Q. I have a new patient, a 23-year-old woman, who has significant clubbing of her fingernails (chronic swelling, or deformity of the nail bed) on both hands. She was referred from a renal specialist, who suspected she had an eating disorder because of her low weight. Can you comment on this? (A.C., Phoenix)
A. The renal specialist was likely on the right track.Two reports have linked laxative abuse and clubbing of the fingernails. In the first report, Dr. Olivia A. Charlton and colleagues at Royal North Shore Hospital, Sydney, Australia, described a 36-year-old woman with numerous gastrointestinal problems, a body mass index (BMI) of 16.8 kg/m2, and an intake of at least 15 senna- or docusate (Coloxyl™) tablets a day (J Eat Disord. doi.org/1186/s40337-019-0236-4; e-pub before print). The second study, by Saidfudin Rashique, MB, and co-workers at the University of Alberta, linked clubbing to excess ingestion of herbal tea (Can Resp J. 1996; 3:269).
The common dominator in the two reports was continuous excess ingestion of senna-containing laxatives; another was that the laxative abuse developed in an attempt to control weight. All of the few cases reported since the first study in 1975 (Silk et al.) involved young, underweight women. The mechanism that causes clubbing is still uncertain, and Dr. Charlton and colleagues stress that the diagnosis should only be made after first ruling out pulmonary, cardiac, gastrointestinal, and cancer-related causes for the clubbing. In Dr. Rashique’s report, the patient was 47 years old and had been admitted to the hospital for investigation of abdominal pain and finger clubbing. She had a decade-long history of constant pain in all areas of her abdomen that was not relieved by changing posture, therapeutic agents, or dietary manipulation. She had undergone extensive testing that yielded no clues. When seen, she weighed 48 kg (105 lb). When the clinicians re-visited the patient’s history, the patient reported having used an herbal tea preparation as a laxative for more than 30 years; she thought this was a healthy, non-pharmaceutical way to have normal bowel movements. The senna compound (Bekunis®) contained 2.5% Tinvelly Senna by weight.
It is still not known how senna abuse can cause finger clubbing, and very few cases have been reported in the literature. One theory (Dickinson, Eur J Clin Invet.1993;23:330) is that the local tissue growth results from deposits of megakeratocytes and platelet clumps in the fingertips. It seems possible that it was a direct effect of senna but also possible that chronic fluid and electrolyte changes from laxative use played a role.