Methylmalonic and propionic acidaemias are rare metabolic disorders with an autosomal recessive mode of inheritance. A number of aminoacidopathies may have cutaneous manifestations, but these are usually absent in methylmalonic and propionic acidaemia. We have studied 38 children with propionic and methylmalonic acidaemia in the last 10 years at the Hôpital Necker-Enfants Malades. Thirteen had cutaneous manifestations: acute superficial scalded skin and superficial desquamation, bilateral and periorificial dermatitis, psoriasiform eruptions, and alopecia. The relative uniformity of these manifestations (scalded skin and desquamation after metabolic decompensation, chronic bilateral and periorificial dermatitis) suggests that methylmalonic and propionic acidaemias should be included in the category of aminoacidopathies with cutaneous manifestations. All these patients were suffering from severe forms of these diseases, with no residual enzyme activity, and they were all subjected to a very severe natural protein-restricted diet. These cutaneous manifestations may therefore either be part of a complex multideficiency syndrome, or be due to the enzyme deficiency itself.