The female infant was born to healthy non-consanguineous parents (25-year-old father, and 22-year-old mother) after an uncomplicated first pregnancy and 40 weeks of gestation. A Cesarean section was performed due to a failed vaginal delivery, but the Apgar score until 15 min after birth and birth weight was normal (3,300 g). The patient was intubated after developing progressive tachypnea, moaning, and severe hypoglycemia (0.9 mmol/L). The patient developed hyperbilirubinemia that was unresponsive to phototherapy, but the parents took the baby home, for home care at the age of 9 days.
At the age of 1.4 months, the patient was admitted to a provincial hospital for jaundice, vomiting, afebrile seizures, and pneumonia. The lowest blood glucose level during the hospital stay was 1.4 mmol/L. The serum cortisol levels were extremely low (13.8-29.3 nmol/L, normal range 138-690 nmol/L) while adrenocorticotropic hormone levels were slightly lower or normal (6.0-18.5 pg/ml, normal range 6.4-40 pg/ml). A cortisol deficiency was diagnosed, but parents refused hormone replacement therapy. The patient was discharged after the pneumonia was resolved and blood glucose levels were stabilized.
At the age of 3.2 months, the patient was presented to our hospital for cholestasis without obvious symptoms of hypoglycemia, infection, alacrima, or achalasia. Repeated morning serum cortisol levels were extremely low (8.8-10.6 nmol/L, normal range 138-690 nmol/L), while ACTH was extremely elevated (1656.9-1911.8 pg/ml, normal range 6.4-40 pg/ml). Upon physical examination, significant jaundice, skin hyperpigmentation and slight hepatosplenomegaly (liver 2-2.5 cm below the right costal margin, and 2.5 cm below the xiphoid process; spleen 1.5-2.0 cm below the left costal margin) were observed. Slight dysmorphic features such as a transverse palmar crease in the right hand, a prominent forehead, hypertelorism (inner canthal distance greater than the palpebral fissure length) were noted. The palmar crease, and the changes in skin pigmentation are presented in Figure 1. Written informed consent was obtained from the parents for the publication of this case report and related images. Changes in body weight/length, complete blood count, procalcitonin, serum biochemistry, blood coagulation, and endocrine profiles throughout the disease course are provided in Table 1.
Genetic screening for abnormalities related to congenital adrenal hyperplasia (list of 44 genes are provided in Table 3), and multiplex ligation-dependent probe amplification (MLPA) analysis of the CYP21A2 gene were performed by a commercial genetic testing company (Customized target capture sequencing, http://www.mygenostics.com/ServiceTechnology.aspx?nid=263&pid=268). The result showed compound heterozygous variants in the melanocortin 2 receptor (MC2R) gene, but the result of the CYP21A2 gene MLPA analysis was negative for hot-spot mutations and copy number variants (Supplementary Figure 1). We conducted protein modeling with SWISS-model (https://www.swissmodel.expasy.org) using the most similar structure (5jtb.1.A, Adenosine receptor A2a), and polar contacts of wild-type and mutated amino acid residues were compared with Pymol software (https://pymol.org/2/). The c.433C>T/p.R145C was reported in the dbSNP152 (http://www.ncbi.nlm.nih.gov/snp/rs139218324), and gnomAD (http://gnomad-old.broadinstitute.org/variant/18-13885085-G-A), but not in the 1000 Genome Database (http://www.1000genomes.org/) and Exome Variant Server (http://evs.gs.washington.edu/EVS/). The c.712C>T/p.H238Y variant was not reported in the dbSNP152, gnomAD, 1000 Genome Database, and Exome Variant Server. The c.433C>T/p.R145C variant of maternal origin caused the change of arginine (polar, basic) at the amino acid position of 145 to cysteine (non-polar, neutral). R145 is a relatively conserved amino acid residue, and five out of eight in-silico prediction tools (Table 2) predicted this variant as pathogenic. This is a known disease-causing variant (HGMD CM116421, rs139218324), and reported to be associated with FGD1 in an adopted Chinese girl. Protein modeling showed no effect of R145C residue change on polar contact with V149. The c.712C>T/p.H238Y variant of paternal origin caused the change of amino acid residue histidine (polar, basic) at the position of 238 to tyrosine (polar, neutral). H238 is a strictly conserved residue, and all eight in-silico prediction tools predicted this variant as pathogenic (Table 2). Protein modeling showed that the H238Y mutation changed polar contact of the amino acid residue in the position of 238 with adjacent residues, and polar contact with N261 in the transmembrane domain (TMD) 7 was lost. Confirmation with Sanger sequencing, conservation status of amino acid residue that have been affected, protein modeling results, and in-silico pathogenicity prediction results for both MC2R variants are provided in Figure 2 and Table 2.
Extensive etiologic evaluations from birth until the last follow-up (4.9 months) are provided in Table 3. After ruling out other causes of hypoglycemia, cholestasis, and adrenal deficiency, a diagnosis of FGD1 was made. Oral hydrocortisone was started at a dose of 30 mg/m2 body surface area (divided into three doses) at the age of 3.4 months. Cholestasis was resolved at 4.9 months, skin hyperpigmentation was improved, and no further episodes of hypoglycemia occurred. Morning serum cortisol levels 1 h after hydrocortisone intake was normal, while ACTH levels returned to near normal levels. However, parents decided to stop the medication at the age of 7.4-months, and serum cortisol/ACTH levels returned to extreme levels at the age of 8.1-months (Table 1).