Monogenic diabetes and neonatal diabetes — branching viva

Branch 1 — The six-week-old with persistent hyperglycaemia

Stage 1. A six-week-old, small for gestational age, has persistent insulin-requiring hyperglycaemia found during a febrile illness. What is the diagnostic principle that governs any diabetes at this age? ^[1]

Diabetes under six months is almost never autoimmune type 1, so the working diagnosis is monogenic neonatal diabetes until a genetic test says otherwise; the work-up is molecular, not antibody-based. ^[1]

Stage 2 (release). The baby has mild developmental delay and hypotonia. Which gene group rises up your differential, and what is the clinical syndrome called? ^{[2] [5]}

The combination of neonatal diabetes with developmental delay and hypotonia points to an activating KCNJ11 or ABCC8 potassium-channel mutation with a DEND syndrome (developmental delay, epilepsy and neonatal diabetes). ^{[2] [5]}

Stage 3 (release). The panel confirms an activating KCNJ11 mutation. How does this change the treatment and why does it work? ^[3]

The child is switched from insulin to oral glibenclamide. The activating mutation holds the KATP channel open so the beta cell cannot depolarise; a sulfonylurea closes the channel directly, bypassing the faulty ATP-sensing step and restoring insulin release, which usually improves both glycaemia and the neurological features. ^[3]