Biotinidase deficiency—masquerade of primary immunodeficiency disease in neonate

Biotinidase deficiency, a rare metabolic disorder characterised by abnormal biotin metabolism, affects the biotin-dependent carboxylase functions. Primarily characterised by neurological and skin disorder, it may present with myriad features. Early recognition is important for preventing long-term morbidities. Here, we describe a case of a neonate presenting with seizures and a clinical picture suggestive of immunodeficiency. Multiple superficial abscesses along with septic arthritis of the left knee and left hip led to suspicion of primary immunodeficiency disorder. On evaluation, there was severe biotinidase deficiency. The neonate was supplemented with biotin, after which there were no further episodes of severe infection requiring hospitalisation, seizures or skin manifestation. This case report highlights the wide spectrum of clinical picture these disorders may present with and the low threshold for their evaluation and treatment.