Nephronophthisis 1
Approximately 80% of patients with nephronophthisis (NPHP1; 256100) demonstrate a homozygous deletion of about 290 kb that encompasses the NPHP1 gene (Konrad et al., 1996; Hildebrandt et al., 1997; Saunier et al., 2000).
Senior-Loken Syndrome 1
Caridi et al. (1998) described Senior-Loken syndrome (SLSN1; 266900), the association of nephronophthisis with autosomal recessive retinitis pigmentosa, in patients with homozygous deletion of the NPHP1 gene.
Joubert Syndrome 4
In 2 sibs with a mild form of Joubert syndrome (JBTS4; 609583), Parisi et al. (2004) demonstrated homozygous deletion of the NPHP1 gene identical, by mapping, to that in subjects with nephronophthisis alone. A hallmark of that disorder is cerebellar vermis hypoplasia with prominent superior cerebellar peduncles, creating the 'molar tooth sign' (MTS) on axial MRI. Parisi et al. (2004) suggested that the MTS may be relatively common in patients with juvenile nephronophthisis without classic symptoms of JS.
In 4 patients with Joubert syndrome from 3 nonconsanguineous families, Parisi et al. (2006) identified homozygosity for deletion of the NPHP1 gene. The molar tooth sign in these patients had a distinctive appearance, with elongated but not thickened superior cerebellar peduncles.
