PURPLE DIAPER SYNDROME IN GERIATRICS

Abstract

To the Editor: Blue diaper syndrome is a rare metabolic disorder in infants with autosomal recessive inheritance and is characterized by bluish urine–stained diapers due to indigo and hypercalcemia with nephrocalcinosis.1 A defect in the intestinal transport of tryptophan causes this syndrome. Bacterial degradation of tryptophan in the colon leads to the presence of excessive indole and consequently to indicanuria.1 Here we report that a similar bluish-purple staining was found in the diapers of an elderly nursing home resident, which led to early recognition and treatment of an underlying severe urinary tract infection. Purple diaper syndrome may be analogous to the more familiar “purple urine bag syndrome” (PUBS)2 characterized by a purple discoloration of the urinary catheter bag and tube. This is typically seen in immobile elderly women with chronic constipation and urinary tract infection. The patient, a 90-year-old female nursing home resident, had a 3-year history of Alzheimer's disease and chronic heart failure, and she was unable to do anything without the assistance of caregivers except eat and turn in bed. Examination revealed moderate dementia, with a Mini-Mental State Examination score of 8 of 30 and frailty, as indicated by a low Functional Independence Measure score (21/126). Laboratory findings were normal, including calcium serum level. Because she had incontinence, the patient required diapers. The patient was constipated and needed habitual use of laxatives. Six months after placement, a bluish-purple urine staining was noticed on her diapers over several days, followed by lethargy and loss of appetite and mobility, although there was no fever. Urinary catheterization yielded brownish-red turbid urine with an odor of putrefaction. Urinalysis revealed a highly alkaline urine pH of 8.5 and a moderate number of leukocytes, and the urine culture grew Escherichia coli (>100, 000 colony forming units/mL). The blood leukocyte count rose to 15,200/μL and C-reactive protein was 21.7 mg/dL. It was not possible to assay urinary indican, because there is no commercial laboratory service in Japan that can perform the analysis. There are conflicting results in the literature regarding indican, which is present in the urine of healthy adults,3 whereas indicanuria has not been detected in an otherwise typical patient with PUBS.4 The bluish-purple discoloration of the diapers disappeared shortly after antibiotic treatment, which was similar to that seen in cases of PUBS.4-6 PUBS is an uncommon syndrome associated with urinary tract infections and is mainly observed in chronically catheterized and constipated women. The urinary catheter drainage changes color from light violet or blue to deep indigo or purple. Indigo blue and indirubin red are responsible for these colors.7 Similar to blue diaper syndrome,1 the origin of PUBS begins with dietary tryptophan metabolized by gut bacteria.2 Bacterial overgrowth associated with constipation produces excessive indole, which is absorbed and converted into indican (indoxyl sulfate) in the liver. Indican excreted in the urine oxidizes to insoluble indigo and indirubin after bacterial enzymatic degradation7 and exposure to air.8 Bacterial enzyme–induced urine alkalization also facilitates PUBS.5, 9 A recent case-controlled study showed no causative relationship between bacterial species and PUBS.5 By contrast, a high bacterial count is a major factor indicative of PUBS.5 Although PUBS is generally considered to be a benign clinical condition,5, 8 it has reportedly resulted in severe urinary tract infections and subsequent sepsis.4, 6 Urinary tract infections are one of the most common problems in older people, and the clinical manifestations can be atypical; thus, we suggest that purple diaper syndrome, albeit rare, is a useful clue for caregivers indicating the possibility of urinary tract infection. An insoluble bluish-purple pigment is precipitated on the pad surface after the urine is absorbed into the diaper. By contrast to PUBS, purple diaper syndrome may have escaped recognition, not only because of an unfounded attribution to food or medications, but also because of the paucity of relevant observations from geriatric health professionals. Financial Disclosure: None. Author Contributions: Atsushi Komiyama was the sole author of this letter. Sponsor's Role: None.