UN.

CHEM.

40/11,

2099-2103

(1994)

ongenital Adrenal Hypoplasia, Duchenne Muscular )eficiency: Importance of Laboratory Investigations 3ene Deletion Syndrome avid onia

E. C. Cole,”3 Salisbury’

Lorne

A.

Clarke,’

D.

Christie

Riddell,’

Ve describe an infant with adrenai insufficiency who was ubsequently diagnosed with Duchenne muscular dystrophy DMD) and hyperglycerolemia due to glycerol kinase deliiency. Karyotyping showed a deletion on the short arm of the chromosome (p21.1 to p22.1). Molecular mapping revealed iat the deletion extended from the 3’ end of the DMD gene a site telomeric to the loci for X-linked congenital adrenal ypoplasia and glycerol kinase deficiency. These results are iagnostic for an Xp21 contiguous gene deletion synrome-so named because the deletion manifests as a disnctive cluster of otherwise unrelated single-gene disorders in ie same indMdual. The Xp21 syndrome should be considred inany infant with adrenal insufficiency. Measurement of erum tnglycendes (without glycerol blanking) and creatine iriase activity are simple screening tests that may facilitate any diagnosis and appropriate genetic counseling about sks of recurrence in subsequent offspring. idexlng Terms: adrenal insufficiency/chromosomal able

disorders/pediatric

mapping/her-

chemistry

Coincident expression of otherwise unrelated inborn erof metabolism may oocur as a result of a large, mu!iple-gene deletion, referred to as a contiguous gene deleion syndrome (1-4). The study of affected patients is tseful in localizing and determining the order of specific nes. The routine clinical laboratory may play an imporant part in identifying these associations and signifiantly influence the quality of care (5). We describe an nfant with congenital adrenal hypoplasia (CAH)4 in rhom suspicion of Duchenne muscular dystrophy (DMD) ad to the diagnosis of an Xp21 contiguous gene deletion yndrome (6) and identification of coincident glycerol kiors

of Pediatrics and Pathology, Dalhousie UniverNova Scotia, Canada B3H 3G9. Department of Pediatrics, University of Colorado School of ledicine, Denver, CO 80262. 3Mdress for correspondence: Department of Clinical Biochemistry, rniversity of Toronto, 100 College St., Rm. 415, Toronto, Ontario, Canda M5G 1L5. Fax 416-978-5650, E-mail [email protected] Nonstandard abbreviations: DMD, Duchenne muscular dystrohy; GK, glycerol kinase; PCR, polymerase chain reaction; ACTH, drenocorticotropic hormone (corticotropin); GnRH, gonadotropineleasing hormone (gonadoliberin); FSH, follicle-stimulating ormone (follitropin); LH, luteinizing hormone (lutropin); CK, cretine kinase; CAll, congenital adrenal hyperplasia; AHC, -linked congenital adrenal hypoplasia; and FISH, fluorescent in itu hybridization. Received March 4, 1994; accepted August 12, 1994 Departments itr, Halifax,

Karen

Dystrophy, and Glycerol Kinase in Delineating a Contiguous A.

Samson,’

William

nase (GK EC 2.7.1.30) deficiency molecular studies used to confirm the deletion in this child. Case

K. Seltzer,2

and

(7). We also describe and map the extent

the of

Report

A male

infant was delivered at 39 weeks’ gestation by section without significant perinatal complications. He first came to medical attention at age 16 days because of feeding difficulties, dehydration, and a weight loss of 680 g from a birth weight of 2750 g. His response to rehydration was hyponatremia (128 mmol/L) and hyperkalemia (9.6 mmol/L), prompting a working diagnosis of CAH. Subsequent investigation revealed decreased plasma aldosterone [110 pmol/L (reference range 970-3610 pmol/L)], decreased plasma dehydroepiandrostenedione sulfate [0.2 tmol/L (4.3-9.5 moVL)], and normal plasma 17a-hydroxyprogesterone [11.4 nmol/L (550 nmolfL). Serum testosterone was 5.9 nmoL’L (reference range for children, >0.2 nmol/L). Serum fofficle-stimulating hormone (FSH) was 5.4 lU/L (reference range for infants, 1-12 lU/L), and serum luteinizing hormone (LH) concentrations at ages 16 and 38 days were 9.4 and 30.6 lU/L, respectively (reference values for infants, 22 ± 13 lU/L). Fludrocortisone treatment corrected the electrolyte abnormalities, and the patient improved and was discharged home. He was seen periodically for management of his adrenal insufficiency. Over the next few months, the ACTH-stimulated concentrations of plasma cortisols declined. At age 9 months, his baseline and ACTH-stimulated cortisol concentrations were 181 and 173 nmol/L, respectively, confirming the diagnosis of CAH. Subsequently, cortisone acetate was added to the treatment regimen, leading to further improvement in motor strength and well-being. Mineralocorticoid and glucocorticoid replacement has been continued since. At 13 months, the child was noted to have an exotropia and mild hypertelorism, but his vision was not assessed in detail. Skin pigmentation was normal but bilateral cryptorchidism was observed. At age 2 years, surgical exploration revealed intraabdominal, atrophic stimulation

tropin) to 737 cortisol

CLINICAL

CHEMISTRY,

Vol. 40, No. 11,

1994

2099

testes 0.3 and 0.4 cm in diameter. After the removal of all testicular tissue, baseline and gonadotropin-releasing hormone (GnRH)-stimulated concentrations of FSH and LH were undetectable, suggestive of hypogonadotropic hypogonadism (8). Although initially this child was thought to be hypertonic

and

visually

impaired,

his

vision

improved

while

his muscle tone decreased. Developmental delay and growth failure were mild but persistent and progressive. At age 2.7 years, his call’ muscles were noted to be enlarged. Serum total creatine kinase (OK) activity was 21 150 U/Land a skeletal muscle biopsy was histopathologically consistent with DMD. The possibility was considered that he might have an unusual X-linked disorder of retinal rod cells, called incomplete stationary night blindness (akin to Aland Island disease or Forsius-Eriksson-Miyake syndrome) (9, 10). However, evidence now suggests that deletions in the dystrophin gene can result in failure to express a retina-specific form

of the

leading to characteristic clinical and electroretinographic changes in vision (11). At this point, the diagnosis of a contiguous gene deletion syndrome was entertained, and additional studies were undertaken to confirm the diagnosis. Methods

DM1)

dystrophin

protein,

and Results

Karyotyping. lymphocytes were reported

Chromosomes from peripheral blood examined by routine metaphase banding as normal (46,XY). Repeat karyotyping

and examination of extended resolution) revealed a small

chromosomes (-550-band interstitial deletion of the X

chromosome in the p21.3 region (Fig. 1). Because the child had been adopted, the mother could not be tested. The prophase karyotype of a biological sister, also

AHC u-a u-a

GKD

11.4

“-3 II II 11.1. II

CYBB

l

OTC

tography-mass Mamer, Montreal,

spectrometry QU), was

(5) (courtesy of 4910 mg/g creatinine

‘3 211

‘l.a

q

as substrate and quantifying the formation product. Assay reactions (100 L) contained sample sonicate (50 g of protein), 100 mmoIJL (pH 7.4 at 37#{176}C),1.0 mmol/L EDTA, 4 mmol/L 20 mmol/L 2-mercaptoethanol, mmol/L ATP, and 50 mol/L 1) indicate that the activity

of labelei 20 iL o Tnis-HC MgSO4

6.25 mmol/L NaF, glycerol. The results (Tabb in our patient was