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Open access

Mike Lin and Kirtan Ganda

Summary

We present the case of a 60-year-old female who developed repeated atraumatic stress fractures. She was initially diagnosed with osteoporosis based on her dual-energy X-ray absorptiometry (DXA) scan bone mineral density (BMD) T-scores and started on denosumab therapy. Secondary osteoporosis screen revealed abnormal myeloma screen and low serum phosphate levels. It was thought that the patient had multiple myeloma with associated Fanconi-related tubular dysfunction. However, fibroblast growth factor-23 (FGF-23) levels were grossly elevated, making Fanconi syndrome unlikely. The patient was subsequently diagnosed with two separate conditions, namely cardiac amyloid light-chain (AL) amyloidosis and FGF-23-related hypophosphataemia, likely due to tumour-induced osteomalacia. This case highlights the importance of excluding osteomalacia as a cause of low BMD and checking FGF-23 levels in the workup for hypophosphataemia.

Learning Points

  • Tumour-induced osteomalacia is a difficult diagnosis as the tumour is often small and slow growing. Imaging may fail to identify a tumour, and treatment therefore consists of calcitriol and phosphate replacement.

  • Tumour-induced osteomalacia should be suspected in the adult presenting with new-onset hypophosphataemia, elevated FGF-23 levels and isolated renal phosphate wasting.

  • Serum phosphate is not part of the routine chemistry panels. Routinely checking phosphate levels prior to initiating antiresorptive therapy is warranted.

  • DXA cannot distinguish low bone mineral density due to osteoporosis from osteomalacia. Antiresorptive therapy should be avoided in osteomalacia due to the risk of clinical and radiographic deterioration.

Open access

Avinash Suryawanshi, Timothy Middleton, and Kirtan Ganda

Summary

X-linked adrenoleukodystrophy (X-ALD) is a rare genetic condition caused by mutations in the ABCD1 gene that result in accumulation of very long chain fatty acids (VLCFAs) in various tissues. This leads to demyelination in the CNS and impaired steroidogenesis in the adrenal cortex and testes. A 57-year-old gentleman was referred for the assessment of bilateral gynaecomastia of 6 months duration. He had skin hyperpigmentation since 4 years of age and spastic paraparesis for the past 15 years. Physical examination findings included generalised hyperpigmentation (including skin, buccal mucosa and palmar creases), blood pressure of 90/60 mmHg, non-tender gynaecomastia and bilateral hypoplastic testes. Lower limb findings were those of a profoundly ataxic gait associated with significant paraparesis and sensory loss. Primary adrenal insufficiency was confirmed and investigations for gynaecomastia revealed normal testosterone with mildly elevated luteinising hormone level and normal prolactin. The combination of primary adrenal insufficiency (likely childhood onset), partial testicular failure (leading to gynaecomastia) and spastic paraparesis suggested X-ALD as a unifying diagnosis. A serum VLCFA panel was consistent with X-ALD. Subsequent genetic testing confirmed the diagnosis. Treatment with replacement doses of corticosteroid resulted in improvement in blood pressure and increased energy levels. We have reported the case of a 57-year-old man with a very late diagnosis of X-ALD manifested by childhood onset of primary adrenal insufficiency followed by paraparesis and primary hypogonadism in adulthood. Thus, X-ALD should be considered as a possibility in a patient with non-autoimmune primary adrenal insufficiency and neurological abnormalities.

Learning points

  • Adult patients with X-ALD may be misdiagnosed as having multiple sclerosis or idiopathic spastic paraparesis for many years before the correct diagnosis is identified.

  • Screening for X-ALD with a VLCFA panel should be strongly considered in male children with primary adrenal insufficiency and in male adults presenting with non-autoimmune primary adrenal insufficiency.

  • Confirmation of a genetic diagnosis of X-ALD can be very useful for a patient's family as genetic testing enables detection of pre-symptomatic female heterozygotes who can then be offered pre-natal testing to avoid transmission of the disease to male offsprings.