Idiopathic CD4+ Lymphocytopenia Due to Homozygous Loss of the CD4 Start Codon

Idiopathic CD4+ lymphocytopenia (ICL) is an extremely rare condition characterized by low numbers of CD4+ cells (<0.3 K/μL) without human immunodeficiency virus (HIV) infection or any other cause of immunodeficiency. In this case report, we report a case of idiopathic CD4+ lymphocytopenia in a 22-year-old woman initially presenting with insomnia, fatigue, and a sore throat. However, this rapidly progressed to shortness of breath and chest pain, ultimately leading to acute respiratory distress syndrome (ARDS) over the span of a few days. Broad-spectrum antimicrobials were administered, resulting in prompt recovery. Serological studies were negative for malignancy and severe infections, including HIV1 and HIV2. Flow cytometry revealed an absence of CD4+ cells and an increase in double-negative T-cells. Further genetic workup revealed that in the second exon of the CD4 gene, the patient had a homozygous c.1ATG>GTG (p.Met1Val; p.M1V) mutation. Family screening showed that the patient's mother, father, and brother all had a single p.M1V mutation, allowing for deleterious effects to be partially offset by the normal copy of the gene. We have provided an organized analysis of the existing literature in addition to a concise overview of this case, with the intention of identifying patterns in presentation, clinical course, and outcomes. This case discusses the effects of the loss of the CD4+ start codon in the patient. Although this specific form of lymphocytopenia is very uncommon, it illustrates the importance of genetic testing and the integral nature of laboratory testing in therapy charting.