Thursday, 17 September 2009

History O'History - The Wonderful World of Dermatology

Dear Bloggers

I am back with a nice dermatological short case. As usual this patient's details have been anonymised to maintain confidentiality.

This 40 year old officer worker was admitted with an uncomplicated community acquired pneumonia. Nothing unusual about that you might think. However, the admitting doctor noticed the unusual skin rash on the patient's legs (only one shown here!). The patient had noticed this just recently and was unaware of the cause.

The patient was diagnosed with iron deficiency anaemia (IDA) several years ago of unknown aetiology. She was also known to have atopic eczema.
The doctor thought the rash was livedo reticularis and was rightly concerned that the patient might have an underlying connective tissue disease e.g. SLE (resulting in immune suppression) or perhaps an unusual hyperviscosity syndrome.

Her admission blood tests revealed an Hb of 5.9 and MCV 72. Iron and ferritin were low and TIBC was high. Blood smear confirmed the diagnosis of IDA. The cause of iron deficiency was unknown at the time of admission and the doctors were planning on doing a full 'work-up' to elucidate the cause.

When reviewed by a senior doctor, the rash did not look entirely typical for livedo reticularis which has a more telangiectatic appearance. This aside, there were flexural areas with lichenification consistent with atopic eczema.

Despite querying the patient, she could not identify the cause of the new rash. Nevertheless, the senior doctor asked a focused question below:

"Have you been putting anything hot on your legs recently e.g. hot water bottles, or sitting near a heater?"

"Yes. My office has been really cold. I have been sitting very close with my legs to my electric heater"

From this information alone the diagnosis, far from being livedo reticularis, was instead the famous and little remembered
erythema ab igne or otherwise known as erythema calorica. This is a reticulated skin reaction due to repeated heat exposure and can appear very similar to livedo reticularis. Livedo is usually more symmetrical and telangiectatic rather than erythema ab igne which is pigmented and forms dependent upon the extent and location of exposure to heat.

It is typically seen in the elderly (usually women) who sit too close to the open home fire / electric heater with their lower limbs exposed, or with hot water bottles placed on their limbs, abdomen or back. With central heating having become the norm in the UK, this condition is now rarely seen. Other people affected can be bakers or those that carry hot coals. It has also been cited as a useful marker in patients with chronic pancreatitis as the warmth helps the abdominal pain !

Please see some examples below:
Please note the differences in the presentation between darker and lighter skinned persons. Nevertheless, the 'sun burst' pattern appears to be the persistent characteristic finding here.
In such patients, hypothyroidism should be ruled out. Moreover, in view that this patient presented in late summer when the outside daytime temperature was over 27 degrees Celsius, one has to wonder if the chronic anaemia had something to do with the feeling of coldness in her legs! Remember that cold hands and feet are a symptom of anaemia!

Sometimes such interesting problems arise and using your observational skills, the right questions can be asked to build up the day-to-day life of the patient. Such problems might then point to an overall cause. Remember that patients do not know what you want to hear. You have to ask the right questions to get the answers. No 'pan-man' CT scan will give the answer here. Simple communication with the patient and using 'Sherlock Holme' skills of deduction can win the day.

In this case, further history revealed that the patient was eating just one meal a day without red meat or a good source of iron. She consumed a high amount of carbohydrate e.g. bread. Despite the high possibility of nutritional deficiency from decreased intake (and Fe loss in a regularly menstruating woman) being the likely cause of iron deficiency anaemia in this case, GI loss should be excluded in addition to causes of malabsorption e.g. celiac disease.

Diagnoses In This Case:

1) Uncomplicated community acquired pneumonia
2) Erythema ab igne

3) Chronic iron deficiency anaemia - Common things are common - likely from poor nutritional intake and menstruation.
4) Atopic eczema

For the investigation and treatment of Fe-deficiency anaemia, please see any standard EBM textbook. For a good dermatology text, I would recommend Rook's Textbook of Dermatology.