Session: SAT 199-223-Disorders of Bone & Calcium Homeostasis: Case Reports
Poster Board SAT-205
Clinical case: The subject presented at 13 years of age for evaluation of left knee pain that persisted over several months. He had a history of loss of four lower incisors in childhood but was not evaluated for skeletal abnormalities. Parents denied consanguinity. The patient’s height and linear growth rate were normal. The left knee had full range of motion and there were no joint deformities. Radiograph of left knee indicated two oval radiolucent lesions in the femoral metaphysis. A similar oval radiolucent area was also present in the humerus. An MRI of lower extremities indicated mild soft tissue swelling of left knee joint and an increased signal in the distal metaphysis and distal diaphysis both femurs. The ESR was abnormally elevated and serum alkaline phosphatase activity (17 U/L; normal 42-362) was subnormal. Both thyroid function and serum zinc level were normal. Serum pyridoxal 5’-phosphate was abnormally elevated (258 mcg/L, normal range 5-50). Sequence analysis of ALPLgene indicated a homozygous missense mutation, c.1077 C>G (p. Ile359Met).
Conclusion: This case adds to information about the broad spectrum of symptoms, radiographic findings, and gene mutation in childhood hypophosphatasia. Pain, joint swelling and elevated ESR were mostly likely due to inflammation caused by accumulation of inorganic pyrophosphate. Oval radiolucent skeletal lesions are an unusual radiographic finding in childhood hypophosphatasia, and indeed were initially considered suspicious for malignancy until biochemical analysis indicated the diagnosis. Another case of homozygous mutations of ALPL was described recently in a child with a mild form of hypophosphatasia (1), but to the best of our knowledge this finding is extremely rare. The case we report also indicates that the effect of homozygous mutation in ALPL may be modified by other factors and result in a mild form of hypophosphatasia.
Nothing to Disclose: SU, SSG, JH, BJV, GDB
*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm
See more of: Abstracts - Orals, Featured Poster Presentations, and Posters