Mulibrey nanism (MUL) is an autosomal recessive disease caused by mutations in 
the TRIM37 gene encoding the peroxisomal TRIM37 protein of unknown function. In 
this work, we analysed the clinical characteristics of 85 Finnish patients with 
MUL, most of whom were homozygous for the Finn major mutation of TRIM37. The 
patients' hospital records from birth to the time of the diagnosis at age 
0.02-52 years (median 2.1 years) were retrospectively analysed. All except four 
of the patients (95%) had a prenatal onset growth failure without postnatal 
catch up growth. The mean length standard deviation score (SDS) was -3.1 and 
-4.0 at birth and at diagnosis, respectively. In infancy, feeding difficulties, 
and respiratory tract infections were the most common problems. Congestive heart 
failure and pericardial constriction were diagnosed during infancy in 12% and 6% 
of the patients, respectively. At the time of the diagnosis, characteristic 
craniofacial features of scaphocephaly, facial triangularity, high and broad 
forehead, and low nasal bridge were evident in over 90% of the patients. In 
addition, practically all patients were gracile and had thin extremities. Other 
findings included a peculiar high-pitched voice (96%), yellowish dots in ocular 
fundi (79%), cutaneous naevi flammei (65%), hepatomegaly (45%), and fibrous 
dysplasia of long bones (25%). Mild muscular hypotonicity (68%) was the only 
neurological abnormality. The clinical features of the Finnish patients with MUL 
formed a distinct entity. The most consistent findings were growth failure and 
characteristic craniofacial features. However, organ manifestations varied 
considerably in early childhood. Based on these findings, we propose new 
diagnostic criteria for MUL.