast cell granules, Arch Dermatol, 1981; 117 : 713.


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