A novel homozygous Ala529Val LMNA mutation in Turkish patients with mandibuloacral dysplasia.

CONTEXT: Mandibuloacral dysplasia (MAD) is a phenotypically heterogeneous, rare autosomal recessive disorder characterized by mandibular and clavicular hypoplasia, acroosteolysis, delayed closure of cranial sutures, joint contractures, lipodystrophy, and mottled cutaneous pigmentation. MAD patients with type A lipodystrophy with loss of sc fat from the extremities and normal or slight excess in the neck and truncal regions have been previously reported to carry a homozygous Arg527His mutation in LMNA (Lamin A/C) gene. Among those with type B pattern of lipodystrophy with generalized loss of sc fat, we recently reported a patient carrying compound heterozygous mutations in an endoprotease, zinc metalloproteinase (ZMPSTE24), gene that is involved in posttranslational processing of prelamin A to mature lamin A.

OBJECTIVE

Our objective was to carry out mutational analysis of LMNA in additional patients with MAD and type A lipodystrophy.

DESIGN AND

SETTING

We studied descriptive case reports at a referral center.

PATIENTS: Subjects were a male and a female patient with MAD who belonged to two pedigrees from Turkey.

MAIN OUTCOME MEASURES: We assessed genotype-phenotype relationships.

RESULTS

We now report that both these patients have a novel homozygous missense mutation (c.1586C-->T; c refers to cDNA reference sequence) in LMNA that replaces a well-conserved residue alanine at position 529 to valine. Intragenic single-nucleotide polymorphisms revealed a common haplotype spanning 2.5 kb around the mutated nucleotide in the parents of both the affected subjects, suggesting ancestral origin of the mutation. The female patient had no breast development despite normal menstruation, a phenotype different from that seen in women with MAD and Arg527His LMNA mutation.

CONCLUSIONS

We conclude that two homozygous missense LMNA mutations involving the arginine 527 and alanine 529 residues cause MAD with subtle variations in phenotype.