A teenage girl had the rare combined phenotype of xeroderma pigmentosum and trichothiodystrophy, resulting from mutations in the XPD (ERCC2) gene involved in nucleotide excision repair (NER). After treatment with antibiotics, including metronidazole for recurrent infections, she showed signs of acute and severe hepatotoxicity, which gradually resolved after withdrawal of the treatment. Cultured skin fibroblasts from the patient revealed cellular sensitivity to killing by metronidazole compared with cells from a range of other donors. This reveals that the metronidazole sensitivity was an intrinsic property of her cells. It is well recognized that patients with Cockayne syndrome, another NER disorder, are at high risk of metronidazole-induced hepatotoxicity, but this had not been reported in individuals with other NER disorders. We would urge extreme caution in the use of metronidazole in the management of individuals with the xeroderma pigmentosum and trichothiodystrophy overlap or trichothiodystrophy phenotypes.

Xeroderma pigmentosum (XP) and trichothiodystrophy overlap syndrome is a rare autosomal recessive disease in which mutations in genes involved in nucleotide excision repair (NER) and transcription pathway result in patients with features of both XP and trichothiodystrophy.13  XP is typically characterized by severe sensitivity of the skin to sunlight and by a >1000-fold increased risk of skin cancers due to the failure to repair DNA damage induced by exposure to the UV component of sunlight. Some individuals also develop progressive neurologic deterioration.4,5  In contrast, individuals with trichothiodystrophy have brittle, sulfur-deficient hair and multisystem abnormalities, including intellectual impairment, growth retardation, and vulnerability to infection.6,7  Approximately 50% of patients with trichothiodystrophy show unusual sunburn sensitivity without developing skin cancer. Remarkably, most of the sun-sensitive trichothiodystrophy patients harbor germ-line mutations in the XPD (ERCC2) gene despite the differences in phenotype of the 2 disorders.2,6  In the few cases described in the literature of patients with XP and trichothiodystrophy overlap syndrome,1,2  the affected individuals are compound heterozygotes for mutations in the XPD (ERCC2) gene. In 3 of the 4 cases described, 1 allele contains a mutation found frequently in patients with trichothiodystrophy, whereas the mutation in the second allele has not been reported in other patients but is presumably responsible for the features of XP.

Metronidazole is a synthetic nitroimidazole derivative antibiotic commonly used in the treatment of infections caused by anaerobic bacteria and protozoa. It is relatively nontoxic to aerobic host cells, but hepatotoxicity after its use, although rare, has been described in patients without a genetic syndrome.8  Metronidazole’s mechanism of antibacterial action is based on the reduction of its nitro group leading to the production of short-lived cytotoxic intermediates, which eventually decompose into nontoxic end products. The toxicity of the intermediates is due to their interaction with DNA and possibly with other macromolecules. Metabolic pathways of low redox potential that are linked to ferredoxin or flavodoxin-like electron transport components reduce nitroimidazoles with great efficacy. Such pathways are characteristic of susceptible anaerobic protozoa and bacteria but are absent in nonsusceptible aerobic cells of the human host.9 

Metronidazole-induced hepatotoxicity has been described in patients with Cockayne syndrome (CS) (another autosomal recessive disorder associated with defects in NER) by Wilson et al10  with some fatalities. Postmortem examination in one case identified extensive hepatic necrosis with variable loss of hepatocytes throughout the liver and lobular fibrosis between remaining hepatocytes. Metronidazole and its related compounds are now accepted as contraindicated for use in individuals with CS. Toxicity has not previously been reported in individuals with other NER disorders. Here, we report a case of metronidazole-induced hepatotoxicity in an individual with XP and trichothiodystrophy overlap and present our in vitro findings, which confirm the sensitivity of her fibroblasts to this antibiotic.

The patient is a girl who was born at 38 weeks’ gestation with a birth weight of 2.6 kg (second percentile) and length of 47 cm (fifth percentile). As typical of trichothiodystrophy,11  pregnancy was complicated by maternal preeclampsia starting at 20 weeks’ gestation, but delivery was uneventful. Retrospectively, the index sign of her condition was extreme sun sensitivity when she was 10 days old. As an infant, she was photophobic and intermittently had erythema and watery eyes. From the age of 3 years, she had recurrent allergic rhinitis and upper respiratory infections. These subsided after an adenoidectomy and she had not had further problems with infections. She received speech therapy and occupational therapy through school.

At her initial presentation to clinical services at the National Institutes of Health in the United States at the age of 5 years, her height was in the 90th percentile, her weight was in the 50th percentile, and her head circumference was in the 17th percentile for occipitofrontal circumference. She had a few lightly pigmented lentigines on her face and lips. Neuropsychological evaluation revealed a full-scale IQ of 73 with significant difference between her average verbal-auditory abilities and her less well-developed motor speed and attention to visual detail. MRI of her brain revealed hypomyelination of the white matter. Radiographs of bones revealed mild osteopenia of feet, minimal osteopenia of hands, and bilateral coxa valga of hips. Audiograms were normal. She had long scalp hair that was brown and coarse. Examination of her hair sample under polarized light revealed indeterminate tiger-tail patterning and areas of hair shaft abnormalities, including trichorrhexis nodosa and ribboning (Fig 1). Amino acid analysis identified a pattern intermediate between normal and trichothiodystrophy that is consistent with the XP and trichothiodystrophy phenotype.12 

FIGURE 1

Trichothiodystrophy hair features. Hair shafts under polarizing microscopy in panel A reveal tiger-tailed banding (black arrow) and in panel B reveal trichorrhexis nodosa-like fracture (hatched arrow).

FIGURE 1

Trichothiodystrophy hair features. Hair shafts under polarizing microscopy in panel A reveal tiger-tailed banding (black arrow) and in panel B reveal trichorrhexis nodosa-like fracture (hatched arrow).

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The patient received a diagnosis at the National Institutes of Health in the United States at the age of 5 years with combined features of XP and trichothiodystrophy. A fibroblast culture was established and designated XPTTD392BE. Molecular analysis revealed compound heterozygous mutations in the XPD (ERCC2) gene: c.335G>A (p.Arg112His); c.1996C>T (p.Arg666Trp). The former mutation has been reported in several trichothiodystrophy or XP and trichothiodystrophy patients, both homozygous and compound heterozygous,13,14  whereas 2 patients with the combined XP and CS phenotype were compound heterozygous for c.1996C>T (p.Arg666Trp).15  NER, as measured by unscheduled DNA synthesis, was 20% to 30% of normal, typical of other XP and trichothiodystrophy patients with mutation in the XPD gene.

At the age of 16 years (Fig 2), our patient presented acutely to a hospital in the United Kingdom with jaundice, dizziness, and abdominal pain after a 1-week history of vomiting. In the preceding weeks, she had been treated by her general practitioner for a persistent lower respiratory infection characterized by a persistent cough with courses of antibiotics. This included 2 weeks of amoxicillin (at a dose of 500 mg 3 times a day), to which metronidazole (at a dose of 400 mg 3 times a day) was added to cover for the possibility of aspiration pneumonia because she was showing little improvement. Her symptoms started on the fifth day of a 5-day course of metronidazole. Dosage for both was appropriate per the British National Formulary for Children for her age; doses did not require adjustment because her weight at the time of 57 kg was in the 50th percentile. On initial examination in the hospital, she had signs of acute liver disease, primarily jaundiced sclera, liver flap sign, and abdominal tenderness over the right upper quadrant.

FIGURE 2

The patient with XP and trichothiodystrophy overlap syndrome at the age of 16. She has long but coarse hair, relative enophthalmos, severe retrognathia, and lightly pigmented lentigines on the face.

FIGURE 2

The patient with XP and trichothiodystrophy overlap syndrome at the age of 16. She has long but coarse hair, relative enophthalmos, severe retrognathia, and lightly pigmented lentigines on the face.

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Initial blood investigations revealed signs of dehydration and acute hepatitis, such as hyperbilirubinemia, raised transaminases (alanine aminotransferase ALT 2292 IU/L [normal range: 4–40 IU/L]), deranged coagulation screen, low albumin, raised fibrinogen, and dramatic increase in ferritin. Further blood investigations to determine the cause of the hepatitis profile were normal, including hepatitis A, B and C, caeruloplasmin, autoantibody screen, copper, cytomegalovirus, Epstein-Barr virus, and adenovirus. α-Fetoprotein was raised to 2247 kU/L, but further imaging of the liver with MRI excluded cirrhosis and hepatocellular carcinoma.

Over the course of a few days, with supportive treatment, including intravenous fluids, vitamin K, ursodeoxycholic acid, Dalivit, and vitamin E, the clinical symptoms of vomiting and diarrhea abated and the signs of liver injury, including her coagulopathy, resolved. She was discharged from the hospital after 10 days and resolution of her symptoms. Blood tests were monitored weekly. α-Fetoprotein declined to normal over a period of weeks, suggesting that its increase was probably entirely related to the liver injury. Approximately 16 weeks later, liver function test was also almost normal. Periodic testing of her liver function has since revealed that they become deranged with intercurrent illness but with no other associated signs of liver failure, such as low albumin or deranged clotting. The abnormal liver function test indices have usually self-resolved.

To test whether the metronidazole sensitivity seen in the patient was an intrinsic property of her cells, the sensitivity of her fibroblasts was compared with that of cells from other patients with CS, XP, and trichothiodystrophy. Primary fibroblasts used in these experiments were from 2 normal donors, 1BR and 48BR; CS donors, CS16BR and CS35LO; the patient, XPTTD392BE; a trichothiodystrophy donor, TTD1BEL, compound heterozygous for mutations p.[Arg722Trp]; [Arg616Pro] in the XPD protein16 ; and an XP donor XP135LO, homozygous for p.[Arg683Trp].14  Cells were treated for 24 hours with 5 mg/mL metronidazole. The cells were trypsinized and plated onto feeder layers, which had been irradiated with 35 Gy γ-irradiation. Colonies were counted after 21 days. Colony-forming ability of treated cells was compared with that of the the untreated cells.17 

Results in Fig 3 reveal that, as reported, cells from a patient with CS were somewhat more sensitive than 2 normal cell lines to 5 mg/mL metronidazole, but cells from our patient were much more sensitive. To check whether this hypersensitivity was also seen in other trichothiodystrophy or XP cell lines, we also tested a further trichothiodystrophy and an XP-D cell line. Their sensitivity to metronidazole was comparable to that of the normal controls.

FIGURE 3

The survival of fibroblasts treated with 5 mg/mL Metronidazole for 24 h was compared with that of untreated cells. Results reveal means + SEMs for 6 experiments (1BR and XPTTD392BE), 4 experiments (48BR, TTD1BEL, and XP135LO) and combined data of 1 experiment with each of CS16BR and CS35LO.

FIGURE 3

The survival of fibroblasts treated with 5 mg/mL Metronidazole for 24 h was compared with that of untreated cells. Results reveal means + SEMs for 6 experiments (1BR and XPTTD392BE), 4 experiments (48BR, TTD1BEL, and XP135LO) and combined data of 1 experiment with each of CS16BR and CS35LO.

Close modal

Our results reveal that the sensitivity of our patient to the toxic effects of metronidazole is an intrinsic property of her cells. This could explain her clinically apparent reaction. We did not find corresponding sensitivity in 1 other trichothiodystrophy or XP cell line with mutations in the XPD gene, so we cannot at this point conclude whether the sensitivity is related to the XPD mutation and may therefore be found in other trichothiodystrophy patients. Another of our trichothiodystrophy patients, TTD383BE with mutations in the XPD (ERCC2) gene, died of liver failure at age 7 years. She was diagnosed with Clostridioides difficile infection. We have not been able to determine if she was treated with metronidazole, a drug often used for therapy of C. difficile infections. However, there are many reports that reveal marked heterogeneity in clinical symptoms in XP and trichothiodystrophy patients with germ line mutations in the XPD gene. The sensitivity to metronidazole in our patient may be due to the combination of mutations identified on both XPD alleles.18  Cells from a variety of other trichothiodystrophy patients with different XPD gene mutations would need to be tested to reach a definitive conclusion on this point. Patients with CS with NER defects who received metronidazole showed serious adverse effects, such as hepatotoxicity.10 

Hepatotoxicity from metronidazole has rarely been reported in the general population, despite widespread use.19  There have not been any previous reports of metronidazole-induced hepatotoxicity in an individual with the XP and trichothiodystrophy overlap syndrome. Further work is therefore needed to confirm this finding, but, in the meantime, we would urge extreme caution in the use of this antibiotic in the management of individuals with the XP and trichothiodystrophy overlap or trichothiodystrophy phenotypes.

We are grateful to the patient and her family for kindly consenting to the publication of this report. We are indebted to Dr Ken Kraemer, in whose laboratory at the National Cancer Institute the initial diagnosis and molecular characterization were conducted, and to Dr Paula Beattie, a dermatologist, who looked after the patient locally. Both of these colleagues should have been coauthors, but in view of the constraints on numbers of authors imposed by this journal, they generously accepted instead this acknowledgment of their roles. We thank all the specialist members of the UK multidisciplinary XP clinical team for their clinical evaluation of the patient. All the clinical and cellular assessments in the United Kingdom were conducted by the National Xeroderma Pigmentosum Service, which is funded by the National Health Service England Highly Specialised Services.

FUNDING: No external funding.

Drs DiGiovanna and Khan and Ms Tamura initially diagnosed and analyzed the patient in the United States, collected data, conducted the initial analyses identifying the pathogenic mutations, and reviewed and revised the manuscript; Drs Cordeiro, Adesoji, and Fassihi, and Prof Lehmann conceptualized and designed the study, drafted the initial manuscript, and reviewed and revised the manuscript; Ms Fawcett and Prof Lehmann designed the data collection instruments, conducted the metronidazole sensitivity cellular experiments, coordinated data collection, and critically reviewed the manuscript; and all authors contributed to writing the manuscript and approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

     
  • CS

    Cockayne syndrome

  •  
  • NER

    nucleotide excision repair

  •  
  • XP

    xeroderma pigmentosum

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Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.