Severe Haemolytic Anaemia Secondary To Avian Allergy
Authors: David Taylor , Keenan Russell 
Published: October 2019

Summary
We present the first case of pigeon allergy causing severe haemolytic anaemia. Serology demonstrated very high titres of antibodies to avian proteins; in excess of those seen in the majority of cases of allergic lung disease1. Observation, immunosuppressive therapy and attempts at reducing antigen exposure were ineffective in controlling the disease. The only effective measure was culling the birds which resulted in a swift remission in the patient’s illness.

Background
Avian allergic diseases are well documented including extrinsic allergic alveolitis and asthma. However, from a review of the literature, haemolytic anaemia has not yet been described.

Case Presentation
An eight year old boy presented to accident and emergency with malaise, pallor and a sore throat. Haemoglobin was 53g/L. Further clinical examination revealed splenomegaly of 3.5cm below the costal margin.

Investigations
Full blood count demonstrated marked anaemia and a reticulocytosis (Hb 53g/L, WBC 2.2 x109/L, Neuts 1.3 x109/L, Lymphs 0.6 x109/L, Platelets 186 x109/L, Reticulocytes 375 x109/L). Blood film demonstrated increased polychromasia and microspherocytes. Direct coombes test was negative.

Differential Diagnosis
The patient’s haemoglobin stabilised following a short period of time in hospital. Red blood cell transfusion and immunosuppressive therapy were not required at this stage. Despite stable haemoglobin concentrations there continued to be evidence of haemolysis throughout the first year of follow-up. This was complicated by gallstone disease which required open cholecystectomy. School attendance was adversely affected.
In view of the prolonged duration of the illness the patient was screened for congenital and acquired causes of haemolysis. No cause was found for the condition. Three years later the patient experienced decompensated haemolysis with a fall in his haemoglobin to 66g/L and symptoms of lethargy and malaise. His splenomegaly was more marked at 5.0cm. He was commenced on prednisolone (1mg/kg) which stabilised his blood count but was complicated by psychiatric disturbances. During a routine follow-up appointment the patient disclosed that he kept over 100 racing pigeons at his home. He was involved in their care on a daily basis and would regularly race the birds in competitions. Serological testing demonstrated high titres of antibodies to avian proteins (pigeon and budgie serum, feather and droppings >200x103 mg/L). These levels are in excess of those seen in the majority of cases of allergic lung disease1.

Treatment
Initial attempts to reduce exposure were ineffective. Following discussions with the family the birds were culled. There was an immediate and dramatic effect on reticulocytes and within a month it was possible to begin reducing the steroid dose. Over the following year there was a progressive rise in his haemoglobin associated with a continued fall in the reticulocytosis. Steroids were discontinued at four months. Three years following the removal of the causative agent the patient remains well and off treatment.

Discussion
Avian proteins are commonly cited as a cause for immune conditions, predominantly those affecting the respiratory system. This is the first case of avian allergic haemolytic anaemia. This case highlights the importance of consideration of unusual pathologies.

Competing interests
None

Patient consent
Not obtained.
References
1) C I Baldwin, A Todd, J E Calvert. Pigeon fanciers' lung: effects of smoking on serum and salivary antibody responses to pigeon antigens. Clin Exp Immunol. 1998 Aug;113(2):166-72.

Disclosures:
No relevant conflicts of interest to declare.