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BACKGROUND We present the first Norwegian patients with spinal muscular atrophy with respiratory distress type 1 (SMARD1) with mutations in the immunoglobulin μ-binding protein 2 gene (IGHMBP2). The correct diagnosis was made more than a decade after the death of the first patient. CASE PRESENTATION Three siblings, one girl and two boys had no obvious clinical symptoms at birth. They all developed progressive respiratory failure from the age of four to six weeks, with paralysis and eventration of the diaphragm. The girl became ventilator dependent at the age of three months and died at the age of 14 months. Neurophysiological tests showed a typical findings with motor and sensory neuropathy. Autopsy showed a thin atrophic diaphragm, denervation atrophy in many muscle groups and loss of motor neurons in the anterior horns. She was diagnosed with a variant of Werdnig Hoffmann's disease. Her two brothers died nine and seven weeks old, without ventilator treatment. Autopsy of the younger boy showed similar findings as in the girl. Several years after the death of all three children the diagnosis was found to be SMARD1, as two «missense» mutations in the IGHMBP2 gene on chromosome 11q13.2-q13.4 were found in the girl. The mutation 1478C/T in exon 10 was known already, but the mutation 1263C/A in exon 9 has not been previously described. INTERPRETATION Children with respiratory failure and reduced diaphragm function during the first months of life should be examined for mutations in the IGHMBP2 gene. This report demonstrates the importance of saving biological material for further genetic tests in patients with an unclear diagnosis.