Pistachio-green stools and anaemia in infancy: early signs of cystic fibrosis?

Abstract

Stool characteristics may vary in healthy infants and are influenced by the type of feeding. Whereas almost all breastfed infants have yellow loose stools, formula-fed infants’ stools may be green, brown, or yellow. In cystic fibrosis (CF), meconium ileus or other meconium abnormalities may be the earliest manifestations, while later in infancy the gross stool characteristics are generally described as frequent, voluminous, loose, greasy, and foul-smelling. I report two anaemic infants with striking pistachio-green stools who were later diagnosed with CF. A 4-month-old breastfed girl was referred for anaemia and suspected occult intestinal bleeding. She was born after 40 weeks of gestation with no reported complications, birth weight 3400 g. Postnatally she had stayed in London with her English father’s family where she had been investigated for anaemia and failure to gain weight. Haemoglobin was 7·1 g/dL, packed cell volume 22%, reticulocytes 4·2%, mean-cell volume and mean cell haemoglobin concentration at the lower end of normal, platelets 548 10/L, and serum iron, folate, and cobalamins were all normal. There were no signs of haemolysis. Several tests for faecal haemoglobin had been positive but she had not passed any visible blood. We recorded almost identical results 4 weeks later, and also that the serum albumin was 24 g/L and the prothrombin complex 45%. Her body weight was then 5100 g. The stools were loose, smooth, and bright pistachio-green, without any remarkable odour or greasy appearance, and occasionally positive for haemoglobin. A rectoscopy, technetium scan, and bone marrow smear were all normal. No explanation for the anaemia was found and after a blood transfusion she maintained a normal haemoglobin and started to gain weight and length. The stools remained pistachio-green until about 8 months of age. At the age of 2 years and 9 months she was readmitted for pneumonia and a chest radiograph showed peribronchial opacities indicative of CF, which was confirmed by subsequent investigations including an abnormal sweat test. An 8-week-old boy was born without complications after 37 gestational weeks with a birth weight of 2950 g. He was entirely breastfed and his mother reported that his stools invariably were green. He had had projectile vomits once or twice daily since 4 weeks of age and had therefore been sent for a barium meal (which was normal). Immediately after this he was seen by me in the casualty department and he then appeared anaemic and miserable but otherwise normal, except that his body weight was only 3710 g. His napkin (diaper) contained puree-like pistachio-green stools mixed with some of the contrast agent. No remarkable odour or greasy appearance was noticed. I admitted him for further investigations. Laboratory tests showed haemoglobin 7·5 g/dL, packed cell volume 26%, reticulocytes 9·8%, and serum albumin 14 g/L; all other blood tests were normal. One in eight stools were positive for haemoglobin. He had bacteriuria and was therefore put on co-trimoxazole and the vomiting improved. Since his haemoglobin dropped to 6·9 g/dL during the next few days he was transfused to 12·4 g/dL. Initial investigations revealed no bleeding source and a bone marrow aspirate was normal. He was readmitted 4 weeks later because his haemoglobin had dropped to 9·8 g/dL, packed cell volume to 32%, and reticulocytes to 2·8%. The serum albumin remained at 12 g/L and he had developed dorsal foot oedema. Liver enzymes were moderately raised. Investigations, including an abnormal sweat test, now confirmed the diagnosis of CF. The laboratory abnormalities improved and the oedema resolved soon after oral treatment with pancreatic enzymes had been started. His stools were more normal 1 month later. Anaemia in infants with CF may be due to protein-energy malnutrition or inadequate erythropoiesis, or both. Proteinenergy malnutrition may preferentially affect breastfed infants with CF and was present in both cases as indicated by hypoalbuminaemia and poor weight gain. The pistachio-green stools are harder to explain, but may be due to excretion of increased faecal bile acids following malabsorption of the relatively diluted and supersaturated bile (with cholesterol) that is produced in infancy. A defect in intestinal absorption of iron might contribute. If so, the association of anaemia, hypoproteinaemia, slow weight gain, with pistachio-green stools in infants with CF is plausible. Epidemiological studies are now needed.