A 6-month-old boy is brought to the emergency department after a generalized tonic-clonic … — USMLE Step 2 CK

A 6-month-old boy is brought to the emergency department after a generalized tonic-clonic seizure. His mother reports that he has been increasingly irritable and "clammy" over the last several weeks, particularly in the early mornings before his first feeding. The infant was born at full term. Developmentally, he sits with pelvic support and rolls front-to-back, which his parents worry is delayed compared to his older sister.

Vital signs show a temperature of 36.8°C (98.2°F), heart rate of 155/min, blood pressure of 85/50 mm Hg, and respiratory rate of 52/min. Physical examination reveals a lethargic infant with a round, "doll-like" face and thin extremities. His abdomen is markedly distended with a firm, smooth liver edge palpable 6 cm below the right costal margin. The spleen is not palpable. Several small, yellowish papules are noted on the extensor surfaces of his arms and legs.

Initial laboratory studies show:

Test	Result
Sodium	138 mEq/L
Potassium	4.1 mEq/L
Chloride	104 mEq/L
Bicarbonate	11 mEq/L
Blood urea nitrogen	12 mg/dL
Creatinine	0.3 mg/dL
Glucose	42 mg/dL
Lactic acid	8.2 mmol/L (Normal: 0.5-2.2)

Arterial blood gas (room air):

Test	Result
pH	7.23
pCO2	24 mm Hg
pO2	95 mm Hg

Additional testing reveals markedly elevated serum triglycerides and uric acid.

Which of the following is the most appropriate intervention for this patient?

A
Endotracheal intubation and mechanical ventilation
B
Administration of nebulized albuterol
Frequent administration of uncooked cornstarchCevap
D
Referral for early intervention physical therapy
E
Initiation of intravenous acyclovir

Cevap

The correct intervention is the frequent administration of uncooked cornstarch.

The correct intervention is the frequent administration of uncooked cornstarch. This patient's presentation of early-morning (fasting) hypoglycemia, seizures, massive hepatomegaly without splenomegaly, 'doll-like' facies, lactic acidosis, and eruptive xanthomas is pathognomonic for Glucose-6-phosphatase deficiency (Von Gierke disease, Glycogen Storage Disease Type I). Because these patients cannot synthesize glucose from glycogen breakdown or via gluconeogenesis, they rely entirely on continuous exogenous carbohydrate intake. The primary goal of management is to avoid fasting, which prevents hypoglycemia and the secondary cascade of lactic acidosis and hyperuricemia (caused by substrate diversion). Frequent administration of uncooked cornstarch provides a steady, slow-release source of intestinal glucose, effectively preventing metabolic crises.

Adım Adım Çözüm

Interpret the clinical presentation and laboratory findings.

The patient has fasting hypoglycemia, severe lactic acidosis, hepatomegaly without splenomegaly, "doll-like" facies, and eruptive xanthomas.

These are the classic hallmarks of Glucose-6-phosphatase deficiency (Von Gierke disease or Glycogen Storage Disease Type I).

Evaluate the patient's acid-base status and respiratory rate.

The patient has a normal anion gap of 23 (138 - [104 + 11]). Winter's formula (1.5 × 11 + 8 ± 2) predicts a pCO2 of 22.5 to 26.5 mm Hg. The actual pCO2 of 24 mm Hg indicates perfect respiratory compensation.

Calculating expected compensation prevents mistakenly diagnosing an impending respiratory failure or primary pulmonary pathology.

Evaluate the patient's developmental milestones and skin findings.

Sitting with support and rolling are normal for a 6-month-old. The yellowish papules are eruptive xanthomas from severe hypertriglyceridemia, not an infection.

Accurate recognition of normal milestones and metabolic skin findings rules out unnecessary physical therapy and antimicrobial treatments.

Determine the optimal management strategy for the underlying disease.

Select frequent administration of uncooked cornstarch.

Because patients with GSD I cannot produce glucose via glycogenolysis or gluconeogenesis, providing a slow-release complex carbohydrate (cornstarch) prevents hypoglycemia and secondary lactic acidosis.

Anahtar Kavram

Glucose-6-phosphatase deficiency (Von Gierke disease) presents at 3 to 6 months of age with severe fasting hypoglycemia, hepatomegaly, lactic acidosis, hyperuricemia, and hyperlipidemia, and is managed long-term by avoiding fasting with complex carbohydrates like uncooked cornstarch.

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