Adrenal hyperplasia is a rare genetic condition that involves the adrenal glands, which lie just above the kidneys.
It results in a blockage in the assembly line that makes the stress hormone cortisol from its chemical precursors.
People with the condition have low levels of cortisol, which helps to regulate blood sugar levels. If they fall too low, it can result in a coma.
But in some cases, the blockage can also reduce the production of aldosterone, a hormone involved in the regulation of salt in the bloodstream.
If salt levels fall too low it can lead to dehydration, vomiting and death.
Regular treatment with steroid medicines can help to maintain normal hormone levels and although the condition is lifelong, the outlook is generally good.
But Malakhi is now likely to have missed two doses of his medication and there is increasing concern for his welfare.