Thyroiditis

Thyroiditis syndrome also frequently come from the exam. Different condition may has various types of presentation. It can be class by pain and tenderness with no pain and tenderness as listed in below:




This is a diagram taken from NEJM. This diagram is important for quick reference on thyroiditis syndrome. You can get the original article from NEJM (n engl j med 348;26, June 26, 2003)

You also need to remember on type of thyroid malfunction caused by Amiodarone. There are 2 types, type 1 and type 2. The mechanism and treatment of both are different. Besides on causing hyperthyroidism, it also causes hypothyroidism.

Hepatitis B Virus

Hepatitis B Virus

Interpretation of serology results of Viral Hepatitis B is also one of the common topic. Below is two tables showing how to analyze the serologic data. The timing of emergence of each serologic makers or HBV DNA is important. I think you can found it in all major test books.

Serologic Markers for the Different Phases of Acute and Chronic Hepatitis B Virus InfectionInterpretation of the Hepatitis B Panel

The four possible interpretations are:

1. Recovering from acute HBV infection.
2. Test may not be sensitive enough to detect very low level of anti-HBs in serum, as patient is distantly immune
3. False positive anti-HBc.
4. Undetectable level of HBsAg present in the serum and the person is actually chronically infected.

Anion Gap

Anion Gap

Question on metabolic problem and usage of calculation of anion gap is one of the favourite questions in MRCP, either part 1 or part 2 written. Measurement of anion gap is particularly important in question pertaining to metabolic acidosis. I remember during the practice session, there is one very important note stated in the book:

IF YOU SEE CHLORIDE IN THE QUESTIONS, PLEASE CALCULATE ANION GAP.

Basics:
Before we begin further, do any one of you still remember the thing we learn in our secondary school? What is ion, anion or cation? It may seens alien now, after so many years…….
An ion is a positively or negatively charged atom or molecule, due to lost or gained of one or more valence electrons. Thus, an anion is a negatively charged ion, and a cation is a positively-charged ion.

The anion gap is calculated by equation below:
AG = (Na + K) - (Cl + HCO3) ( normal 7-17 mmol/L)

This equation can also be translated as
AG = Unmeasured anions - unmeasured cations

Based on equation 2, increased anion gap can be caused by increased unmeasured anions (some causes of metabolic acidosis) or reduction of unmeasured cations. Below is the causes of raised anion gap.

Causes of Increased Anion Gap
Renal failure
DKA
Alcoholic ketoacidosis
Lactic acidosis
Ingesion of salicylate
Methanol
Ethylene glycol
Paraldehyte
Dehydration
Exogenous anions:penicillin, carbenicillin

Among the causes of low anion gap, laboratory is the most important one that we need to entertain in our day to day practice. The causes is as below:

Causes of decreased Anion Gap
unmeasured cation:Mg2+,K+,Ca2+
Decreased unmeasured anion:Hypoalbuminemia

Some authority mentioned that if the above causes are not present, then we need to consider electrophoresis to look for multiple myeloma, as it may produce cationic paraprotein.

Finally we come to the causes of normal anion gap metabolic acidosis.

Causes of Normal Anion Gap Acidosis
RTA
Acetazolamide (Carbonic anhydrase inhibitors)
Addison's disease
Pancreatic or biliary fistula
Severe diarrhea
Ureteric diversion
Ammonium chloride ingestion