Inborn Error of Immunity or Atopic Dermatitis: When to be Concerned and How to Investigate.

Around 20% of all children worldwide suffer from atopic dermatitis. Therefore, eczematous skin lesions and elevated serum immunoglobulin E (IgE) levels are common findings. Inborn errors of immunity (IEI) may be missed in the context of atopic dermatitis, and management and prognosis of these conditions can be substantially different. Children suffering from IEIs such as hyper-IgE syndromes, Wiskott-Aldrich syndrome, immunodysregulation polyendocrinopathy enteropathy X-linked syndrome, Omenn syndrome, the atypical complete DiGeorge syndrome, and skin barrier disorders like Comèl-Netherton syndrome and severe dermatitis-multiple allergies and metabolic wasting syndrome may present with additional red flags, which should raise a clinical suspicion for an underlying IEI. These red flags may include eczematous skin lesion manifesting prior to two months of life, disseminated or recurrent viral, bacterial, or fungal infections, mucocutaneous candidiasis, purpura, chronic diarrhea, or abnormalities in development or of connective tissue. A differential blood count, as well as a lymphocyte subset analysis, total immunoglobulin levels, and vaccination titers can help the clinician to decide whether a patient with eczematous skin lesions and elevated serum IgE should be referred to a clinical immunologist for a full immunological work-up and broad genetic analysis.