MIS-C, inherited metabolic diseases and methylmalonic acidemia: a case report and review of the literature

Abstract

Abstract Bacground Methylmalonic acidemia (MMA) secondary to mutase deficiency, mut0, is an inborn error of metabolism causing complete enzyme deficiency. Multisystem Inflammatory Syndrome in Children (MIS-C) is a hyperinflammatory syndrome characterized by fever, inflammation, multiorgan impairment that manifests 14–60 days after the SARS-CoV-2 infection in patients aged < 21 years. Case presentation We describe the clinical case of a 2-year-old child with MMA secondary to mutase deficiency, with the documented homozygous mutation c.2179 C > T of MMUT gene, associated to mut0 phenotype. One month after SARS-CoV-2 infection, he presented fever, rash, significant increase of C-reactive protein (CRP), ferritin, triglycerides, (interleukin) IL-6, PRO-BNP, compatible with the diagnosis of MIS-C. He was treated with intravenous immunoglobulins (2gr/Kg), methylprednisolone (2 mg/Kg/day), with rapid clinical improvement. Ten days later, he showed the worsening of clinical conditions, with the recurrence of fever, vasculitic rash with palmoplantar extension, further increase of ferritin (1033 ug/l), IL-6 (146 pg/ml), PRO-BNP (5117 pg/ml), triglycerides, anemia, thrombocytopenia, metabolic acidosis with hyperlactatemia (180 mg/dl), increased urinary methylmalonic acid (200 mmol/mCreat), multiorgan failure. He was treated with sodium bicarbonate, thiamine, coenzyme Q, vitamin C, methylprednisolone and anakinra (2 mg/Kg/day). Three days after the start of anakinra, he showed a significant improvement of clinical and biochemical parameters and defervescence. 20 days later, a sepsis from Staphylococcus Aureus and Candida Albicans required the interruption of anakinra, with the worsening of the clinical and haematological parameters and the exitus. Conclusions Only a few cases of patients with inherited metabolic diseases (IMD) and MIS-C are described. However, to our knowledge, this is the first case of MIS-C in MMA described. The description of these clinical cases is a precious lesson for pediatricians to manage IMD therapeutic emergencies. Anakinra must be considered as a safe treatment of choice in IMD patients with MIS-C. The use of anakinra in patients with a severe form of MMA is safe and can be employed to treat MIS-C, gaining a substantial clinical and biochemical improvement.