A patient with WHIM syndrome presenting relatively low TREC, KREC, and housekeeping gene levels by newborn screening -a case report and the literature review ^-

WHIM syndrome is the inborn errors of immunity characterized by warts, hypogammaglobulinemia, infections, and myelokathexis, by the pathogenic variant in <i>CXCR4</i>. Patients with WHIM syndrome demonstrate neutropenia and lymphopenia due to the impaired migration of neutrophils and lymphocytes from the bone marrow. Diagnosis of patients with WHIM syndrome is often challenging, because some patients with WHIM syndrome do not show all characteristic four manifestations. T-cell receptor excision circle (TREC) and kappa-deleting recombination excision circle (KREC) assay is used for the screening of disease, such as severe combined immunodeficiencies and X-linked agammaglobulinemia. Several reports have shown that patients with WHIM syndrome show relatively low TREC or KREC levels, sometimes below the cut-off value. We present a patient with WHIM syndrome who developed recurrent viral and bacterial infections with myelokathexis. We assessed TREC, KREC, and a housekeeping gene marker levels at 5 days after birth and 3 years of age; although all values were relatively low, they remained above the established cut-off thresholds. We reviewed reports on TREC, KREC, and housekeeping gene levels in patients with WHIM syndrome and found that these patients generally showed relatively low levels of all three markers, with some values falling below the established cut-off thresholds.