A Case of Bloom Syndrome With Uncommon Clinical Manifestations Confirmed on Genetic Testing

Comment

Patients with Bloom syndrome have a characteristic clinical appearance that typically includes photosensitivity, telangiectatic facial erythema, and growth deficiency. Telangiectatic erythema of the face develops during infancy or early childhood as red macules or plaques and may simulate lupus erythematosus. The lesions are described as a butterfly rash affecting the bridge of the nose and cheeks but also may involve the margins of the eyelids, forehead, ears, and sometimes the dorsa of the hands and forearms. Moderate and proportionate growth deficiencies develop both in utero and postnatally. Patients with Bloom syndrome characteristically have narrow, slender, distinct facial features with micrognathism and a relatively prominent nose. They usually may have mild microcephaly, meaning the head is longer and narrower than normal.^2,7-10

German and Takebe¹¹ reported 14 Japanese patients with Bloom syndrome. The phenotype differs somewhat from most cases recognized elsewhere in that dolichocephaly was a less constant feature, the facial skin was less prominent, and life-threatening infections were less common. Our patient had typical telangiectatic facial erythema without microcephaly, dolichocephaly, or any infections. She also had some uncommon manifestations such as alopecia areata, eyebrow hair loss, flat nose, reticular pigmentation, and short sharpened distal phalanges with fingernails that were wider than they were long. Although she had no recurrent infections and laboratory tests were within reference range, the alopecia areata and eyebrow hair loss may be associated with an abnormal immune response. The reasons for the short sharpened distal phalanges and the fingernail findings are unclear. The presence of reticular pigmentation also is unclear but may be associated with photosensitivity. Since the BLM gene was discovered to be the disease-causing gene of Bloom syndrome in 1995,^4,5 approximately 70 mutations were reported. The BLM gene encodes for the Bloom syndrome protein, a DNA helicase of the highly conserved RecQ subfamily of helicases, a group of nuclear proteins important in the maintenance of genomic stability.¹²

Mutation analysis of the BLM gene in our patient showed changes in 2 heterozygous nucleotide sites, including c.2603C>T in exon 13 and c.3961G>A in exon 21 of the BLM gene, which altered proline residue with leucine residue at 868 and valine residue with isoleucine residue at 1321, respectively. According to GenBank,^13,14 c.2603C>T and c.3961G>A are single nucleotide polymorphisms of the BLM gene. The genotypic distribution of International HapMap Project¹⁵ showed that C=602/602 and T=0/602 on c.2603 in 301 unrelated Chinese patients and G=585/602 and A=17/602 on c.3961 in 301 unrelated Chinese patients. Because of the low prevalence of genotypes c.2603T and c.3961A in China, the relationship between clinical features and c.2603C>T and c.3961G>A of the BLM gene in our patient requires further study.

In conclusion, we report a patient with Bloom syndrome with uncommon clinical manifestations. Our findings indicate that c.2603C>T and c.3961G>A of the BLM gene may be the pathogenic nature for Bloom syndrome in China.

Acknowledgments

The authors would like to thank the patient and her family for their participation in the study. The authors also thank Li Qi, BA, Beijing, China, for his contribution to the review of the data in the literature.