you're on your peds round today. first patient on the roll has a gene defect where he can't make myeoloperoxidase and this is the cause of his recurrent infections. do you know why myeloperoxidase is essential? what mechanism does this boy lack and therefor is susceptible to infections?
his immune cells can't engage in respiratory bursts. myeloperoxidase catalyzes the conversion of H2O2 and chloride ions into hypochlorus acid, which is 50 times more potent at killing microbes than H2O2 alone. so the boy's neutrophils are weakened.
next patient to come in: he's just like the previous patient...has recurrent infections, BUT this time the defect is in microtubules and phagocytosis. he has severe gingivitis and oral mucosa ulceration and albinism.
your patient has CHEDIAK HIGASHI disease (not too common, but we are talking immunodeficiencies today). kid will have strep and staph infections. you prescribe acyclovir (which i know, is an antiviral...but acyclovir boosts recovery and fights off viruses). the globins you'd later transfuse will deal with the strep and staph. remember: mouth stuff, recurrent infections, hypopigmentation: chediak higashi!
right then. you want your coffee break, but another patient gets sent to you. he has recurrent bronchopulmonary infections (bacterial), thymus aplasia, telengiectasias, growth retardation and you noticed when he walked in, he sort of waddled more than walk.
kid has? *drum roll*
ATAXIA TELEANGECTASIA! both B and T cells aren't functioning. his alpha fetoproteins will ALWAYS be high. keyword here: ataxia (waddling).
you beg the nurse to let you off, but she's already got the patient into the room. this time you got a little dude, 2 years old. you look at the chart and see that he has had lots of bacterial and fungal infections and his mum says the white stuff has come again. what does the kid have? what is the white stuff the mum's talking about?
little dude has severe combined immunodeficiency aka SCID. the white stuff is candida. kid will have IL-2 deficiency. you must start TMP-SMX prophylaxis for pneumocystis carinii (it's called something else now...change in nomenclature...pneumocystis jiroveci!) coz kids with SCID usually die from this infection.
so, you think you'd sneak out for that coffee, but you prolly know the story by now. yet another kid walks in with an immunodeficiency. the kid has increased reflexes, you think his face looks abnormal, you notice he has a congenital heart disease, labs says he's hypocalcemic and CXR shows no thymus...where did it go?!
the child has DiGeorge's disease aka thymic aplasia. his 3rd and 4th arch failed to developed. problem with parathyroid gland as well...hence hypocalcemia.
you stretch, thinking you've had enough of kids with immunodeficiencies but your day has only just begun. another kid comes in with his mum. he has recurrent otitis media, eczema and thrombocytopenia from strep pneumonia. his IgM is low and he bleeds easily. what's the Dx?
he has XLR wiskott-aldrich syndrome! there's a tendency to get infections from capsulated bugs like strep pneumonia (have you read my post on capsulated bugs? if you haven't, here it is). kid will have LOW IgM, HIGH IgA (which sort of makes up for the low IgM so he's not as bad as the kid with SCID...all he needs is amoxicillin or ceftriaxone). so remember: attacks from capsulated bugs, BLEEDING, otitis media, eczema = wiskott-aldrich syndrome.
you thought you hit gold for getting all those Dx right, but another kid comes in. you grumble, but you remember you took the oath and sold your soul to saving lives (doesn't that just warm you up inside?), so you grab the patients chart and go see her. yeah, let's make this kid a female one, aight. you palpate her lymph nodes and notice she has lymphadenopathy. her liver is palpable too (hepatomegaly). she's tiny for her age (growth retardation) and looks like she has chronic skin infections. you suspect something's up with her phagocytes (hint! hint!) and sent her sputum for culture. it comes back positive for Aspergillus. you know for sure now, that she has?
CHRONIC GRANULOMATOUS DISEASE! granulomas are the skin stuff she has (recurrent skin infections) and key points: Aspergillosis and phagocyte deficiency!
you say goodbye to the little girl and just as she leaves, a guy pushes his kid in. "doctor! my kid has wiskott-aldrich syndrome!". you cock your eyebrow at him, get a little annoyed everyone has access to webMD and google, but don't show this to him of course (ethics!). the dad goes on to explain that he was talking to this lady in the waiting room and her kid was diagnosed with wiskott-aldrich syndrome and he has the same symptoms as the dude's son. of course you can't take the dad's word for it and proceed to examine the kid yourself. you find that he has recurrent infections yes, diarrhea sometimes. has low IgG. and his B cells lack CD19. does he have wiskott-aldrich?
nope. kid has Bruton's agammaglobulinemia (aka X-linked agammaglbulinemia...X-linked meaning boys are affected more often). very similiar to wiskott-aldrich (also X-linked), BUT remember the key point for wiskott aldrich was BLEEDING! this kid doesn't have that. he has a problem with his B cells, coz he has a defect in the Bruton's tyrosine kinase gene (Btk gene) which means he has a defect in B cells developement (they can't mature). kid has the same susceptibility to encapsulated organisms (seriously, read that post on capsulated bacteria! it will help you), with recurrent otitis media, eczema and other bacterial infections. treatment would just be transfusing Igs.
so you give yourself a pat on the back, crick your neck muscles and are about to call it a day, but the nurse promises you, 'just one more!', so you be the good guy (or gal) and say, 'bring it on!'. this kid comes in. just like the others, he has recurrent infections, BUT his are limited to sinopulmonary infections (bacterial). he's older than most of the other kids you saw today and is pretty asymptomatic otherwise. oh, and he tells you, he almost always has diarrhea. i've technically just given you the diagnosis. what is it?
IgA deficiency. his IgG and neutrophils would be normal, but he has a problem with local immunity (nasopharynx and small intestine, remember please that IgA's found in these places).
TADA. what a day, eh? are you rocking internal medicine or what? =)
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