We report the first case of long-lasting ARDS secondary to IRIS and combined CMV and PJ pulmonary opportunistic infections after treatment in a patient with TCN2 deficiency, in contrast to previously reported cases of children with TCN2 deficiency who exhibited excellent clinical outcomes following treatment with vitamin B12 [11,13,14,15,16,17,18]. The gene discussed is TCN2; the disease is hyperinsulinemic hypoglycemia, familial, 4.