Holocarboxylase Synthetase Deficiency (HLCS)
Holocarboxylase synthetase deficiency is an autosomal recessive disorder caused by pathogenic variants in the gene HLCS, and although it is considered to be a pan-ethnic disorder, it is most commonly seen among those of Faroese and Asian descent. Affected individuals will usually present with symptoms before three months of age, which include feeding difficulties, breathing problems, skin rash, hair loss, and lack of energy. Untreated individuals can progress and experience developmental delay, seizures, coma, and eventually death during childhood. Treatment with biotin supplements is generally effective and potentially capable of reversing certain disease side effects, making the prognosis of the disease favorable. Certain aspects of disease severity and response to treatment may be predicted in some cases based on the inherited variants.
For information about carrier frequency and residual risk, please see the residual risk table.