Results: The homozygous deletions of exons 7 and 8 of the SMN1 gene were found in 94% and 87% of the patients. Exon 5 of the NAIP gene was deleted in 70%, but its deletion was more frequent in SMA type I (93%) as compared to type II (54%) and type III (43%). Seven patients with SMA diagnosis did not show any of the above homozygous deletions. All 230 control subjects had at least one copy of both SMN1 and NAIP genes, as expected. Conclusion: Our results demonstrate that the deletion rate (94%) of the SMN1 gene in Saudi SMA patients is similar, irrespective of types, compared with patients of other ethnic groups. We also show that the incidence of NAIP deletion is higher in the more severe SMA cases and the dual deletion of the SMN1 and NAIP genes are more common in Saudi SMA type I patients compared with patients of other ethnic groups. Saudi Med J 2003; Vol. 24 (10): 1052-1054 roximal spinal muscular atrophy (SMA) is a neuromuscular disorder, which results in the loss of motor neurons in the spinal cord and lower brainstem leading to symmetrical progressive paralysis with muscle atrophy. Spinal muscular atrophy is classified into 3 clinical groups based on age at onset, achievement P ABSTRACT Molecular analysis of the spinal muscular atrophy and neuronal apoptosis inhibitory protein genes in Saudi patients with spinal muscular atrophy Mohammed Al-Jumah, MD, Ramanath Majumdar, PhD, Saad Al-Rajeh, MD, Adnan Awada, MD, Enrique Chaves-Carballo, MD, Mustafa Salih, MD, Saad Al-Shahwan, MD, Khalid Al-Subiey, MD, Shifa Al-Uthaim, BSc. of developmental milestones and lifespan. 1 Type I SMA, known as Werdnig-Hoffmann disease (the most severe form of SMA), is characterized by severe generalized muscle weakness and hypotonia with onset between birth and 6 months. Death from respiratory failure usually occurs within the first 2 years. In type II Objective: Spinal muscular atrophy (SMA) is a common, often fatal, autosomal recessive disease leading to progressive muscle wasting and paralysis as a result of degeneration of anterior horn cells of the spinal cord. The prevalence of SMA cases in the Kingdom of Saudi Arabia (KSA) is much higher than the European and North American population. Deletions or mutations in 2 genes, telomeric form of the survival motor neuron (SMN1) and the neuronal apoptosis inhibitory protein (NAIP), are known to be associated with SMA. The aim of this study is to examine the deletions or interruptions of the SMN1 and NAIP genes in Saudi patients. Methods: The study included 121 Saudi SMA patients [type I (60 patients); type II (26 patients); and type III (35 patients)]. The deletions or interruptions of the SMN1 and NAIP genes were detected by using polymerase chain reaction. The study was carried out at the King Fahad National Guard Hospital, Riyadh, KSA between 2000 and 2002. From the Neurogenetics Laboratory & Neurology Section (Al-Jumah, Majumdar, Awada, Al-Subiey, Al-Uthaim), King Fahad National Guard Hospital, Neurology & Neuropediatric Division (Al-Rajeh, Salih) King Saud University, Department of Neurosciences (Chaves- Carballo), King Faisal Specialist Hospital & Research Centre and the Department of Pediatrics (Al-Shahwan), Armed Forces Hospital, Riyadh, Kingdom of Saudi Arabia. Received 12th May 2003. Accepted for publication in final form 15th July 2003. Address correspondence and reprint request to: Dr. Mohammed Al-Jumah, Neurogenetics Laboratory (Mail code 2216), King Fahad National Guard Hospital, PO Box 22490, Riyadh 11426, Kingdom of Saudi Arabia. Tel. +966 (1) 2520088 Ext. 6665. Fax. +966 (1) 2520088 Ext. 6662. E-mail: jumahm@ngha.med.sa 1052 Articles