Water pipe smoking as a cause of secondary erythrocytosis.

Water pipe (WP) smoking has become very popular in European countries. A 27-year-old male patient was referred to our clinic with erythrocytosis of unknown origin. His self-reported history included almost daily WP smoking since the age of 14 years. At presentation haemoglobin, haematocrit (Hct) and carboxy-haemoglobin (CO-Hb) levels were elevated to 19.7 g/dl, 54% and 15.4%, respectively. Erythrocytosis was completely reversible upon cessation of WP smoking. Upon follow-up, haemoglobin, Hct and CO-Hb levels undulated according to the intensity of WP usage. Our report shall raise awareness among physicians for WP smoking as a possible cause of secondary erythrocytosis, particularly among younger adults, and provide guidance for the clinical management.