During the winter of 2019 a novel highly pathogenic coronavirus strain called SARS-CoV2 emerged in Wuhan, China, and rapidly spread all over the world, causing more than a million deaths so far (WHO Coronavirus Disease (COVID-19) Dashboard, 2020). The consequences of the SARS-CoV2 pandemic is not limited to the people infected by the virus. Fear of SaRS-CoV2 infection motivated by hospital clusters made both urgent and chronic patients avoid seeking medical attention (1) (2). Also, mobility restrictions and the collapse of the healthcare systems made live consultations and blood analysis extremely difficult.
People with preexisting medical conditions seem to be at higher risk for severe forms of COVID-19 (3). Among them, patients with inborn errors of metabolism (IEM) pose specific management challenges, considering the multisystem involvement of many of them. This is especially true for patients with pulmonary impairment or alterations of the immune system (splenectomy, primary immunodeficiencies or neutropenia) (4) (5) (6). Even if they are not at risk or do not develop severe forms of COVID-19, any infection can trigger a metabolic decompensation that has its own important morbi-mortality and that needs to be promptly recognized and treated.
Phenylketonuria (PKU) is the most common inborn error of amino acid metabolism. Other diseases frequently followed in metabolic centers include organic acidemias (OA), maple syrup urine disease (MSUD), glutaric aciduria (GA), tyrosinemia or homocystinuria, among others. Inborn errors of amino acid metabolism are genetic conditions with varying clinical presentations, but they share common general features. Many present clinically as a life-threatening episode consisting in severe metabolic acidosis, hyperammonemia, hypoglycemia or hepatic alterations; others might present with acute or chronic neurological involvement and some might have nonspecific clinical manifestations such as failure to thrive or recurrent vomiting, among others. Nowadays, most can be diagnosed by the neonatal screening. Treatment of these disorders is based in most cases in dietary management that includes a protein restrictive diet combined with a special amino acid mixture (SAAM) that contains all amino acids except those prior to the metabolic block. Supplementation might be necessary to avoid the deficiency of the amino acid that has become essential due to the enzymatic defect (7). Treatment might also include specific cofactors such as carnitine, glycine or different vitamins (8) (9) (10) (11). Dietary treatment avoids the accumulation of toxic metabolites and is generally effective in greatly improving the outcome (12), but even well controlled patients tend to develop different physical or neurological long-term complications. All inborn errors of amino acid metabolism share the need for frequent clinical and biochemical monitoring by a multidisciplinary trained team in order to adjust treatment. However, further acute metabolic crisis can be triggered by situations that induce protein catabolism such as intercurrent infections, immunization, surgery, prolonged fasting or certain medications such as the use of high doses of glucocorticoids (13). Depending on the disease, new crisis can be life-threatening, but in all patients frequent bad metabolic controls lead to increased long-term complications. Patients and their families should be trained to early recognize risk situations and implement treatment changes to avoid metabolic decompensations.
The metabolic unit of the Hospital Ramon y Cajal in Madrid, Spain, is a national reference center for both children and adults with inborn errors of metabolism. It is currently involved in the active follow-up of more than 700 patients with all kind metabolic diseases including amino acid, fatty acid or carbohydrate metabolism, lysosomal storage diseases or mitochondrial cytopathies. The hospital is a 3rd level university facility for both children and adults with over 1500 beds and all recognized medical and surgical specialties. It houses not only ours but several other national reference centers for different pathologies.
Spain was one of the earliest and most affected countries during the first wave of COVID-19 that spread all over the world in the first half of 2020 (14). During this period, Madrid, in particular, had the highest rate of infections and hospitalizations in our country. The activity of our hospital during the months of March to May was completely shifted to attending COVID-19 patients. All but one of the physicians of the metabolic unit were transferred to the attention of COVID-19 patients.
We had to adapt our activity to the new conditions. In order to comply with government indications and to prevent the unnecessary exposure to the virus of our patients, live follow-up evaluations were suspended, and patients’ consultations were mainly done by phone or via email. Biochemical follow-up became a challenge. Metabolic control using filter paper samples in phenylketonuria has been established for decades. In recent years, measurements of phenylalanine, tyrosine and succinylacetone in tyrosinemia patients has become a common practice. Based on the good results for diagnosis of the neonatal screening programs, and our previous reported experience in long term follow up of propionic acidemia using filter paper samples instead of the usual liquid plasma or urine samples (15), we designed a model of remote monitoring for all our amino acid disorder patients. We report the results of this program from March to June 2020 for these patients, excluding those with PKU in which this is the usual process.