Easy yet so easily missedBMJ 2005; 330 doi: https://doi.org/10.1136/bmj.330.7499.1070-a (Published 05 May 2005) Cite this as: BMJ 2005;330:1070
- 1 Northern General Hospital, Sheffield, S5 7AU,
- 2 Rotherham District General Hospital, Rotherham, S60 2UD
- Correspondence to: A K Siota
It has been an interesting few weeks. So many doctors from all over the world have responded to Miss Webb's case.1 Numerous differential diagnoses were suggested, including Eisenmenger's syndrome, obstructive sleep apnoea, chest infection, drug overdose, heart failure, pulmonary embolism, myasthenia gravis, Guillan-Barré syndrome, atlanto-axial subluxation, Addison's disease, hypoparathyroidism, glomerulonephritis, sepsis with immune deficiency, atrial septal defect, and adult respiratory distress syndrome. Some readers questioned the diagnosis of Down's syndrome and some felt that we had deliberately withheld relevant information to make the case more interesting (definitely, not true).
Nevertheless, many respondents got the diagnosis of hypothyroidism, even from just the first part of the case report. (It was interesting that some of the readers thought about an endocrine cause because one of the authors is an endocrinologist). One of the respondents even suggested the full diagnosis of pericardial effusion and hypothyroidism. We, however, missed the diagnosis on initial presentation, probably because of our lack of awareness of an association between Down's syndrome and hypothyroidism.
Problems of diagnosis
Children with Down's syndrome usually have routine screening for hypothyroidism. We do not know why Miss Webb was not screened. You could argue that the presence of menorrhagia in itself would usually trigger most doctors to order thyroid function tests. Again, this was not done preoperatively. When Miss Webb became very unwell postoperatively, she did not have features like bradycardia, hypothermia, and low voltage QRS complexes on her electrocardiogram, and we did not suspect hypothyroidism. The delayed diagnosis led to a lot of misery for Miss Webb.
Patients with Down's syndrome are likely to have a variety of illnesses including thyroid disease, diabetes mellitus, congenital heart defects, menorrhagia, depression, obsessive compulsive disorder, hearing loss, atlanto-axial subluxation, and Alzheimer's disease. Hypothyroidism is quite common, and in one study 16% of patients with Down's syndrome had evidence of either compensated or uncompensated hypothyroidism.2 History and clinical examination may not give rise to suspicion of hypothyroidism in such patients because many of the features of hypothyroidism, such as slow growth, excessive weight gain, hypotonia, impaired mental status and dry skin, are also classic features of Down's syndrome.3
Miss Webb presented with a one year history of lethargy and menorrhagia caused by hypothyroidism. She had surgery for menorrhagia and umbilical hernia, both of which are recognised features of hypothyroidism. Slow recovery and type 2 respiratory failure after general anaesthesia are also features of hypothyroidism. Hypothyroidism affects the neuromuscular system by causing weakness of the diaphragm and other respiratory muscles. Diaphragmatic dysfunction causes a restrictive respiratory pattern that may contribute to hypoxia and hypercapnia.4 Hypothyroidism also causes diminished central response to hypoxia and hypercapnia, resulting in respiratory acidosis.4 Pericardial effusion is a common complication of hypothyroidism. The incidence in adults with untreated hypothyroidism ranges from 30% to 80% as detected by echocardiography.5
Unfortunately, our patient was not diagnosed until she became very unwell with clinically important pericardial and pleural effusions. Because of the high prevalence of hypothyroidism and the possibility of it being missed, we recommend that all patients with Down's syndrome should be tested for hypothyroidism at regular intervals and before any surgical procedure requiring general anaesthesia.
Conflict of interest None declared.