Deficiency Multiple Carboxylase Late Onset, also known as late-onset multiple carboxylase deficiency (LOMCD), is a rare metabolic disorder characterized by the inability to properly metabolize certain proteins, fats, and carbohydrates due to a deficiency of biotin. Synonyms for this condition include biotinidase deficiency, biocytinase deficiency, and holocarboxylase synthetase deficiency. These terms are used interchangeably to describe the same underlying condition. LOMCD typically manifests later in life, leading to symptoms such as lethargy, poor appetite, hair loss, neurological issues, and skin rashes. Early diagnosis and management are crucial in order to prevent serious complications. Individuals with LOMCD require lifelong biotin supplementation to support their metabolic needs.