Introduction: Opportunistic infections are a recognised complication of severe hypercortisolism. We report a case of Pneumocystis Pneumonia (PCP for formerly named Pneumocystis carinii pneumonia) in patient with ectopic Cushing's syndrome (CS) caused by a metastatic neuroendocrine carcinoma of the lung.
Case history: A 61-year old male attended the Acute Medical Unit for investigation and treatment of severe and recurrent hypokalaemia. His random cortisol at presentation was 1404 nmol/L, ACTH 250 ng/L(normal <50) and 24-h urine free cortisol of 6363 nmol/24 h (upper limit of normal 270). Other cushingoid features included hypertension, easy bruising and central fat distribution. Further endocrine investigation suggested ACTH-dependent hypercortisolism of non-pituitary origin. Whole body CT demonstrated a left upper lobe lung nodule with multiple liver metastases. Liver biopsy and immune-histochemistry confirmed large cell neuroendocrine carcinoma. Following treatment with metyrapone and ketoconazole, the hypokalaemia resolved and hyper-cortisolaemia improved. One week after initiation of treatment the patient developed a cough, temperature and shortness of breath. CT Pulmonary Angiogram showed bilateral upper lobe dense consolidation. Broncho-alveolar lavage revealed Pneumocystis jirovecii (formerly PCP) and the patient was treated with trimethoprim and sulfamethoxazole.
Discussion: Similar to our case, PCP has been diagnosed after initiation of cortisol-lowering therapy in the majority of the reported cases in patients with CS. This suggests that immune reconstitution is an important component or even a prerequisite for development of clinically overt PCP in this population. There seems to be a relationship between the degree of hypercortisolism and the susceptibility to opportunistic infections. Our case highlights the fact that patients with severe hypercortisolaemia, more commonly seen in ectopic ACTH syndrome, may be at particular risk of PCP infection following treatment with cortisol-lowering agents. Prophylaxis against pneumocystis jirovecii should be considered before starting cortisol-lowering therapy in order to minimise the risk of PCP.