A phenocopy defect: Anti-IL12p70 autoantibodies in a teenage girl With bone tuberculosis and multiple recurrent abscesses: the second case reported.

* Introduction. Phenocopies of PIDs are rare diseases caused by a somatic mutation or autoantibodies against various cytokines producing clinical manifestations similar to monogenic PIDs. Sim reported the case of a Cambodian woman diagnosed at age 45 after a 13-year history of intractable bloody diarrhea, rectal granulomata, perirectal and pelvic abscesses with fistulae, recurrent suppurative lymphadenitis caused by Burkholeria gladioli. * Presentation of the case: A fourteen-year-old girl with a 2-year history of weight loss (21 kg), multiple recurrent abscesses in limbs, lungs, and spleen, rib fracture, complicated recurrent pneumonia, pyelonephritis, osteomyelitis, and septic shock, without fever. She also developed left thoracic herpes zoster and pulmonary tuberculosis. She required many hospitalizations (1 per month) for abscesses, infections, oxygen supplementary, with a poor quality of life. Chest computed tomography: multiple bilateral bronchiectases. Laboratory workup: chronic anemia, leukocytosis, neutrophilia, mild lymphopenia, thrombocytosis, hypergammaglobulinemia, elevated acute serum reactants. Lymphocyte subsets were low but present. Mycobacterium tuberculosis was detected via polymerase chain reaction (PCR) in a bone biopsy specimen from ankle osteomyelitis. Whole-exome sequencing failed to identify a monogenic defect. IL-12 was found markedly elevated in serum from our patient. Phosphorylation of STAT4, induced by increasing doses of IL-12, was neutralized with serum from the patient, thus indirectly confirming the presence of anti-IL12 autoantibodies. She received intravenous immunoglobulin, with a good but short-lived response. After receiving rituximab and anti-mycobacterial antibiotics, the patient showed a spectacular response. She now lives a normal life after four years of follow-up.
*Discussion: Phenocopies of PIDs are rare. Here, we presented a second case of Anti-IL12p70 autoantibodies in a teenage girl. We need to think about this diagnosis in patients with late-onset weight loss, multiple recurrent abscesses, and lung and bone infections caused by intracellular microbes. Treatment with anti-CD20 monoclonal antibodies might be effective and long-term follow-up is needed.

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