Paediatrics: Other forms of diabetes mellitus
Maturity onset diabetes of young (MODY), Neonatal diabetes mellitus, Cystic fibrosis-related diabetes (CFRD)
Other forms of diabetes mellitus
Maturity onset diabetes of young (MODY)
A clinical heterogeneous group of disorders characterized by an autosomal dominant mode of inheritance, onset usually before the age of 25yrs, and non-ketotic diabetes at presentation. The condition is due to a primary defect in B-cell function and insulin secretion. Six different types have been identified due to mutations in 6 different genes.
Neonatal diabetes mellitus
Rare (1/400 000–500 000 live births). Defined as hyperglycaemia requiring insulin therapy occurring in the first few weeks of life, transient (50–60%) and permanent forms are recognized.
- Transient neonatal diabetes mellitus (TNDM): a disorder of developmental insulin production that resolves spontaneously in the postnatal period. IUGR is evident at birth and FTT and hyperglycaemia occur in the first few days. Most patients will achieve remission and insulin independence within 1yr. However, in many, persistent diabetes recurs in late childhood/adulthood. TNDM is usually sporadic. Chromosome 6 abnormalities are observed in many (paternal duplications; paternal isodisomy; methylation defects).
- Permanent neonatal diabetes mellitus (PNDM): rare, and may be associated with a number of clinical syndromes (IPEX syndrome— diffuse autoimmunity; severe pancreatic hypoplasia associated with IPF-1 mutation; Walcott–Rallison syndrome).
- KCNJ11 related diabetes mellitus: activating mutations of the KCNJ11gene encoding the Kir62 subunit of pancreatic β-cell K+-AJP sensitive channels. Typically present in infancy and requires insulin initially. Later, treatment with oral sulphonylurea possible. Molecular genetic testing for this condition is recommended in all children with DM <1yr. This condition is associated with developmental delay and epilepsy in some cases (DEND syndrome).
Cystic fibrosis-related diabetes (CFRD)
The prevalence of CFRD increases with age (79% between ages 5 and 9yrs; 26% between ages 10 and 19yrs). It is primarily due to a defect in pancreatic insulin secretion, although modest insulin resistance is also recognized. Insulin is recommended for all patients with CFRD.
Severe insulin resistance syndromes
A rare, heterogeneous group of disorders. Genetic mutations resulting in insulin receptor and post-receptor signalling defects underlie the mechanism of severe insulin resistance. Hyperinsulinaemia is present. Common clinical features include acanthosis nigricans and evidence of ovarian hyperandrogenism in females. Syndromes associated with severe insulin resistance include:
- type A insulin resistance;
- Donohue’s syndrome;
- Rabson–Mendenhal syndrome;