A rare co-occurrence of duchenne muscular dystrophy, congenital adrenal hypoplasia and glycerol kinase deficiency due to Xp21 contiguous gene deletion syndrome: case report

BACKGROUND

Contiguous gene deletion syndromes are rare genomic disorders caused by deletion of large segments of DNA resulting in co-occurrence of apparently unrelated multiple clinical phenotypes. We report a boy with contiguous gene deletion involving Xp21 genomic location.

CASE PRESENTATION

A Sri Lankan boy with developmental delay and failure to thrive first presented at three years of age with hypovolaemia, hyperpigmentation and drowsiness. Investigations done at that time revealed hypoglycaemia, hyponatraemia, hyperkalaemia, low cortisol, low aldosterone, high ACTH and low 17-hydroxyprogesterone. He was diagnosed to have primary adrenal insufficiency. During follow-up at five years, he was noted to have progressive difficulty in walking, waddling gait, hypotonia, calf hypertrophy and positive Gower's sign. His creatine kinase was very high, and the electromyogram showed myopathy. Genetic analysis revealed hemizygous deletion involving the final 35 exons of the dystrophin gene confirming the diagnosis of Duchenne muscular dystrophy. Further investigations revealed pseudohypertriglyceridemia, large glycerol peak on urine organic acid analysis and hemizygous deletion of the glycerol kinase gene confirming glycerol kinase deficiency. Based on the presence of Duchenne muscular dystrophy, glycerol kinase deficiency and probable congenital adrenal hypoplasia along with genetic confirmation of deletions involving dystrophin and glycerol kinase genes, the diagnosis of Xp21 contiguous gene deletion syndrome was made.

CONCLUSIONS

We report a child with contiguous gene deletion syndrome who was initially diagnosed as having isolated primary adrenal insufficiency probably due to congenital adrenal hypoplasia. Later he was confirmed to have Duchenne muscular dystrophy and glycerol kinase deficiency, as well. This case report highlights the importance of pre-emptive evaluation and identification of genetic defects when patients present with seemingly unrelated diseases that could aid in accurate diagnoses of contiguous gene deletion syndromes.

Beyond the adrenals: Organ manifestations in inherited primary adrenal insufficiency in children

Primary adrenal insufficiency (PAI) in children is mostly due to genetic defects. The understanding of the molecular genetics of the causes of adrenal insufficiency in the pediatric population has made significant progress during the last years. It has been shown that inherited PAI can lead to certain clinical manifestations and health problems in children beyond the adrenals. Organ dysfunctions associated with different forms of PAI in children include a wide range of organs such as gonads, brain, heart, bone, growth, bone marrow, kidney, skin, parathyroid, and thyroid. Diagnosing the correct genetic cause of PAI in children is therefore crucial to adequately control long-term treatment and follow-up in such patients.

[Recurrent anorexia and pigmentation of skin for more than two months in an infant]

A 2-month-old boy presented with adrenal insufficiency, impaired liver function, hypertriglyceridemia, significantly elevated creatine kinase and electrolyte disturbance. Microarray comparative genomic hybridization (aCGH) analysis test showed a pathogenic 8.7 Mb deletion in the short arm of chromosome X (Xp21.3 - p21.1) and confirmed the diagnosis of complex glycerol kinase deficiency (cGKD). He was treated with hydrocortisone, coenzyme Q10 and L-carnitine and was subsequently followed up for 4 years. His serum cortisol levels returned to normal one week later after treatment, but the serum creatine kinase, triglyceride and aminotransferase levels were progressively increased along with mental retardation and decreased muscular strength. cGKD is also named as Xp21 contiguous gene syndrome. The clinical manifestations of this disease include hypertriglyceridemia, congenital adrenal hypoplasia (AHC), Duchenne muscular dystrophy, and mental retardation. This case highlights the necessity to screen the serum triglyceride and creatine kinase levels in infants with suspected adrenal insufficiency.