• INCLUSION CRITERIA:

To be eligible to participate in this study, an individual must meet all of the following criteria:

1. Stated willingness to comply with all study procedures and availability for the duration of the study

2. Male or female, aged 1-100

3. Ability of subject (or Legally Authorized Representative (LAR)) to understand and sign a written informed consent document

   Eosinophilic Patients only:

4. Documented peripheral blood count >1500/mm3, tissue eosinophilia (abnormal accumulation of eosinophils in the skin or other body tissues) or suspected eosinophilic end organ involvement

5. Primary (non-NIH) physician for routine medical care

   Relatives only:

6. Extended family member of an eosinophilic participant on this protocol

EXCLUSION CRITERIA:

An individual who meets any of the following criteria will be excluded from participation in this study:

1. Any condition(s) or diagnosis, physical and/or psychological, that the investigator feels precludes the patient from participation in the study.

   Relatives only:

2. Females must not be pregnant