Merienne et al. (1998) evaluated both immunoblot and RSK2 kinase assays as diagnostic tests for Coffin-Lowry syndrome using cultured lymphoblastoid or fibroblast cell lines. Western blot analysis failed to detect RSK2 protein in 6 patients, suggesting the presence of truncated proteins. This conclusion was confirmed in 4 patients, in whom the causative mutations, all leading to premature termination of translation, were identified. Of 4 patients showing normal amounts of RSK2 protein on Western blot and tested for RSK2 phosphotransferase activity, 1 had impaired activity. Analysis of RSK2 cDNA sequence in this patient showed a mutation of a putative phosphorylation site that would be critical for RSK2 activity. Merienne et al. (1998) concluded that both assays were reliable and rapid methods for diagnosis of Coffin-Lowry syndrome, and that, at least, the Western blot analysis could be used directly on lymphocyte protein extracted directly from blood samples.
Cholesterol granuloma of the petrous apex is a newly recognized clinical entity distinct from cholesteatoma. Cholesterol granuloma usually produces symptoms of trigeminal, facial, and abducens nerve palsy and may not affect the auditory nerve. The characteristic computerized cranial tomographic (CCT) finding is a nonenhancing, smooth-walled, expansile lesion that is isodense with brain tissue in a patient with bilaterally well pneumatized mastoids and petrous apices. Treatment is limited to drainage of the cyst and insertion of a stent for permanent aeration of the petrous apex. Of ten cases of cholesterol granuloma of the petrous apex recently diagnosed at the Otologic Medical Group, the correct preoperative diagnosis was made in nine patients on the basis of CCT findings. Six of the nine patients had serviceable hearing preoperatively; serviceable hearing was maintained postoperatively in five patients.