T cells disorders

Hi everyone, today we are going to explain about the “soldiers”, do u remember? the T cells.

 So, in this topic we will talk about the most well know T cell disorder: DiGeorge syndrome, also known as velo-cardio-facial syndrome, Shprintzen syndrome,conotruncal anomaly face syndrome, Strong syndrome, congenital thymic aplasia, and thymic hypoplasia (For the USMLE purpose DiGeorge is fine, Dr. DiGeorge described this syndrome in 1968).

 This is a congenital disorder due to a deletion in chromosome 22 (22q11.2, this is the long arm of the chromosome). The patients will present hypoplasia or aplasia of thymus and parathyroids (remember that the problem here is in the 3th and 4th pharyngeal pouches)

 

 

In this case there is increase risk for opportunistic infections (remember we don’t have our “soldiers”), so patients can present with fungi and viruses early in life.

 To remember the features of the syndrome we have the nmenomic: CATCH – 22, where 22 is to remember the chromosome number, so here we go: C for cardiac abnormalities (Fallot), A stands for abnormal facies, T stands for thymic aplasia (hypoplasia), C stands for cleft palate and finally H stands for hypocalcemia and hypothyroidism, 

 C: cardiac

A: abnormal facies

T: thymic aplasia

C: cleft palate

H: hypocalcemia, hypothyroidism

 

Now in some cases the hypocalcemia might be helpful in the diagnosis, because sometimes the only presentation in a neonate are seizures (due to hypocalcemia). Other Lab findings include: decrease lymphocytes (with decrease CD3+ which is the marker for the T cells), and a normal level of immunoglobulins (remember that B cells are normal here)

Also a important thing to remember (and always asked) is the association of DiGeorge and the increase risk (up to 20 to 30 times) to develop schizophrenia. 

For the treatment we have to treat based on each case, if the patient have cardiac abnormalities, he might require cardiac surgery, if he is having infections he might need antibiotics or antifungals, for the hypocalcemia or hypothyroidism the patient may need vitamin D and calcium supplement, and in rares cases (of fully thymic aplasia) the patient may require thymic transplant.

So in summary, remember the chromosome number (22), the presentation (CATCH), the lab findings (hypocalcemia and hypothyroidism) and the association with schizophrenia.

The next topic will be about phagocytic system disorders, 

Hope you enjoy the reading,

See you on the next post

 

Carlos Albrecht

B cells disorders

Remember about the factories? well now we will explain the B cells disorders.

 In general in this kind of deficiencies, we will have increase risk of recurrent infections with encapsulated bacterias, enteroviral, hepatitis viruses and sinopulmonary infections. They have in common in the physical exam that this will be normal (that means no increase in size of tonsils, nodes). And in the history we will have a patient who is healthy until he is around 6 to 9 months old, when he presents with recurrent infections as we said before.

 Knowing this, here we go:

 1. Bruton Agammaglobulinemia (also know as X-linked agammablobulinemia)

 Ok, let’s start from the name: A – gammaglobulinemia, “A” means lack, so in this case we will have a lack or absence of B cells and therefore we will have in the laboratory findings very low levels of Ig G,A,M,E (GAME) This means decrease CD19+ which is the marker for B cells, BUT having normal levels of T cells with their marker CD3+.

 Treatment: regular use of what we lack: Ig, so we will give IVIG (intravenous immunoglobulin)

 2. CVID (a.k.a. common variable immunodeficiency)

 The main issue in this disorder is that even having a NORMAL number of B cells, they don’t produce the amounts of Ig needed. So again in common with the B cell disorder our risk of having recurrent infections will increase. One specific characteristic of this disorder is the increase risk of autoimmune disorders like pernicious anemia and seronegatives diseases, and also the increase risk of lymphoma specially in females.

 Treatment: again is using IVIG, but prior to this we will need to make screening for anti-IgA antibodies, if they are present is safer to use IVIG without IgA.

 3. Selective IgA deficiency

Do we have to say more about this? Well yes. Obviously we will have a selective deficiency of IgA, this will increase the risk of respiratory and GI infections, like Giardia (remember where do we have IgA). But also this will have a increased risk of anaphylaxis in those who receive blood from a person with normal level of IgA and a increase risk of autoimmune disorders like in CVID.

Treatment: this one will have a different one, DON’T USE IVIG, why? because of the increase risk of anaphylaxis from anti-IgA antibodies, plus IVIG is almost 100% IgG. So just treat the infections as they appear.

So in summary:

Bruton: absence of B cells (low level of Ig), treated with IVIG

CVID: normal number of B cells with defective production of Ig (low level of Ig), lymphoma associated and treated with IVIG (screening for antiIgA needed prior to treatment)

Selective IgA Def: normal number of B cells with defective production of IgA, anaphylaxis with blood from normal patient, DON’T USE IVIG (again risk of anaphylaxis)

This is all for today, I hope you enjoy the lesson

See you on the next post: T cells disorders

Carlos Albrecht

Immune diseases…an overview

This topic is very important but very confusing as well, I will try to explain in the next for four post, but first lets make an overview about it.

In the defense of our bodies we have “soldiers” that fight for us, we have several types, today we will review about four of them, B cells, T cells, phagocytic system and complement system.

B cells: think about this cells as factories, this cells will produces immunoglobulins (or antibodies) against antigens. They work in the humoral defense of the body.

T cells: this cells will be like the workers, the can be divided in different types like helper, cytotoxic and memory. They work in the cell-mediated defense of the body.

Phagocytic system: think about hungry dudes looking for food, basically are monocytes and macrophages.

And finally we have the complement system: as the name says, they complement the work of the other workers. They are part of the innate immune system, they attack following a cascade increasing their response creating what’s known as MAC (membrane attack complex).

Keep this information in mind because we will need this basic knowledge for the next topics.

See you in the next post.

Carlos Albrecht

Abdominal Wall Defects

The first topic we are going to review today are the abdominal wall defects.

So, we have first umbilical hernia, think of a weak portion in the belly and like a small mass protruding out of it. For this we have to think about number 4, what does it mean? If the hernia is less than 4 cm in size and doesn’t have symptoms, we can just keep doing clinical follow up of the kid, but if even being less than 4 cm it present symptoms (like pain) this kid might need surgery. Again number 4, umbilical hernias, usually have to disappear by the age of…yes you did it right by the age of 4. But if we have a kid over 4 years old still with the hernia present, he also might need surgery because of the risk on increasing in size.

The next defect is called omphalocele, this word has Greek origin, where they called Omphalo to the Apollo Temple, being considered as the center Earth. In this type of abdominal defect we will have abdominal content like intestines or liver going outside the body, but in this case all this content is COVERED BY A SAC. Remember that in omphalocele further studies are needed in order to find out if its related with a genetic syndrome.

At last we have gastroschisis, again this word has Greek origin which means division, so again is a problem in the abdominal wall where abdominal content will be going out of the body, but in this case the main difference is the LACK OF SAC, so what does it mean? yes, all the content will be expose to amniotic fluid increasing the risk of adhesions, atresia and strictures with this increasing the need of resecting a section of the intestine (also leading to other problem: short bowel syndrome)

Treatment: for both omphalocele and gastroschisis will be surgery, but in this case the age of surgery will be determined by the size of the defect. If its a small defect can go straight to surgery, but in the other hand if its a big one, the option is create a silo over it, covering the lesion and returning it gradually to the abdominal cavity, why gradually? Imagine trying to put a melon inside an orange, hard right? well the same happens when you try to put a large lesion back to abdominal cavity, in this case will increase the risk of death of the patient because of respiratory failure (huge lesion make hard to breath!)

See you in the next topic,

Carlos Albrecht

Welcome to Team USMLE

Welcome to this fantastic journey, the USMLE road to achieve the ECFMG certification. In this blog we will try to post mnemonics, reviews, videos and links that will make this road an easy one.

 

 

teamUSMLE website and its owners and administrators (referred to as “we”) are not affiliated with USMLE® or it’s regulators such as the NBME® or the ECFMG®