{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,23]],"date-time":"2025-12-23T10:59:06Z","timestamp":1766487546893,"version":"3.48.0"},"reference-count":10,"publisher":"BMJ","issue":"12","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2025,12,5]]},"published-print":{"date-parts":[[2025,12]]},"abstract":"<jats:p>Primary immunodeficiencies are genetic disorders that impair immune function, increasing the risk of infections, autoimmune diseases and cancer. Patients with severe viral infections are often not thoroughly evaluated for immunodeficiencies. This case presents a young infant with human parvovirus B-19 meningitis and persistent lymphocytopenia, whose immunophenotyping revealed low absolute counts of T, B and natural killer cells, leading to a diagnosis of underlying immunodeficiency. This case underscores the necessity for vigilant diagnosis when standard presentation is complicated by recurrent illness or risk factors, highlighting the \u2018Think Zebra\u2019 analogy in paediatric practice.<\/jats:p>","DOI":"10.1136\/bcr-2025-270684","type":"journal-article","created":{"date-parts":[[2025,12,23]],"date-time":"2025-12-23T10:55:19Z","timestamp":1766487319000},"page":"e270684","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Human parvovirus B-19 meningitis: a sentinel event unmasking primary immunodeficiency in an infant"],"prefix":"10.1136","volume":"18","author":[{"given":"Dania Abbas","family":"Butt","sequence":"first","affiliation":[{"name":"Department of Paediatric Intensive Care Unit, National Institute of Child Health, Karachi, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1316-7104","authenticated-orcid":false,"given":"Syed Muhammad Aqeel","family":"Abidi","sequence":"additional","affiliation":[{"name":"PGME, The Aga Khan University Medical College Pakistan, Karachi, Sindh, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0067-2216","authenticated-orcid":false,"given":"Syeda Namayah Fatima","family":"Hussain","sequence":"additional","affiliation":[{"name":"Liaquat National Hospital and Medical College, Karachi, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hira","family":"Nawaz","sequence":"additional","affiliation":[{"name":"Department of Paediatric Intensive Care Unit, National Institute of Child Health, Karachi, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6580-5542","authenticated-orcid":false,"given":"Murtaza Ali","family":"Gova","sequence":"additional","affiliation":[{"name":"Department of Paediatric Intensive Care Unit, National Institute of Child Health, 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