From the Guidelines
Cap grass syndrome, also known as allergic rhinitis caused by grass pollen, can be effectively managed with allergen immunotherapy (AIT) for a duration of at least 3 years to achieve long-term clinical and immunological tolerance. The optimal duration of AIT is not well defined, but recent studies suggest that 3 years of treatment can induce clinical and immunological allergen-specific tolerance, defined as the persistence of clinical benefit for at least 1 year after cessation of treatment, accompanied by altered antigen-specific T-cell and/or B-cell responses 1.
Key Findings
- A 7-year trial by Durham et al, as mentioned in the study by Gurgel et al 1, demonstrated that 3 to 4 years of grass pollen AIT resulted in persistent efficacy for at least 3 years after the discontinuation of AIT.
- A larger 5-year double-blind, placebo-controlled, randomized trial consisting of a 3-year treatment phase followed by 2 years of blinded follow-up in adults with a history of moderate-to-severe grass pollen ARC resulted in a reduction in mean symptom scores of 25% to 36% and reduction in medication scores by 20% to 45% in the AIT group over the 5 consecutive grass pollen seasons 1.
- Scadding et al demonstrated that 2 years of either SCIT or SLIT were insufficient to maintain tolerance to grass pollen NAC at 1 year after treatment discontinuation, highlighting the importance of at least 3 years of AIT 1.
Management Approach
- Allergen immunotherapy (AIT) should be continued for a period of at least 3 years to achieve disease modification and long-term clinical and immunological tolerance.
- The decision to continue or stop immunotherapy must be individualized, considering factors such as the severity of disease, benefits sustained from treatment, and convenience of treatment.
- A clinical improvement can be reasonably expected in the first year of AIT, and the patient’s response to AIT should be evaluated on a regular basis to determine the effectiveness of treatment and potential causes of lack of response 1.
From the Research
Cap Grass Syndrome
- There is no direct evidence of "Cap grass syndrome" in the provided studies, however, two separate conditions can be identified: Capgras syndrome and grass pollen-induced allergic rhinitis.
- Capgras syndrome is a delusional belief that a person or persons have been replaced by doubles or impostors, as described in studies 2 and 3.
- Grass pollen-induced allergic rhinitis is a common disease affecting millions of people worldwide, with treatment options including symptom-alleviating drugs and immunotherapy, as discussed in studies 4, 5, and 6.
Treatment Options for Allergic Rhinitis
- Intranasal corticosteroids, such as fluticasone propionate, are considered the most effective medication class for controlling allergic rhinitis 4 and 6.
- Oral antihistamines, such as cetirizine, are also effective in treating allergic rhinitis, although they may not be as effective as intranasal corticosteroids in some cases 4 and 6.
- Immunotherapy, including subcutaneous and sublingual treatment, is a potentially curative option for grass pollen-induced allergic rhinitis, with sublingual tablet treatment considered safer than subcutaneous treatment 5.
Capgras Syndrome Characteristics
- Capgras syndrome is characterized by a delusional belief that a person or persons have been replaced by doubles or impostors 2 and 3.
- The syndrome can occur in the context of both psychiatric and organic illness, and is related to lesions of the bifrontal and right limbic and temporal regions 2.
- Neuroimaging studies have revealed brain lesions in patients suffering from Capgras syndrome, and have suggested a common neuroanatomic basis for Capgras syndrome and obsessive-compulsive disorder 2.