Iron is one unsung hero in our body. Apart from oxygen transport, it plays a vital role in constituting important enzymes as well as some detoxification reactions and also in converting sugars into energy.
But, during infections,the same iron stored in our body can prove lethal. It has been studied that bacteria use our very own iron stores to launch a full scale attack. That is why, intracellular bacteria like Mycobacteriae which use iron repositories in macrophages can cause so much damage.
It has been observed that a certain Somalian population, despite being anaemic was resistant to diseases like malaria, tuberculosis and so on. When doctors prescribed iron supplements, infections gained an upper hand. Actually, the population wasn't facing the infection despite the anaemia, but because of it!
Going by this, wouldn't patients with hemochromatosis be a playground for bacteria?
No!
Let me explain. Patients of hemochromatosis also have an another mutation, C282Y on HFE gene. This results into decreased levels of the C282Y protein, resulting into increased sensitivity of the WBCs to the chelator, transferrin resulting further into bacteria being unable to use iron as it remains 'locked' away at sites rather inaccessible to them.
Where does plague come into this?
It is being thought that when plague was rampaging through Europe, population with hemochromatosis was rather resistant and hence the gene for the disease was selected. This is why people of northern and western European descent have a higher prevalence of hemochromatosis.
Thursday, February 26, 2015
Of Iron, bacteria, hemochromatosis and plague
Study group discussion: Shift to left
Would someone tell me what exactly is 'shift to left' in WBCs?
The production of immature cells... And release of them in circulation.
If you draw the stages of white blood cells from left to right, becoming more mature.. Shift to left would mean immature WBC's have been released into circulation.
Woah. Didn't know it.
Oh, thanks! Had this query since second year! :D
In which conditions do we get a left shift?
Infection, inflammation, leukemia.
Which leukemia? Acute or chronic? Myeloid or lymphoid?
I think it's fair to say it occurs in all leukemias.. I couldn't find a reliable resource online on the same.
Study group experience #12
Monday, February 23, 2015
Abnormal breath sounds: Crackles, Wheeze, Rhonchi and Stridor
Crackles (Also Known as Rales)
What do crackles sound like?
Roll your hair between your fingers next to your ear.. That's what fine crackles sound like! (Or the sound of salt heated on a frying pan, if you've ever tried cooking :P)
Coarse crackles sound like ripping open Velcro.
When are crackles heard?
Crackles are much more common during the inspiratory than the expiratory phase of breathing, but they may be heard during the expiratory phase.
Mechanism of crackles:
Crackles are the sounds you will hear in a lung field that has fluid in the small airways or if atelectasis is present.
Causes of crackles:
Crackles is often a sign of adult respiratory distress syndrome, early congestive heart failure, asthma, and pulmonary edema.
Rhonchi
What do Rhonchi sound like?
Try making a snoring sound or try to make a sound as if you're gargling your mouth. That's what Rhonchi sounds like!
When are Rhonchi heard?
Rhonchi are more prominent on exhalation.
Mechanism of Rhonchi:
Secretions in large airways, as occurs with bronchitis, may produce these sounds; they may clear somewhat with coughing.
Causes of Rhonchi:
Pneumonia, chronic bronchitis, and cystic fibrosis are patient populations that commonly present with rhonchi.
Wheezes
What do wheezes sound like?
Try whistling slowly while exhaling.. That's what wheezes sounds like! Wheezes are continuous musical tones.
When do wheezes occur?
Wheezes are most commonly heard at end inspiration or early expiration.
Mechanism of wheeze:
As the airway lumen becomes smaller, the air flow velocity increases resulting in harmonic vibration of the airway wall and thus the musical tonal quality. They result as a collapsed airway lumen gradually opens during inspiration or gradually closes during expiration.
Causes of wheezes:
Heard when listening to an asthmatic patient. Sibilant wheezes are caused by asthma, congestive heart failure, chronic bronchitis, and COPD too.
PS: Wheeze is also known as sibilant rhonchi.
Rhonchi is also known as sonorous wheeze.
Stridor
What does stridor sound like?
Stridor are intense, high-pitched, continuous monophonic wheezes (musical sound) heard loudest over extrathoracic airways. Similar to a creaking or a grating sound.
When is stridor heard?
They tend to be accentuated during inspiration when extrathoracic airways collapse due to lower internal lumen pressure.
Mechanism of stridor:
It usually caused by a foreign body obstruction of the larger airways, such as the trachea or a main bronchus.
Causes of stridor:
It is also the most common type of breath sound heard in children with croup (Laryngotracheobronchitis caused by parainfluenza) and a foreign body airway obstruction.
Also heard in Bacterial tracheitis, Diphtheria, Epiglottitis (H. Influenza) and Broncholitis (RSV).
Stertor
What is Stertor?
It is like stridor but it's more harsh, less musical and low pitched.
Mechanism of stertor: Respiratory sound that originates from pharynx, basically, anywhere above larynx.
Causes of stertor: Seen in partial obstruction of airway above larynx characterised by heavy snoring and gasping like in obstructive sleep apnea.
Thanks Nab, for explaining stertor to me!
Sunday, February 22, 2015
Study group discussion: Radiological findings in meningioma
A 36-years-old female has been complaining of recurrent headaches since four months. On examination, she has papilledema. MRI of brain showed an extra-axial, dural based and enhancing lesion in frontoparietal region with positive ‘dural tail’ sign. Diagnosis?
The dural tail sign occurs as a result of thickening of the dura. It's meningioma..
Other sign associated with meningioma is the mother in law sign..
The mother in law sign is perhaps uncharitably (depends on the mother in law I suppose) used to describe lesions that enhance early during the arterial phase and remain opacified well after the venous phase. The joke is that a mother in law comes early and stays late.
It is most frequently equated with the angiographic appearance of a meningioma.
Study group discussion: To anticoagulate or to not anticoagulate
One quick review question:
So patient has new onset atrial fibrillation. Would you start the anticoagulation right away?
Its only after 48 hrs of onset, that too you have to rule out intra-atrial thrombus by trans esophageal endoscopy. If the thrombus is present, you give heparin.
Yeah when there is thrombus that's a must! But let's say no thrombus now what? 35 yrs old male. Can we start anticoagulants?
There is specific criteria. For assessment of thromboembolic risk. It's called CHADS2.
Oh yes, if the score is >=1 then you start it. One point each for CHF, HTN, age >75, diabetes and 2 points for prior stroke or TIA.
If patients have not been adequately anticoagulated and the AF is more than 24–48 h in duration, a transesophageal echocardiogram (TEE) can be performed to exclude the presence of a left atrial thrombus that might dislodge with the attempted restoration of sinus rhythm with either nonpharmacologic or pharmacologic therapy.
It can be a different scenario!
* In the case I was discussing above the AF resolved soon after metoprolol.
And in that case anticoagulation are started as prophylaxis. So would be oral warfarin or the LMWHs.
Study group discussion: Charcot's in Medicine
I read about charcot and who knows the conditions, name of diseases starting with charcot?
Charcot Leyden crystals - Eosinophils in sputum of patients with allergic diseases.
Then charcot joint too.. In diabetes, syphilis. Neuropathic joints, basically.
Charcot triad is of which condition?
One is of infection of gallbladder - Jaundice, fever, right hypochondriac region pain.
Charcot's triad in multiple sclerosis is sin - Speech disturbance, intention tremors, nystagmus!
I thought intention tremors were characteristic of cerebellar disease.
Exactly but seen in MS though not pathognomonic.
More charcots?
Charcots disease is ALS.. Amyotrophic lateral sclerosis !
The ice bucket challenge one. It's other name is based on some famous baseball player, right? Lou Gehrigs disease!
Charcot's artery?
Lenticulostriate artery!
The ones responsible for lenticular infarcts? There are five types, right?
Pure motor, pure sensory, clumsy hand, ataxia and sensorimotor!
Charcot bouchard aneurysms!
Charcot marie tooth disease !
Charcot wilbrand syndrome- visual agnosia!
Nice one! Keep learning and sharing :D
Study group discussion: Pathogenesis of symptoms in glucagonoma
Why does glucagonoma cause dermatitis and DVT?
The exact cause isnt known, but one of the reasons may be, because the excess glucagon produced reduces the amount of albumin (which carries Zinc) hence producing a relative deficiency of Zinc. The similar type of which is also found in Zn deficiency. And hence, the dermal manifestation!
The dermal manifestation is called NME - Necrolytic Migratory Erythema
That was one of my MCQ! Also glucagonoma is the commonest type pancreatic tumours to occur in MEN 1 syndrome.
And deep vein thrombosis?
The mechanism for the coagulopathy is poorly understood and seems to be related to an increased factor X production by the pancreatic alpha-cells.
Anyone would like to name the 4 D's of glucagonoma?
Diabetes
Dermatitis (rash),
Deep vein thrombosis (e.g., blood clot in the legs)
Depression
Study group discussion: Can a child less than 6 months be given anything other than breast milk?
Hello. I had this little doubt, I'm in the second year and haven't been exposed to paeds yet. So...
Do you give a child below six months anything other than breast milk? If no, then what do you do if a mother isn't producing enough milk and the baby is still hungry?
What I learned in peds (only did one of three semesters so far) it's that there's very very rare for the mother to not produce enough milk. most of the times is a matter of wrong breast feeding technique.
But formulas can be used, if in the right proportion of formula to water. Or even cow milk, but it also has a specific recipe to dilute it.
I'm not sure. It's probably not recommended as the milk will be different from the mother's.
You can use fórmulas, you can't give them cow Milk until they are one year old.
I learned that if the family can't afford formulas is ok to give cow milk since the birth. It has to be diluted with water and added some sugar and a drop of soy oil to make it more similar to breast milk.
It is possible that sometimes a woman other than the mother can breastfeed too.
In my peads wards, I have seen mothers giving top feeds with the not enough milk production excuse.
If the child doesn't have a mother, I think they're provided with diluted cows milk or infant formulas.
The only reason it isn't recommended in infants who have mothers who can feed their child is because they have nipple confusion / detachment and they won't consume the mothers milk anymore (Which is super important for the baby, since they have antibodies!)
Study group discussion: Krukenberg in Medicine
Krukenberg tumor?
Krukenberg procedure?
Krukenberg spindle?
Study group discussion: Mifepristone
Major use of mifepristone in obstetrics gynaecology is?
A) ectopic pregnancy
B) molar pregnancy
C) fibroid uterus
D) threatened abortion
A??
Yes, it's A. Please explain.
Mifepristone is abortifacient. It causes abortion by blocking progesterone.
But what if the ectopic site is not in connection with the uterine lumen. How will it be aborted?
I guess progesterone level in required to maintain the implantation.. A decrease in progesterone will cause it ectopic pregnancy to abort from that place.
That's right.
Mifepristone is also sometimes used to end pregnancies when more than 49 days have passed since the woman's last menstrual period; as an emergency contraceptive after unprotected sexual intercourse ('morning-after pill'); to treat tumors of the brain, endometriosis (growth of uterus tissue outside the uterus), or fibroids (noncancerous tumors in the uterus); or to induce labor (to help start the birth process in a pregnant woman).
Rh incompatibility USMLE Step 2 CK doubt
If the patient is sensitized and is making Rh antibody, there is no point giving, Rhogam right?
Nope. It is only for prevention to Rh sensitisation. It's not the treatment.
I see!
So once she is sensitized, nothing can be done?
Nope.
So, say there is a mother who had a kid with hemolytic disease last pregnancy. Will I be giving her Rhogam next pregnancy?
No.
You monitor the Rh antibody levels (by titres using indirect antiglobulin test).
If >1:4 woman is considered sensitized.
If >1:16 do the spectrometric test by using fetal cells taken by amniocentesis (To monitor bilirubin levels!)
Bilirubin low: Repeat amniocentesis in 2-3 weeks.
Bilirubin high: Measure hematocrit of baby using percutaneous umbilical blood sampling.
If the baby is affected (Fetal hematocrit low), only treatment is to give blood transfusion to the baby in utero (Intrauterine transfusion) And delivery at 37 weeks. Or even earlier.
Ooh. I get it all now <3
Study group discussion: Drugs and conditions that enhance Digoxin toxicity and the mechanism behind it
So if you have SVT in digoxin toxicity.. Would you give verapamil?