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Acro‐Osteolysis and Symphalangism Mutations

We reported a very rare case of a 57-year-old female who had adult-onset noncongenital idiopathic acro-osteolysis combined with proximal symphalangism, together with shortening of fingers, hands, and toes. Radiological examination revealed bone resorption and partial loss of fingers and phalanges. Although the cause and pathogenesis of the “combination” of these two abnormalities were likely to be multifactorial, previous reports could not explain it exactly. Because the symphalangism was reported to be involved by the mutation of Noggin gene (NOG), known to be a bone morphogenetic protein (BMP) antagonist, we performed mutation analysis of the NOG of the patient by long and accurate PCR method of six primers, according to the published sequence of NOG (NCBI Reference Sequence HSU31202) and the current recommendation for mutation nomenclature (available at http://archive.uwcm. ac.uk/uwcm/mg/hgmd0.html). The current case represented some missense mutations (173 G > T, 176 A > T, 180 A > T, 203 C > G, 208 C > G) and a deletion (14 del T) in Nog. However, we did not obtain complete results, because we could not specify the consequences of the DNA alterations on the amino acid level or exclude the possibility that the sequence alterations are polymorphisms. Thus, we concluded that the observed sequence alterations could only imply causation. One of the purposes of the report was to present the very rare case and to seek information to correctly implicate the pathogenesis of the combination of adult-onset noncongenital acro-osteolysis and proximal symphalangism. However, we have not made much progress in the study, and nothing has been resolved in the patient yet. Therefore, Dr Debeer’s comments are highly appreciated and encourage us to perform further analyses to confirm the presence of NOG mutations in the symphalangism, one of two abnormalities in this patient. Also, we will continue to ask for any suggestions that explain the mechanisms of this very rare case.