Registrar teaching

5 year old developed a red rash around lips after eating cherry tomatoes on several occasions.

SPT to fresh tomato - 2mm wheal.

You should advise her parents:

• She has pollen-food allergy syndrome

• She has IgE mediated food allergy to tomato

• The reactions are due to chemical irritation

• She should have a supervised food challenge

Answer explanation

Erythematous perioral reactions are common contact reactions due to chemical irritation, not immune mechanisms. Strawberries and tomatoes are common causes. The skin prick test is negative, which is further evidence against an IgE mediated allergy.
Pollen-food allergy syndrome (or oral allergy syndrome) is caused by an IgE mediated immune reaction to inhaled allergens (pollens), cross-reacting with food proteins found in raw fruits and vegetables and nuts (class II food allergy).

Pollen-food allergy can be confirmed with SPT to the fresh food (prick to prick testing) and to the pollen.

Typical symptoms of food pollen allergy syndrome include?

• Red, swollen, itchy lips

• Itchy nose + ears

• Angioedema

• Oral red patches and blisters

Answer explanation

Typical symptoms affect the lips, mouth and throat including:

• - Redness, swelling, itching of the lips, and oral mucosa

• - Itch of the nose and ears

• - Angioedema

• - Oral red patches and blisters

• - Difficulty swallowing

• - Hoarse voice

• - Tightness in the throat.

Your patient with birch pollen allergy develops an itchy mouth when she eats apple.

Is she at risk of anaphylaxis?

• Yes

• No

Answer explanation

Pollen-food allergy syndrome can rarely cause anaphylaxis

(1–2%)

Her mother asks if she can eat cooked apple?

• Yes

• No

Answer explanation

Treatment for pollen-food allergy syndrome:

• - Avoid trigger foods

• - Cooking the trigger foods before eating: this is not effective for soybeans, celery, peanuts, and other nuts

• - Accidental ingestion: rinsing mouth with water may help to reduce symptoms

• - Pollen immunotherapy

• - Subcutaneous immunotherapy to apples if relevant

• - Self-injectable adrenaline (epinephrine) should be carried if there is a history of anaphylaxis.

A 4 year old boy presents with recurrent respiratory tract infections since the age of 2 years, and concerns regarding an unsteady gait.

The following clinical signs are found on examination:

Diagnosis?

• Ataxia-telangiectasia

•  Friedreich's ataxia

• Spinocerebellar atrophy

• Metachromatic leukodystrophy

Answer explanation

Ataxia-telangiectasia is a rare inherited disorder caused by mutation in the ATM gene. Symptoms include:

• Ataxia/lack of co-ordination/unsteady gait/abnormal movement pattern

• Telangiectases on the skin and eyes

• Combined immunodeficiency resulting in recurrent respiratory infections

• A predisposition to malignancy (leukaemia and lymphoma)

Lab features include low IgA, increased alpha-fetoprotein, Increased radiation-induced chromosomal breakage in cultured cells, and mutations in the ATM gene.

Genetic testing is most likely to reveal:

• WASP gene mutation

• JAK3 mutation

  
  

• 22q11.2 deletion

• ATM gene mutation

Answer explanation

Ataxia telangiectasia is associated with mutations to the ATM gene

The WASP gene is associated with Wiskott-Aldrich syndrome (presents early infancy with bloody diarrhoea, eczema, immunodeficiency, and predisposition to cancer; lab features include thrombocytopenia with small platelets, low IgM, declining number and function of T cells)

JAK3 mutation is associated with severe combined immunodeficiency

22q11.2 deletion is associated with DiGeorge syndrome (absent/hypoplastic thymus with variable T cell immunodeficiency).

An 8 day old term baby presents with diarrhoea since day 3. She has profuse watery stools more than 10 times per day.

Birth weight was 3.0kg and she now weighs 2.55kg. She is feeding hungrily.

On exam she looks malnourished, capillary refill time is 4 seconds, and heart rate is 180 bpm.

You fluid resuscitate her and admit her to the ward nil by mouth on IV fluids. Despite being nil by mouth, her diarrhoea continues. Stool culture and PCR panel is negative. Her blood gas is normal. Her faecal sodium is 110 mmol/L (n ~ 30) and

You calculate her faecal osmolar gap to be 45 (n 50 - 100).

What type of diarrhoea does she have?

• Secretory diarrhoea

• Osmotic diarrhoea

Answer explanation

The faecal osmolar gap (FOG) helps determine if diarrhoea is caused by osmotic imbalances or other factors, like malabsorption of carbohydrates. It's calculated by subtracting twice the sum of fecal sodium and potassium concentrations from a standard stool osmolality (typically 290 mOsm/kg). A high FOG (above 125 mOsm/kg) suggests osmotic diarrhea, while a low FOG (below 50 mOsm/kg) suggests secretory diarrhea or other causes. 

The most likely diagnosis is:

• Coeliac disease

• Fructose intolerance

• Congenital chloride-losing diarrhoea 

• Congenital microvillus inclusion disease

Answer explanation

• Congenital chloride-losing diarrhoea is a rare cause of secretory diarrhoea 

• Mutations in SLC26A3 gene lead to defective chloride–bicarbonate exchange causing loss of chloride and retention of bicarbonate.

• A child with congenital chloride-losing diarrhoea would have an abnormal blood gas.

• Coeliac disease is excluded because the baby is not on gluten containing diet

• She is also not having fructose

• The diarrhoea is secretory (determined by stool electrolytes/osmolar gap, and ongoing diarrhoea despite gut rest)

• Congenital microvillus inclusion disease is an extremely rare autosomal recessive enteropathy. There is hypoplasia and/or atrophy of the villus and defective brush-border.

A female neonate has oedema of the dorsum of her hands and feet and loose skin folds at the nape of her neck. Diagnosis?

• Trisomy 21

• Idiopathic congenital lymphoedema

• Trisomy 13

• Turner syndrome

Answer explanation

• Oedema of the dorsum of hands and feet and loose skin folds at the nape of the neck are characteristic findings in Turner syndrome

• Over half of girls with Turner syndrome have a 45,X karyotype, others have a combination of monosomy X and normal cells (45, X/ 46, XX)

• In older children, a webbed neck, broad chest with wide-spaced nipples, cubitus valgus, and short stature are characteristic features.

What cardiac condition is most likely associated?

• Bicuspid aortic valve

• Supravalvular aortic stenosis

• Pericarditis

• Pulmonary stenosis

Answer explanation

• 35% of girls with Turner syndrome have cardiac abnormalities

• The common findings include bicuspid aortic valve, coarctation of the aorta, and aortic wall abnormalities

• Cardiology follow up with monitoring of the aortic dimension is required.

• Supravalvular stenosis and pulmonary stenosis are the two most common abnormalities in Williams syndrome.