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Growth delay due to insulin-like growth factor type 1 deficiency
Growth delay due to insulin-like growth factor I deficiency is characterised by the association of intrauterine and postnatal growth retardation with sensorineural deafness and intellectual deficit.
ORPHA:73272Classification level: Disorder
The syndrome is extremely rare and only four cases have been reported in the literature so far.
Addition clinical features include microcephaly, adiposity, and insulin resistance. Partial gonadal dysfunction and osteoporosis may also be present. A case of partial IGF-I deficiency has also been described and was associated with pre- and postnatal growth retardation and microcephaly but the developmental delay was mild and hearing tests were normal.
IGF-I deficiency is caused by homozygous mutations in the insulin-like growth factor 1 gene (IGFI; 12q22-q24.1). IGF-I is essential for foetal and postnatal growth, brain development and metabolism.
Diagnosis relies on direct sequencing of the five IGF1 exons and of the intron-exon junctions. Measurement of IGF-I levels can be used for diagnosis but the circulating levels of IGF-I vary between patients (ranging from undetectable, low to very high) depending on the molecular defect present and on the immunoassay used.
The differential diagnosis should include growth hormone deficiency and growth hormone resistance (caused by GH receptor or STAT5b anomalies), growth delay due to insulin-like growth factor I resistance and primary acid-labile subunit (ALS) deficiency syndrome (see these terms), as well as secondary IGF-I deficiency due to nutritional problems.
Prenatal diagnosis is feasible for families with an identified IGF1 mutation proven to be responsible for the disease phenotype of intrauterine and postnatal growth delay associated with intellectual deficit.
IGF-I deficiency is transmitted as an autosomal recessive trait. Affected families should be offered genetic counselling and informed of a 25% risk of recurrence.
Management and treatment
Management involves nutritional and developmental support, together with screening for deafness. Growth velocity in patients with partial IGF-I deficiency can be increased by recombinant growth hormone (GH) therapy. Recombinant IGF-I therapy can be used in patients with complete IGF-I deficiency or those showing an insufficient response to recombinant GH treatment.