Mastocytosis in man is characterized by an increased number of mast cells in different organs, and its cause is still unknown.6 In domestic animals, mastocytosis is characterized by cutaneous tumors in ferrets, dogs and cats, cattle and horses.9-11 Systemic mastocytosis is rare in dogs and cats, goats, and pigs.3,8,12 There is only one report of mastocytosis in zoo or wild animals (i.e., a gerbil with dermal and systemic mastocytosis).5 Apart from that, no evidence of reports in nonhuman primates was found. Herewith, the first report of mastocytosis in a chimpanzee, housed in the Royal Zoological Society of Antwerp, is presented.
Chimpanzee “Maaike” (wild-born in early 1985) was brought to the zoo in July 1985. She was quarantined and underwent routine treatment. Afterward, she developed as a normal animal in the group.
In 1995, Maaike gradually began scratching herself more than the other animals of her group. Parasitologic and microbiologic analyses of skin samples were all negative. To control the pruritus, she was given 0.2 mg/kg astemizole, an H1-antihistamine (Hismanal, Janssen-Cilag, Berchem, Belgium) orally. The symptoms diminished but never disappeared completely, and they started again when discontinuing this treatment.
In 1996, Maaike showed skin lesions due to scratching and loss of hair. From then onward, she received three capsules of 500 mg essential fatty acids daily (Canistar Omega 3, Merial, Brussels, Belgium). For lack of improvement, she was anesthetized for blood sampling, skin biopsies and swabs. Laboratory analysis did not reveal any hematologic or biochemical anomaly. Microbiologic and parasitologic analyses were negative. Total IgE was not elevated (in comparison with human standards). IgE for different allergens was also negative (i.e., Dermatophagoides pteronyssinus, bananas, timotheegrass, Aspergillus fumigatus). Histopathology of the skin lesions at this time revealed signs of folliculitis and parakeratosis. Treatment with H1-antihistamine was continued with either cetirizine (Zyrtec, UCB Pharma, Brussels, Belgium) or loratadine (Claritine, Schering-Plough, Brussels, Belgium).
In 1997, pruritus intensified and Maaike was treated with 0.7 mg/kg methylprednisolone (Medrol, Pharmacia, Brussels, Belgium) and antibiotics to prevent secondary bacterial infections. The scratching diminished, and lesions healed almost completely; however, when this treatment was discontinued, her condition worsened again. Maaike was again anesthetized and skin biopsies taken. This time, histopathology showed signs of mastocytosis with 25–30 mast cells per field at high magnification between dermal papillae and in capillaries of the papillary layer of the dermis. Continuous treatment with a combination of the H1-antihistamine astemizole or hydroxyzine (Atarax, UCB Pharma, Brussels, Belgium) and the H2-antihistamine ranitidine (Zantac, Glaxo Wellcome, Brussels, Belgium) was restarted. Her diet was changed, and ingredients containing histamine (or liberators) or other amines were banned. She had to be fed separately and was not allowed spinach, green beans, tomatoes, sauerkraut, pineapples, bananas, lemon, grapefruit, oranges, dates, figs, strawberries, raspberries, mandarins, honey. Simultaneously, continuous treatment with 0.3 mg/kg methylprednisolone every other day and four capsules of 311.5 mg essential fatty acids (Viacutan, Boehringer Ingelheim, Brussels, Belgium) daily decreased the symptoms gradually. Until today, Maaike’s pruritus is under control, and her skin is normal again.
Discussion and Conclusion
The prevalence of human mastocytosis remains unknown, and the disease is a diagnostic challenge that can take 10 years between the onset of symptoms and the correct diagnosis.1 Blood and urine analyses for histamine and its metabolites are only useful in patients with systemic disease.6 Demonstration of mast cells in skin biopsies is most reliable.6 Because mast cells are the key effector cells in the pathogenesis of allergic diseases,7 differential diagnoses are atopy4 or exanthema,2 but immunologic tests were negative. Treatment of mastocytosis in man includes a combination of H1 and H2 histamine antagonists and possibly the intralesional injection or systemic use of glucocorticoids.1,6 Maaike was therefore treated orally with these combined histamine antagonists and methylprednisolone. Also, histamine-rich foods and mast cell degranulation triggers were avoided.6 Although Maaike is not cured definitely, her condition is under control, and she can lead a normal life in the chimpanzee group.
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