Sniffing out a hidden cause of breathlessness.

A 78-year-old man presented with severe exertional dyspnoea. He suffered from mild chronic obstructive pulmonary disease, congestive cardiac failure and seropositive myasthaenia gravis. Clinical examination of his chest and heart were unremarkable but he had speech dyspnoea and was unable to count to 20 in a single breath. Consecutive sniff nasal inspiratory measurements (SNIP) fell from 55 to 33 cm H2O and forced vital capacity (FVC) fell from 3.4 to 2.4 L. A diagnosis of myasthenic crisis was carried out and treatment with non-invasive ventilation, intravenous immunoglobulis and high-dose oral prednisolone was initiated. The patient responded well and was discharged following a short period of rehabilitation. A high index of suspicion and a careful clinical examination with the help of two simple bedside tests, FVC and SNIP, allowed correct and timely treatment of his condition.