During acute disease stages, perifollicular CD4+ and intrafollicular CD8+ T lymphocytes form extensive infiltrates around anagen HFs, described histologically as a ‘swarm of bees’, disrupting matrix cell proliferation and inducing HF keratinocyte apoptosis, ultimately inhibiting cell division within the hair matrix and producing dystrophic hair shafts [13,83]. This evidence concerns the gene CD4 and Hand-foot syndrome.