Alström Syndrome Diagnostic Criteria — Clinical Guide

The diagnosis of Alström Syndrome relies on age-stratified clinical criteria first proposed by Marshall and colleagues and later refined in the 2020 international consensus management guidelines.¹ ² This article lays out those criteria, explains how they're applied, and shows how genetic testing fits into the diagnostic decision.

Alström unfolds in waves. A 1-year-old who has cone-rod dystrophy and dilated cardiomyopathy looks very different from a 20-year-old who has lost vision, developed hearing loss, become obese, and developed type 2 diabetes — yet both have the same underlying ALMS1 mutations. Stratified criteria let clinicians apply the right pattern at the right age.

The age bands used in the consensus framework are:

• Birth to 2 years
• 3 to 14 years
• 15 years and older

For each band, criteria are divided into major and minor categories. Different combinations make a clinical diagnosis "definite," "probable," or "possible," with genetic confirmation always being the gold standard.

These features are highly suggestive of Alström and weight diagnosis most heavily:

1. *Two pathogenic variants identified in ALMS1* (or homozygous in consanguineous families) 2. Family history — a sibling, child, or parent with confirmed Alström Syndrome 3. Cone-rod dystrophy** — confirmed on ERG, with characteristic photophobia and nystagmus

These features support the diagnosis when present alongside major findings:

• Obesity (truncal, beginning in the first 1–3 years)
• Dilated cardiomyopathy in infancy (acute onset, often with congestive heart failure)
• Adolescent or adult-onset cardiomyopathy
• Sensorineural hearing loss
• Hepatic dysfunction (elevated transaminases, NAFLD on imaging)
• Renal dysfunction (proteinuria, declining eGFR)
• Hyperinsulinemia, insulin resistance, or type 2 diabetes mellitus
• Hypertriglyceridemia
• Short stature in adulthood (below 25th centile)
• Hypogonadism, or pubertal delay/arrest
• Pulmonary problems (recurrent infections, asthma-like symptoms in childhood; pulmonary fibrosis or hypertension in adults)
• Urologic dysfunction (especially in females in their late teens)
• Developmental delay (gross or fine motor milestones)
• Scoliosis or other significant musculoskeletal findings
• Acanthosis nigricans

Birth to 2 years

A diagnosis is possible with two minor criteria. A diagnosis is probable with major criterion (cone-rod dystrophy) plus one minor criterion. A diagnosis is definite with two major criteria, or with one major plus genetic confirmation.

In this age group, the most useful clinical pairing is cone-rod dystrophy plus dilated cardiomyopathy, present together in many newly-diagnosed infants.³

3 to 14 years

By mid-childhood, more features have usually emerged. A diagnosis is probable with one major criterion plus two minor criteria, and definite with two major criteria. Common pairings at this age include cone-rod dystrophy with sensorineural hearing loss, with obesity, or with elevated insulin/glucose.

15 years and older

In adolescents and adults, the multisystem pattern is usually well-developed. A diagnosis is probable with one major plus four minor criteria, and definite with two major criteria including genetic confirmation. By this stage, most affected individuals have at least 5–6 minor features and a clearly multisystem clinical picture.⁴

The criteria perform well in classical cases but can miss atypical presentations:

• Single-system presentations — A baby with isolated dilated cardiomyopathy may have the genetic diagnosis confirmed before any other feature appears. The criteria don't capture this well, but rapid trio genetic testing in the NICU now picks up these cases earlier than the criteria would suggest.
• Adults diagnosed late — Some adults are diagnosed in their 30s or 40s after years of being labeled with separate conditions (cardiomyopathy, retinitis pigmentosa, Bardet-Biedl). When the genetic test is positive, the diagnosis is made even if a strict criteria score would not have triggered earlier.
• Atypical phenotypes — Some adults without obesity have been described, complicating the classic picture.⁵

For these reasons, low-threshold genetic testing is increasingly favored when any combination of cone-rod dystrophy, infantile cardiomyopathy, sensorineural hearing loss, or severe insulin resistance is present.

In a multidisciplinary clinic, a typical workflow is:

1. Clinical assessment identifies a suspicious phenotype. 2. Targeted testing — ERG, echocardiogram, audiology, metabolic panel — confirms which Alström features are present. 3. Criteria are applied to determine probability — "definite," "probable," or "possible." 4. Genetic testing is ordered to confirm. In most jurisdictions, an ALMS1 sequencing test is the first-line genetic study. 5. Diagnosis is made and surveillance begins for any system not yet involved.

A patient who meets "probable" or even "possible" criteria still warrants genetic testing — the diagnostic criteria are designed to flag candidates for testing, not to replace it.

The diagnostic criteria help separate Alström from other ciliopathies and overlapping conditions, but the differential typically includes:

• Bardet-Biedl Syndrome — distinguished by polydactyly and intellectual disability
• Usher Syndrome — distinguished by absence of cardiomyopathy, no obesity, no diabetes
• Wolfram Syndrome (DIDMOAD) — distinguished by diabetes insipidus and optic atrophy
• Cohen Syndrome — distinguished by intellectual disability and characteristic facial features
• Leber Congenital Amaurosis — distinguished by absence of systemic features

A 2011 paper showed that systematic ciliopathy gene sequencing reliably distinguishes Alström from Bardet-Biedl in cases where clinical features overlap.⁶

• Alström Syndrome Diagnosis Hub
• How Is Alström Syndrome Diagnosed?
• Why Alström Syndrome Is Often Misdiagnosed
• ALMS1 Mutations: Understanding Your Genetic Test Report
• Alström vs Bardet-Biedl Syndrome

April 30, 2026.