Methylmalonic acidemia (MMA) is an autosomal recessive genetic disorder caused by decreased activity of methylmalonyl‐CoA mutase or metabolic disturbance of its coenzyme cobalamin, cutaneous manifestations are rare clinical signs in this disease. Herein, we describe a Chinese boy with MMA fed with a formula lacking branched‐chain amino acids presenting with erythroderma and acrodermatitis enteropathica‐like rash, a homozygous nonsense mutation c.742C>T (p.Gln248*) was identified in the MMAA gene. The pedigree exhibited a non‐Mendelian inheritance pattern which was attributed to maternal uniparental disomy on chromosome 4q26‐q34.1 of the proband, confirmed by chromosomal microarray analysis. Our case highlights the association between skin changes and nutritional deficiency due to therapeutic amino acid restrictions in MMA.

Enterokinase deficiency (EKD) is a rare autosomal recessive inherited disorder caused by loss‐of‐function mutations of the transmembrane protease serine 15 (TMPRSS15) gene. To date, only 12 cases of EKD have been described in the literature and skin involvement has seldom been described. We identified a novel homozygous nonsense mutation in the TMPRSS15 gene (c.1216C>T, p.R406*) in a female infant, who manifested with acrodermatitis enteropathica (AE)‐like lesions that were dramatically relieved within 11 days after initiation of a protein‐rich hydrolyzed formula. Our case shows that AE‐like rashes can be a manifestation of EKD and expands the spectrum of causative mutations in the TMPRSS15 gene.