elevated serum levels of eosinophil-derived neurotoxin and major basic protein), and increased expression of a marker for T cell activation, interleukin-2 receptor alpha chain, are absent in individuals with familial eosinophilia but common in other types of hypereosinophilia. Accompanying diseases
In spite of being generally considered a benign expression of eosinophilia, isolated cases of family members with familial eosinophilia have been afflicted with tissue dysfunctions that are often associated with more pathological forms of eosinophilia. These dysfunctions include fatal endomyocardial fibrosis, valvular heart disease, and diminished motor and/or sensory function in skin areas served by peripheral nerves. Three patients with heart tissue for pathology examination had eosinophilic infiltration or fibrosis in their hearts endomyocardium. One patient who died suddenly had autopsy findings of eosinophilic infiltration not only in the heart but also in lungs, gastrointestinal tract, and meninges. It is unclear whether these tissue damages were due to primary eosinophil infiltrations or eosinophil infiltrations secondary to other causes. Genetics
Familial eosinophilia is an autosomal dominant disorder. Genetic linkage gene mapping family studies localize the gene responsible for this disease to chromosome 5 at position q31-q33, between markers D5S642 and D5S816. Studies on other disorders associated with high levels of blood eosinophils (e.g. childhood asthma, schistosomiasis) have likewise linked eosinophilia to the q31-q33 area of chromosome 5. The 5q31-q33 region contains a cytokine gene cluster that includes genes for Interleukin 3, interleukin 5, and granulocyte-macrophage colony-stimulating factor. Each of these genes functions to promote the proliferation and differentiation of eosinophil precursor cells.
Desloratadine (trade names Clarinex and Aerius) is a tricyclic H1 inverse agonist that is used to treat allergies. It is an active metabolite of loratadine. It was patented in 1984 and came into medical use in 2001. Medical uses
Desloratadine is used to treat allergic rhinitis,  nasal congestion and chronic idiopathic urticaria (hives). It is the major metabolite of loratadine and the two drugs are similar in safety and effectiveness. Desloratadine is available in many dosage forms and under many trade names worldwide.An emerging indication for desloratadine is in the treatment of acne, as an inexpensive adjuvant to isotretinoin and possibly as maintenance therapy or monotherapy. Side effects
The most common side-effects are fatigue (1.2%), dry mouth (3%), and headache (0.6%). Interactions
Co-administration with erythromycin, ketoconazole, azithromycin, fluoxetine or cimetidine resulted in elevated blood plasma concentrations of desloratadine and its metabolite 3-hydroxydesloratadine in studies. However, no clinically relevant changes were observed. Pharmacology
Pharmacodynamics
Desloratadine is a selective H1-antihistamine which functions as an inverse agonist at the histamine H1 receptor.At very high doses, is also an antagonist at various subtypes of the muscarinic acetylcholine receptors. This effect is not relevant for the drugs action at therapeutic doses. Pharmacokinetics
Desloratadine is well absorbed from the gut and reaches highest blood plasma concentrations after about three hours. In the bloodstream, 83 to 87% of the substance are bound to plasma proteins.Desloratadine is metabolized to 3-hydroxydesloratadine in a three-step sequence in normal metabolizers. First, n-glucuronidation of desloratadine by UGT2B10; then, 3-hydroxylation of desloratadine N-glucuronide by CYP2C8; and finally, a non-enzymatic deconjugation of 3-hydroxydesloratadine N-glucuronide.