CD40LG and hidradenitis suppurativa: For patients with lesions at atypical sites for hidradenitis suppurativa, screening for conditions with defective immune function may include complete blood count, differential, and peripheral smear immunoglobulin (Ig) A, IgM, IgG, and IgE tests, total complement levels, HIV testing, serum protein electrophoresis, urine for Bence-Jones protein [19].