Context: Multiple endocrine neoplasia type 1 (MEN1) is a tumour syndrome of the parathyroid, endocrine pancreas and anterior pituitary caused by mutations in the MEN1 gene on 11q13.

Objective: to determine the MEN1 mutation spectrum and detection rate among Swedish patients and identify which patient categories should be tested for MEN1 mutations.

Design/ Setting/Patients: DNA sequences and referral forms from patients referred to the Department of Clinical Genetics at Karolinska University Hospital, Sweden for clinical MEN1 mutation screening were analysed. The mutation status of 371 patients (including 200 probands) was ascertained and the multiplex ligation-dependent probe amplification (MLPA) assay was evaluated for the detection of large deletions.

Main Outcome Measure(s): MEN1 genotypes.

Results: 48 of 200 index cases (24%) shared 40 different mutations (18 novel). 69% of all mutations resulted in a truncated protein. Two large deletions were detected by MLPA. 94% of all MEN1 families had a mutation in the coding region of the MEN1 gene. 6% of sporadic cases had MEN1 mutations. There was no correlation between severe disease and mutation type or location.

Conclusions: 4% of all mutations were large deletions and MLPA is now included in our standard MEN1 mutation screening. Individuals with at least one typical endocrine tumour and at least one of the following: 1) a first degree relative with a major endocrine tumour; 2) an age of onset <30 years and/or 3) multiple pancreatic tumours/parathyroid hyperplasia were most likely to harbour a mutation, thus these patients should be screened for MEN1 mutations.