Bloom syndrome

Definition

Bloom syndrome is a rare autosomal recessive chromosomal instability disorder. Its hallmarks are prenatal and postnatal growth deficiency, photosensitive skin changes, immunodeficiency, insulin resistance and a greatly increased risk of early-onset and multiple cancers. It was described in 1954 by the dermatologist David Bloom.

Aetiopathogenesis

It is caused by loss-of-function mutations in the BLM gene (15q26.1), which encodes a RecQ helicase. Absence of the BLM protein leads to chromosomal instability, excessive homologous recombination and a greatly increased number of sister chromatid exchanges. A founder mutation (blmAsh) is carried by about 1 in 100 people of Eastern European Jewish (Ashkenazi) ancestry.

Clinical features

• Short stature from birth; narrow face with a prominent nose owing to little subcutaneous fat, long limbs.
• Telangiectatic erythema of the face, mainly over the bridge of the nose and adjacent cheeks (butterfly distribution), often aggravated by sun; cheilitis with crusting or bleeding; poikiloderma may occur.
• Frequent infections of the ears, airways and gastrointestinal tract; IgA and IgM are reduced.
• Cancers arise unusually early and often multiply, including lymphoma, acute myeloid leukaemia and tumours of the gastrointestinal tract, skin and urogenital tract.
• Reduced fertility in women.

Diagnosis

• Clinical suspicion with short stature and photosensitive facial erythema.
• Cytogenetics: greatly increased sister chromatid exchanges (pathognomonic).
• Molecular genetic detection of mutations in the BLM gene.
• Distinction from Rothmund-Thomson syndrome, erythropoietic protoporphyria and Cockayne syndrome, among others.

Differential diagnoses

• Lupus erythematosus
• Rosacea
• Dermatomyositis
• Xeroderma pigmentosum (XP)
• Ataxia-telangiectasia (Louis-Bar syndrome)
• Seborrhoeic dermatitis
• Atopic dermatitis (atopic eczema)

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References (selection)

1. DermNet: Bloom syndrome
2. PubMed: Bloom's Syndrome: Clinical Spectrum, Molecular Pathogenesis, and Cancer Predisposition (PMID 28232778)
3. PubMed: Bloom syndrome (Int J Dermatol 2014, PMID 24602044)

Cross-references