Hyperserotonemia in Egyptian autistic children: Relation to allergic manifestations

One of the most consistent biological findings in autism is elevated blood serotonin levels. Immune abnormalities, including allergy, are also commonly observed in this disorder. Allergy may play a role in pathogenesis of autism wherein immune responses to allergens may induce the production of brain autoantibodies found in many autistic children. Hyperserotonemia may be the reason behind the increased frequency of allergic manifestations in autistic children through reduction of T-helper 1-type cytokines. Thus, we investigated the possible connection between hyperserotonemia and the increased frequency of allergic manifestations in 40 autistic and 40 healthy matched children. Autistic children had significantly higher serum serotonin levels than controls [125 (250.75) vs. 41.5 (41.5) ng/mL, P < 0.001]. Fifty five percent (22/40) of autistic children had elevated serum serotonin. Allergic manifestations (bronchial asthma, atopic dermatitis and allergic rhinitis) were elicited in 45% of autistic patients which were significantly higher than controls (10%, P < 0.001). Moreover, autistic patients with allergic manifestations had significantly higher serum serotonin levels than those without (P < 0.001). Furthermore, there was a significant positive correlation between serum serotonin and total immunoglobulin E levels in autistic patients (r = 0.8, P < 0.001). In conclusion, hyperserotonemia may be a contributing factor to the increased frequency of allergic manifestations in some autistic children. Inclusion of serum serotonin levels as a correlate may be useful in future immune studies in autism to help unravel the longstanding mystery of hyperserotonemia and its possible role in the pathophysiology of this disorder. In addition, the effect of blood serotonin lowering drugs in hyperserotonemic autistic children, on amelioration of allergic manifestations and immune abnormalities, should be studied.