A technical term, not just a fever without obvious source! Essentially presence of confirmed fever for 8 days or more in a child in whom a careful thorough history and physical examination, and preliminary laboratory data fail to reveal a probable cause.
Long list of possible causes, long lists of possible tests – do thorough history and repeated examinations, then follow the clues!
In kids, infection is the commonest cause. But can be connective tissue disorder, or malignancy.
Beware factitious fever – admission sensible.
If possible, stop all drugs. Antipyretics may obscure the pattern of fever, and can occasionally be its cause (drug fever is one cause).
Unless the child is critically ill, try not to give antibiotics. If the diagnosis remains obscure, go back and take the history again, examine the child (fully) again, send the specimens again!
Abnormal renal excretion, leading to low potassium.
Presents in early childhood with failure to thrive. Could also be constipation, muscle cramps and weakness (potassium needed for membrane potential, so these are all neuromuscular) and non-specific dizziness and fatigue.
Characteristic hypokalemic, hypochloremic metabolic alkalosis. High plasma renin activity and high aldosterone concentration seen.
Gitelman syndrome is similar, less severe (distal tubule, rather than ascending limb of loop of Henle) – less failure to thrive, in fact often asymptomatic detected incidentally. Might present with nocturia/polyuria.
Urinary calcium excretion distinguishes the two syndromes. Bartter’s waste calcium (more severe, after all), Gitelman retain.
Treatment is with supplementation.
Decompensation can be precipitated by diarrhoea or vomiting. Acute treatment can include potassium-sparing diuretics (spironolactone), cyclo-oxygenase inhibitors and renin-angiotensin blockers.
Proteins responsible for a minority of allergic reactions to peanut, hazelnut, sesame among others – hydrophobic, so tend not to be well represented in skin prick and IgE test solutions. May explain false negatives.
Specific IgE tests have been developed, but otherwise you just have to challenge.
Dutch study however didn’t find that specific testing for oleosins helped much.
FMR1 gene is on X chromosome, obviously, and is a trinucleotide repeat disorder (along with Friedrich’s ataxia, myotonic dystrophy, Huntington disease etc), so inheritance is interesting.
Dads can carry gene, but only pass it on to their daughters (who will all get it).
Mums will carry gene on 1 chromosome, so sons and daughters can both get it, but 50:50 chance.
As with other trinucleotide repeat disorders, gene expands with each generation, so risk of disease increases from 1 generation to the next, and this is somewhat predictable: intermediate gene (so 45-54 copies) won’t expand to cause disease (200+ copies) in 1 generation, but premutation gene (55-199) copies probably will.
Moderately severe learning disability
Facial features – long face, midface hypoplasia, large lips and jaw, small ears