Strong variable clinical presentation in 3 patients with 7q terminal deletion.

We report 3 patients with a 7q terminal deletion. The first, a 7 weeks old female, with a de novo 7q36-->qter deletion, was microcephalic and had a partial hypoplasia of the corpus callosum on the MRI-scan of the brain. The second, a 3 months old male, showed microcephaly, disproportionate growth retardation, truncal obesity and facial dysmorfism giving the clinical impression of a "microcephalic primordial dwarfism (osteodysplastic type)". At the age of 6 months he had developed a single maxillary central incisor suggesting a minimal form of holoprosencephaly (HPE). Additional FISH-studies showed a 7q36.1-->qter deletion, as the unbalanced product of a t(5;7)(q35.2;q36.1)pat. The de novo 7q36-->qter deletion in the third patient, a 5 years old female, was associated with borderline intelligence, mild microcephaly, small midface, choanal narrowing and a single maxillary central incisor as a minimal form of HPE. CT- and MRI-scan of the brain were normal. In these 3 patients extensive FISH analysis was performed to investigate the possible involvement of the HPE gene region on chromosome 7q36. The target gene for HPE, the Sonic hedgehog gene (SHH) as well as several other genes important for normal brain development (En2;HOX1,HTR5A) were found to be deleted in all three patients. Our findings stress the importance of 7q36 microdeletion studies in patients with even minimal signs of HPE, as relative microcephaly with small midface (choanal narrowing), agenesis/hypoplasia of the corpus callosum/septum pellucidum, thalamic fusion or a single maxillary central incisor.