Acrodermatitis dysmetabolica as a sign of methylmalonic aciduria decompensation

Acrodermatitis dysmetabolica secondary to isoleucine deficiency in infant with maple syrup urine disease

Acrodermatitis dysmetabolica (AD) describes eruptions characterized by the clinical triad of acral dermatitis, diarrhea, and alopecia. AD can be caused by various metabolic disorders, one of which is maple syrup urine disease (MSUD). We present a 2- month-old boy diagnosed with MSUD by the age of 5 days and treated with branched-chain amino acid (BCAA) restricted diet, BCAAs formula, and thiamine supplementation. He was referred to dermatology with a 3-week history of diarrhea, progressive acrodermatitis enteropathica like cutaneous eruption and hair loss over the scalp treated with topical mometasone ointment, isoleucine supplementation and leucine restriction. Complete resolution of skin eruption was achieved by 4 weeks, which correlates with normalization of BCAA levels based on close monitoring of biochemical lab values and growth. This case emphasizes the dangers of limiting BCAA intake when treating MSUD, as well as the importance of close monitoring during the amino acid depleting period of growth.

Immunometabolism – The Role of Branched-Chain Amino Acids

Immunometabolism has been the focus of extensive research over the last years, especially in terms of augmenting anti-tumor immune responses. Regulatory T cells (Tregs) are a subset of CD4⁺ T cells, which have been known for their immunosuppressive roles in various conditions including anti-tumor immune responses. Even though several studies aimed to target Tregs in the tumor microenvironment (TME), such approaches generally result in the inhibition of the Tregs non-specifically, which may cause immunopathologies such as autoimmunity. Therefore, specifically targeting the Tregs in the TME would be vital in terms of achieving a successful and specific treatment. Recently, an association between Tregs and isoleucine, which represents one type of branched-chain amino acids (BCAAs), has been demonstrated. The presence of isoleucine seems to affect majorly Tregs, rather than conventional T cells. Considering the fact that Tregs bear several distinct metabolic features in the TME, targeting their immunometabolic pathways may be a rational approach. In this Review, we provide a general overview on the potential distinct metabolic features of T cells, especially focusing on BCAAs in Tregs as well as in their subtypes.

Pathophysiology of propionic and methylmalonic acidemias. Part 1: Complications

Over the last decades, advances in clinical care for patients suffering from propionic acidemia (PA) and isolated methylmalonic acidemia (MMA) have resulted in improved survival. These advances were possible thanks to new pathophysiological insights. However, patients may still suffer from devastating complications which largely determine the unsatisfying overall outcome. To optimize our treatment strategies, better insight in the pathophysiology of complications is needed. Here, we perform a systematic data-analysis of cohort studies and case-reports on PA and MMA. For each of the prevalent and rare complications, we summarize the current hypotheses and evidence for the underlying pathophysiology of that complication. A common hypothesis on pathophysiology of many of these complications is that mitochondrial impairment plays a major role. Assuming that complications in which mitochondrial impairment may play a role are overrepresented in monogenic mitochondrial diseases and, conversely, that complications in which mitochondrial impairment does not play a role are underrepresented in mitochondrial disease, we studied the occurrence of the complications in PA and MMA in mitochondrial and other monogenic diseases, using data provided by the Human Phenotype Ontology. Lastly, we combined this with evidence from literature to draw conclusions on the possible role of mitochondrial impairment in each complication. Altogether, this review provides a comprehensive overview on what we, to date, do and do not understand about pathophysiology of complications occurring in PA and MMA and about the role of mitochondrial impairment herein.