What is Holocarboxylase Synthetase Deficiency?

Holocarboxylase synthetase deficiency is a treatable inherited disease in which the body is unable to use the vitamin biotin effectively. If left untreated, the disease can cause numerous complications. The signs and symptoms of HCLSD typically appear within the first few months of life, although the age of onset can vary. Affected infants often have difficulty feeding, breathing problems, skin rash, hair loss, and a lack of energy. It can also lead to delayed development, seizures, and coma. These medical problems may be life-threatening in some cases.

How common is Holocarboxylase Synthetase Deficiency?

Holocarboxylase synthetase deficiency is estimated to affect between 1 in 87,000 to 1 in 100,000 people worldwide. The occurrence is higher for individuals of Scandinavian descent, with rates as high as 1 in 1,200 people from the Faroe Islands. Certain mutations are also believed to be relatively common among the Japanese population.

How is Holocarboxylase Synthetase Deficiency treated?

In most cases, biotin is the only required treatment for holocarboxylase synthetase deficiency, and affected individuals do not need to modify their diet or activity due to this condition. By taking daily supplements of biotin before symptoms occur, all symptoms of the disease can be avoided. If treatment begins after symptoms appear, some symptoms, such as skin problems and hair loss, will disappear; however, irreversible developmental deficits are possible and may require assistance from learning specialists.

Biotin supplements must be taken by mouth throughout life. This treatment is highly effective, provided a physician determines the proper dosage of biotin and adjusts that dosage over time if necessary.

What is the prognosis for a person with Holocarboxylase Synthetase Deficiency?

Early detection and treatment with biotin supplementation may prevent, manage, and possibly reverse symptoms. With treatment, most affected individuals are expected to have normal growth and development, although some individuals may have lifelong learning problems. Without treatment, holocarboxylase synthetase deficiency can be life-threatening.

Other names for
holocarboxylase synthetase deficiency

  • Early-onset multiple carboxylase deficiency
  • HLCS Deficiency
  • Holocarboxylase deficiency
  • MCD
  • Multiple carboxylase deficiency
  • Multiple co-A carboxylase deficiency
  • Neonatal form of multiple carboxylase deficiency


  • Genetics Home Reference, 2007, http://ghr.nlm.nih.gov/condition/holocarboxylase-synthetase-deficiency
  • Hui et al., 2012, World J Pediatr, 8(3):278-80, PMID: 21874615
  • Lund et al., 2007, J Inherit Metab Dis, 30(3):341-9, PMID: 17417720
  • O'Neill et al., 2005, http://omim.org/entry/253270
  • Suzuki et al., 2005, Hum Mutat, 26(4):285-90, PMID: 16134170